a novel of new charge iridium complexes for organic light

A NOVEL OF NEW CHARGE IRIDIUM COMPLEXES FOR

ORGANIC LIGHT-EMITTING DIODE

AND SENSOR APPLICATIONS

KATTALIYA MOTHAJIT

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR THE DEGREE OF MASTER OF SCIENCE

MAJOR IN CHEMISTRY

FACULTY OF SCIENCE

UBON RATCHATHANI UNIVERSITY

ACADEMIC YEAR 2016

COPYRIGHT OF UBON RATCHATHANI UNIVERSITY

2

UBON RATCHATHANI UNIVERSITY

THESIS APPROVAL

MASTER OF SCIENCE

MAJOR IN CHEMISTRY FACULTY OF SCIENCE

TITLE A NOVEL OF NEW CHARGE IRIDIUM COMPLEXES FOR ORGANIC

LIGHT-EMITTING DIODE AND SENSOR APPLICATIONS

AUTHOR MISS KATTALIYA MOTHAJIT

EXAMINATION COMMITTEE

DR. FILIP KIELAR CHAIRPERSON

ASST. PROF. DR. RUKKIAT JITCHATI MEMBER

ASST. PROF. DR. KITTIYA WONGKHAN MEMBER

ADVISORS

…………………………………………….…… ADVISOR

(ASST. PROF. DR. RUKKIAT JITCHATI)

……………………….……………...…..... ..……………….…………….……………...…......

(ASSOC. PROF. DR. UTITH INPRASIT) (ASSOC. PROF. DR. ARIYAPORN PONGRAT)

DEAN, FACULTY OF SCIENCE VICE PRESIDENT

FOR ACADEMIC AFFAIRS

COPYRIGHT OF UBON RATCHATHANI UNIVERSITY

ACADEMIC YEAR 2016

I

ACKNOWLEDGEMENTS

Firstly, I would like to acknowledge my advisor, Asst. Prof. Dr. Rukkiat Jitchati,

for allowing me to undertake this project, all the brilliant ideas, his enthusiasm, advice

and guiding me throughout the years. Thank for his support, patience, and

encouragement throughout my graduate studies. It is not often that one finds

an advisor and colleague that always finds the time for listening to the little problems

and roadblocks that unavoidably crop up in the course of performing research.

His technical and editorial advice was essential to the completion of this dissertation

and has taught me innumerable lessons and insights on the workings of academic

research in general. His advice was most valuable to understand the obtained results

and to determine the next steps for the research presented in this thesis. Many thank to

Dr. Somboon Sahasithiwat and Miss Laongdao Menbangpung for their content advice

and sharing their extensive knowledge of OLEDs fabrication and measurement.

Thank to Asst. Prof. Dr. Kittiya Wongkhan for advice and support me in every

problem especially in English and for writing my publication. I would like

to acknowledge Dr. Filip Kielar for their constructive comment and suggestion.

Thanks Prof. Dr. Suwabun Chirachanchai and his students at the Petroleum and

Petrochemical College, Chulalongkorn University for Mass measurements in my work.

And I would also like to thank Miss Benjawan Somchob and Mr. Witsanu Sombat

for fabrication of some OLEDs presented in my work.

I would like to thank to the Organometallic and Catalytic Center (OCC), Department

of Chemistry, Faculty of Science, Ubon Ratchathani University for the synthesis

facilities.

Thanks everyone in the OCC group for contributed and helped me to make this

research work possible at Ubon Ratchathani University. And finally, I must thank my

family for their love and personal support during my study.

Kattaliya Mothajit

Researcher

II

บทคดยอ

เรอง : สารเชงซอนของโลหะอรเดยมมประจชนดใหมเพอประยกตใชเปนไดโอดเรอง อนทรยและตวตรวจวด ผวจย : แคทลยา โมทะจตร ชอปรญญา : วทยาศาสตรมหาบณฑต สาขาวชา : เคม อาจารยทปรกษา : ผชวยศาสตราจารย ดร.รกเกยรต จตคต ค าส าคญ : สารเชงซอนของโลหะอรเดยม (III), ไดโอดเรองแสงอนทรย (OLEDs), ตวตรวจวด

งานวจยนไดรายงานการสงเคราะหสารประกอบเชงซอนของโลหะอรเดยม (III) ทมประจ 2 ชด สารเชงซอนเปาหมายทงหมดไดพสจนเอกลกษณทางโครงสราง ศกษาสมบตทางแสงและสมบต ทางเคมไฟฟา ชดท 1 ใชเปนไดโอดเรองแสงอนทรย (OLEDs) ไดแก [Ir(spiro)(ppy)2]PF6 (KM01), [Ir(spiro)(thio)2]PF6 (KM02), [Ir(spiro)(difluoro)2]PF6 (KM03) และ [Ir(spiro)(ppz)2]PF6 (KM04) โดยท spiro คอ 4,5-diaza-9,9´-spirobifluorene, ppy คอ 2-phenylpyridine, thio คอ 2-thiophenylpyridine, difluoro คอ 2´,4´-difluorophenyl pyridine และ ppz คอ 2´,4´-difluorophenyl 1H-pyrazole น า KM01-KM04 ไปขนรปเปนอปกรณ OLEDs โครงสรางเปน ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1 by mole)/TPBi/LiF/Al พบวา KM01 ใหประสทธภาพทางไฟฟา (current efficiency) สงสดท 1.72 cd/A และความสวางสงสด 2,027 cd/m2

ชดท 2 ใชเปนตวตรวจวด n-butylamine ทางส (colorimetric sensor) ไดแก [Ir(L1)(ppy)2]PF6 (NU02) และ [Ir(L2)(ppy)2]PF6 (KM09) โดยท L1 คอ dimethyl-2,2´-bipyridine-3,3´-dicarboxylate และ L2 คอ dimethyl-2,2´bipyridine-4,4´dicarboxylate จากศกษาการเปลยนแปลงสของสารละลายเชงซอนของโลหะอรเดยม พบวาเปลยนจากสแดง (528 นาโนเมตร) เปนสสม (450 นาโนเมตร) ในสภาวะกรด HCl (100 equiv.) และ n-butylamine (3 equiv.) หลงจากท าปฏกรยา 120 นาท

III

ABSTRACT

TITLE : A NOVEL OF NEW CHARGE IRIDIUM COMPLEXES FOR

ORGANIC LIGHT- EMITTING DIODE AND SENSOR

APPLICATIONS

AUTHOR : KATTALIYA MOTHAJIT

DEGREE : MASTER OF SCIENCE

MAJOR : CHEMISTRY

ADVISOR : ASST. PROF. RUKKIAT JITCHATI, Ph.D

KEYWORDS : IRIDIUM (III) COMPLEX, LIGHT EMITTING DIODE (OLEDs)

SENSOR

This study reported the synthesis of two charge iridium (III) complex series.

All of the target complexes were characterized and studied their photophysical and

electrochemical properties. In the first series, the complexes used for organic light-

emitting diode (OLEDs) were [Ir(spiro)(ppy)2]PF6 (KM01), [Ir(spiro)(thio)2]PF6

(KM02), [Ir(spiro)(difluoro)2]PF6 (KM03), and [Ir(spiro)(ppz)2]PF6 (KM04)

(spiro was 4,5-diaza-9,9´-spirobifluorene, ppy was 2-phenylpyridine, thio was

2-thiophenylpyridine, difluoro was 2´,4´-difluorophenylpyridine, and ppz was

2´,4´-difluorophenyl 1H-pyrazole). Then, KM01-KM04 were fabricated for OLED

devices based on ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1 by mole)/TPBi/LiF/Al.

It was found that KM01 showed maximum current efficiency at 1.72 cd/A and

brightness at 2,027 cd/m2. In the second series, the complexes used for colorimetric

n-butylamine sensor were [Ir(L1)(ppy)2]PF6 (NU02) and [Ir(L2)(ppy)2]PF6 (KM09)

(L1 was dimethyl-2,2´-bipyridine-3,3´-dicarboxylate and L2 was dimethyl-2,2´bipyridine-

4,4´dicarboxylate). It was found that the color of charge iridium(III) complex

changed from red (528 nm) to orange (450 nm) in condition HCl (100 equiv.) and

n-butylamine (3 equiv.) after 120 minutes of reaction.

IV

CONTENTS

PAGE

ACKNOWLEDGEMENTS I

THAI ABSTRACT II

ENGLISH ABSTRACT III

CONTENTS IV

LIST OF TABLES VI

LIST OF FIGURES VII

LIST OF APPREVIATIONS XII

CHAPTER 1 INTRODUCTION

1.1 Importance in research and development 1

1.2 Organic light emitting diodes (OLEDs) application 2

1.3 Chemical sensor application 11

1.4 Objectives of thesis 12

CHAPTER 2 LITERATURE REVIEWS

2.1 Literature reviews 14

CHAPTER 3 EXPERIMENTAL

3.1 Chemical 21

3.2 Instruments and general chemical characterization techniques 23

3.3 Experimental section 25

3.4 OLEDs device fabrication 35

3.5 Colorimetric sensor study 37

CHAPTER 4 RESULTS AND DISSCUSSIONS

4.1 Synthesis of N^N ligand 38

4.2 The charged iridium(III) complex 44

CHAPTER 5 CONCLUSIONS 62

V

CONTENTS (CONTINUED)

PAGE

REFERRENCES 64

APPENDICES

A Characterized data 71

B Conference and publications 88

CURRICULUM VITAE 94

VI

LIST OF TABLES

TABLE

PAGES

2.1 Summary performance of device in OLEDs 18

3.1 Chemicals for the synthesis 22

3.2 Chemicals for OLED devices 23

3.3 Instruments for characterization technique 24

4.1 Photophysical characteristics of KM01-KM04 solution 48

4.2 Electrochemical properties and energy levels of KM01-KM04 50

4.3 Summary of host-guest multi-layer OLED performances with

configurations of ITO/PEDOT:PSS/KM01-KM04: BMIMPF6

(1:1)/TPBi/LiF/Al

52

4.4 Summary of host-guest OLED device performances with

configurations of ITO/PEDOT:PSS/KM04:BMiMPF6(1:0.75)/

TPBi/LiF/Al

54

4.5 Summary of maximum absorption wavelength of NU02

in chemical sensor

60

VII

LIST OF FIGURES

FIGURE

PAGES

1.1 General structure of neutraliridium(III) complexes 1

1.2 General structure of chargeiridium(III) complexes 2

1.3 Examples of OLEDs displays in a market 3

1.4 Chemical structures of organic small-molecules 3

1.5 Chemical structures of organometallic small-molecules 4

1.6 Chemical structures of polymers 4

1.7 Chemical structures of iridium(III) complex polymer 5

1.8 Chemical structures of dendrimer (spiro-Cz) 5

1.9 Schematic of a single layer OLED setup 6

1.10 Energy level diagram of single layer OLED device architecture 7

1.11 Schematic of a multi-layer OLED setup 7

1.12 Energy level diagram of a multilayer OLED device architecture 8

1.13 Energy level diagram of a host-guest emitter layer OLEDs device 8

1.14 The CIE 1931 color space chromaticity diagram 9

1.15 The example graph of luminescence (cd/m2) vs. voltage (V) 10

1.16 Methods for detection amine drug: (a) CCR (b) CICA (c) GC-MS 11

2.1 Structure of homoleptic iridium(III) complexes 14

2.2 Structure of the cation iridium complexes 15

2.3 Structure of the cation iridium complexes C5, C6 and C7 15

2.4 Molecular structure of fac-Ir(SFP)3 and fac-(BFP)3 16

2.5 Structure of bis-cyclometalated iridium complexes from Chen and

et al.

16

2.6 (a) Molecular structure of the iridium complex C15 and C15-Pb2+

and (b) the absorption and emission spectra of (2.0x10-5

) upon

addition of increasing amounts of Pb2+

18

2.7

(a) The proposed mechanism of the sensing reaction and

(b) the emission spectra of C16 with various amounts of Hg2+

18

VIII

LIST OF FIGURES (CONTINUED)

FIGURE

PAGES

2.8 (a) The Molecular structure and (b) the phosphorescence

spectra of iridium (III) complex C17 (10 mM) upon addition

of different anions (10eq) in CH3CN

19

2.9 (a) Molecular structure and (b) Change in the UV absorption

spectra of Ir(TBT)2(acac) on addition of Hg2+

19

2.10 (a) Molecular structure and (b) UV-vis absorption spectra of

[Ir(Bpq)2(bpy)]PF6 in CH3CN solution with various amounts

of F-. Inset: solution color observed in a CH3CN solution

of [Ir(Bpq)2(bpy)]PF6 in the absence (left) and presence

(after) of 2 equiv. of F-

20

3.1 Experimental chart model of this work 25

3.2 Cleaning process for the patterned ITO glass 35

4.1 Synthetic method of A4 38

4.2 The mechanism of oxidation reaction 38

4.3 1H NMR in DMSO-D6 of A4 39

4.4 Synthetic method of L1 precursor 39

4.5 The mechanism of esterification reaction 39

4.6 1H NMR in CDCl3 of the L1 40

4.7 The synthetic route of dimethyl-2,2´bipyridine

4,4´dicarboxylate (L2)

40

4.8 The mechanism of oxidation reaction 41

4.9 1H NMR in DMSO-d6 of YN-13 41

4.10 1H NMR in CDCl3 of L2 42

4.11 The synthetic route to N3,N

3´-dibutyl-[2,2´-bipyridine]-

3,3´-dicarboxamide (L3)

42

4.12 The mechanism of oxalyl chloride reaction

43

4.13

1H NMR in CD3OD, FTIR and MS of N

3,N

3´-dibutyl-

[2,2´-bipyridine]-3,3´-dicarboxamide (L3)

43

IX


FIGURE

PAGES

4.14 Synthetic routines of the charged iridium(III) complexes

for OLEDs

45

4.15 1H NMR spectrum in CDCl3solution of KM01 46

4.16 1H NMR spectrum in CDCl3solution of KM02 46

4.17 (a) UVVis absorption spectra (b) Emission spectra of 1x10-5

M

KM01-KM04 in dichloromethane solution at room temperature

47

4.18 The picture of KM01-KM04 in dichloromethane solutions at

room temperature under normal light (left) and 356 nm UV

light (right)

48

4.19 Cyclic voltammograms of 1x10-3

M KM01-KM04 in dry

CH3CN with scan rate of 100 mV/s and 0.1 M TBAPF6 as

electrolyte

49

4.20 HOMO and LUMO distribution of the KM04 50

4.21 Structures of simple OLED devices 51

4.22 Current density and brightness versus applied bias voltage of

the device structure ITO/PEDOT:PSS/KM01-KM04:

BMIMPF6 (1:1)/TPBi/LiF/Al in acetronitrile

51

4.23 Schematics of energy level (eV) diagram of host-guest multi-

layer OLEDs using KM01-KM04 as emitter

53

4.24 CIE 1931 coordinates (x,y) and emission colour for OLED

devices of KM01-KM04 with configuration of ITO/ PEDOT:PSS/

Iridium complexes: BMIMPF6/TPBi/LiF/Al

53

4.25 Current density and brightness versus applied bias voltage of

the device structure ITO/PEDOT:PSS /KM04:BMIMPF6

(1:0.75)/TPBi/LiF/Al

54

4.26

Synthetic routines of the charged iridium(III) complexes for

sensor

55

X


FIGURE

PAGES

4.27 1H NMR spectrum in CDCl3 solution of NU02 55

4.28 UVVis absorption spectra of 2x10-5

M in CH3CN of the Ir(III)

complexes at room temperature

56

4.29 The visible absorption spectra of NU02 [2.5x10-2

M] and

n-BuNH2 in CH3CN solution with excess HCl at 5, 20, 60 and

120 min (right)

57

4.30 Changes in the absorption spectra of NU02 of 2.5x10-2

M and

with 1 equiv. n-BuNH2. Inset: the reaction picture at 0 and 120

min

57


M and

n-BuNH2 in CH3CN solution with (A) condition 3 (1 equiv HCl),

(B) condition 4 (10 equiv HCl) and (C) condition 5 (100 equiv

HCl). Inset: the reaction picture at 0 and 120 min

58


M and

n- BuNH2 in CH3CN solution with 100 equiv. HCl. Inset:

the reaction picture at 0 and 120 min

59


M and

with 10 equiv. HCl. Inset: the reaction picture at 0 and 120 min

59

4.34 UVVis absorption spectra of NU02 and KM10 of 2.5x10-2

M

in CH3CN at room temperature. Inset: The color picture of

NU02 and KM10

60

4.35 Changes in the absorption spectra of KM09 of 2.5x10-2

M and

100 equiv. HCl in CH3CN solution with 1 equiv.n-BuNH2.

Inset: The reaction picture at 0 and 120 min

61

XI


FIGURE

PAGES

A.1 13

C NMR in DMSO, ATR-FTIR (neat) and mass of A4

at room temperature

72

A.2 13

C NMR in CDCl3, ATR-FTIR (neat) of L1 at room temperature 73

A.3 13

C NMR in DMSO, ATR-FTIR (neat) and mass of YN-13

at room temperature

74

A.4 13

C NMR in CDCl3, ATR-FTIR (neat) and mass of L2 at room

temperature

75

A.5 13

C NMR in DMSO, ATR-FTIR (neat) and mass of L3 at room

temperature

76

A.6 ATR-FTIR (neat) and mass of KM05 at room temperature

77

A.7 ATR-FTIR (neat) and mass of KM06 at room temperature 78



A.10 ATR-FTIR (neat) and mass of NU02 at room temperature 81



A.13 13

C NMR in CDCl3, ATR-FTIR (neat) and mass of KM01

at room temperature

84

A.14 13

C NMR in CDCl3 and ATR-FTIR (neat) of KM02

at room temperature

85

A.15 13


at room temperature

86

A.16 13


at room temperature

87

XII

LIST OF ABBREVIATIONS

ABBREVIATION

FULL WORD

A Absorbance

AR. Analysis reagent

anh. Anhydrous

Aq. Aqueous

B Brightness

13C NMR Carbon nuclear magnetic resonance

cm

Centimeter

cm-1

Reciprocal centimeter (unit of wavenumber)

cm3 Centimeter cubic unit

δ Chemical shift in ppm relative to tetramethylsilane

CIE Commission Internationale de L’Eclairage or

International Commission on Illumination

conc. Concentrated

J Coupling constant (for NMR spectral data)

CE Current efficiency (cd/A)

CV Cyclic voltammetry

oC Degree Celsius

DI

Deionized Water

DFT Density functional theory

DCM Dichloromethane

DMSO Dimethyl sulfoxide

d Doublet (for NMR spectral data)

dd Double of doublet (for NMR spectral data)

ETL Electron transport layer

eV Electron volt

ESI-MS Electrospray ionization mass spectrometry

EML Emitting layer

XIII

LIST OF ABBREVIATIONS (CONTINUED)

ABBREVIATION

FULL WORD

Eg Energy gap

EtOAc Ethyl acetate

EQE External Quantum Efficiency

FTIR Fourier transform infrared spectroscopy

Hz Hertz

HOMO Highest occupied molecular orbital

HTL Hole transport layer

h Hour

ITO Indium-tin-oxide

LUMO Lowest unoccupied molecular orbital

IR Infrared

MS Mass spectroscopy

MHz Mega hertz

MLCT Metal to ligand charge transfer

mmol Milimole

mA Milli ampare

ml Milliliter

mmol Milimole

mV Millivolt

Min Minutes

Molar absorptivity

M Molarity

Mw Molecular weight

Mol Moles

m Multriplet (for NMR spectral data)

nm Nanometers

NMR Nuclear magnetic resocence

XIV

LIST OF ABBREVIATIONS (CONTINUED)

ABBREVIATION

FULL WORD

Ohm

OLED Organic light-emitting diode

Eox Oxidation potential

ppm Parts per million

ppy Phenylpyridine

PL Photoluminescence

PE Power efficiency (lm/W)

Ered Reduction potential

Rt Room temperature

s Singlet (for NMR spectral data)

m2 Square meter

TMS Tetra methylsilane

t Triplet (for NMR spectral data)

UV-Vis Ultra violet-visible

V Voltage

v/v Volume/volume

1

CHAPTER 1

INTRODUCTION

1.1 Importance in research and development

Heavy-metal complexes with phosphorescent emission are the important

luminescence materials [1-6], different from conventional fluorescent materials, which

are the triplet-state transition. Being among the best class of phosphorescent

heavy metal complexes, iridium(III) complexes are well known for their rich

photochemical and photophysical properties [7-9] due to their relatively short-excited

state lifetimes, high luminescence efficiencies [10], and excellent color tuning from blue

to the near-infrared region upon modification of the ligand [11,12] or by introducing

a variety of electron donors or acceptors into the ligand [13].

The iridium complex can be divided two structures namely the neutral iridium(III)

complexes and charged iridium(III) complexes.

Firstly, the neutral iridium(III) complexes, its structure compose of three

cyclometallating ligands (C^N), for example acetonylacetonate (acac), 2-phenylpyridine

(ppy) and difluorophenyl pyridine (dFppy) with anionic counter ion shown in Figure 1.1.

Figure 1.1 General structure of neutral iridium(III) complexes

2

Secondly, the charged iridium(III) complex, its structure compose of two C^N ligands

and a neutral N^N ligands such as bipyridine (bipy) and phenanthroline (phen) derivatives.

The charged iridium(III) complexes; (C^N)2Ir(N^N)PF6 are shown in Figure 1.2.

Figure 1.2 General structure of charge iridium(III) complexes

Phosphorescent light emitting materials have been used successfully in highly

efficient OLEDs [14,15] compared with fluorescent light emitting materials which

only singlet state excitons can emit the light. The phosphorescent light emitting

materials are efficient as both singlet and triplet excitons [16,17]. These complexes

have been explored for a multitude of photonic applications including organic

light-emitting diodes (OLEDs) [18,19] and biological labeling reagents [20].

Moreover, the iridium(III) complexes also have mainly focused on the new

chemosensors [14]. Moreover, the emission wavelength, lifetime and quantum

efficiency of this kind of phosphorescent material can be fine-tuned through

the modification of ligand structures and metal center.

1.2 Organic light emitting diodes (OLEDs) application

Prior to the OLEDs, display technology has been underwent a significant revolution.

The cathode ray tube (CRT), plasma display (PMD), liquid crystal display (LCD),

light emitting diode were used in the display market. All these displays have their own

limitations including bulkiness, low viewing angle, color purity, etc. The essential

requirements of next generation displays technology are reproduction of brightness,

3

pure color, high resolution, low weight, thin screen, reduction in cost and low power

consumption which are organic light-emitting diodes (OLED) display technology [21]

such as LG OLED TV, OLYMPUS STYLUS TG-2 and Dell Thunder shown in Figure 1.3.

55’’ OLED TV STYLUS TG-2 Dell Thunder

Figure 1.3 Examples of OLEDs displays in a market

1.2.1 Materials for OLEDs

OLED materials can be broadly classified as small (organic) molecules,

polymers and dendrimers.

Since the first report of multi-layered organic light-emitting diodes (OLEDs)

using small molecule by Tang and Van Slyke [22], Electroluminescence device

has been developed remarkably because they have used applications in full color flat panel

display [23-25]. They are semicrystalline or crystalline materials with high aqueous

solubility. The example of small organic material e.g. isrubrene, porphyrine, coumarin

and perylene are shown in Figure 1.4.

Figure 1.4 Chemical structures of organic small-molecules

4

In addition, several groups have reported the organometallic small molecules

composed of the metal centered atom and ligands as shown in Figure 1.5.

Figure 1.5 Chemical structures of organometallic small-molecules

The light emission color of the polymers strongly depends on the type of

the polymer, its chemical composition and the nature of side groups. Hence, by chemical

modification of the polymer structure, polymers can emit in ranging from 400 nm

to 800 nm. Another benefit of polymer is the incorporation with a small molecule

which influences the emission color of light-emitting polymers. By adding a small

amount of a suitable dye to a polymer, energy can be transferred from the polymer.

The color from the device can be tuned using different dyes. The example of organic

polymers as shown in Figure 1.6 and neutral iridium(III) complex polymer [26]

as shown in Figure 1.7.

Figure 1.6 Chemical structures of polymers

5

Figure 1.7 Chemical structures of iridium(III) complex polymer

Dendrimers generally consist of a central core, to which one or more

branched dendrons are attached. Surface groups attached to the distal end to provide

the solubility, which is necessary for solution processing. The dendritic structure

allows independent modification of the core (light emission), branching groups

(charge transport) and surface groups (processing properties). The example of spiro-Cz

dendrimer [27] is shown in Figure 1.8.

Figure 1.8 Chemical structures of dendrimer (spiro-Cz)

6

1.2.2 OLEDs structure and mechanism operation

In general, the basic OLED structure consists of a stack of emitting layers

sandwiched between a transparent conducting anode and metallic cathode.

After an appropriate bias is applied to the device, holes are injected from the anode

and electrons from the cathode. Then, the recombination events between the holes and

electrons result in electroluminescence (EL). This device called a single layer device;

however, there is sometimes difficulty in injecting carriers into the emitting layer.

To solve this problem, the structure was included with an electron transport layer

(ETL) and a hole transport layer (HTL) to balance charge and hole in the device.

This type called a multi-layer OLEDs device.

1.2.2.1 Single layer devices

Single layer architecture is the simplest OLED which is shown in

Figure 1.9. In this case the organic emitter is coated between the metal cathode and the

semiconductor anode. The organic emitter acts as an emitter and charge transport

material (holes and electrons) at the same time. The anode, indium-tin-oxide (ITO)

is used in most case. A thin semitransparent ITO layer is sputtered onto a glass

substrate. Afterwards, the emitting layer is deposited either by liquid phase

or evaporation techniques onto the ITO anode. Finally, metal cathode for example Al,

Ca and Mg is evaporated on top of the OLED substrate. A suitable cathode material

should a low work function in order to ensure efficient electron injection into

the organic semiconductor.

Figure 1.9 Schematic of a single layer OLED setup

After a voltage is applied to the electrode shown in Figure 1.9,

electrons from the cathode and holes from the anode are injected into the organic

semiconductor. Due to the electric field between the two electrodes, the positive and

7

negative charge carriers move through the organic emitting layer. As soon as they

recombine in the emitting material which called “exiton” and light is generated.

The energy level diagram of a single layer OLED is shown in Figure 1.10.

Figure 1.10 Energy level diagram of single layer OLED device architecture

1.2.2.2 Multi-layer devices

The OLED performance is determined by the number of charge

carriers that are injected the number of holes and electrons that actually recombine

under emission of light. The materials used in single layer devices are usually better

hole than electron conductors. As the holes are moving faster through the emitting

layer than electrons, the recombination zone shifted towards the cathode what usually

leads to a non-radiative loss of energy. Consequently, the efficiency decreases.

In order to improve device efficiency, the multi-layer architecture

was introduced as shown in Figure 1.11. The additional of the injection and transport

properties for holes and electrons should be similar to obtain a perfect charge carrier

balance which can improve the efficiency of the device. Therefore it is usually

necessary to use complex device architecture.

Figure 1.11 Schematic of a multi-layer OLED setup

8

In general working principles of multilayer shown in Figure 1.12,

a voltage is applied to the electrodes due to the electric field between the two electrodes.

The positive carriers move to the HTL and negative charge to ETL. The electrons and

holes are transfer into organic emitting layer. As soon as they recombine

in the emitting material which called “exiton” and light is generated [21].

Figure 1.12 Energy level diagram of a multilayer OLED device architecture

To improve a better performance and long term stability a modified

emitting layer was used called the host-guest system simplified in Figure 1.13.

The key parameter of this device is the energy matching of a host and a guest

especially in the emitting layer. The HOMO and LUMO levels of a host have a wider

energy band gap than the guest. Then the energy transfer can be progressed [21].

Figure 1.13 Energy level diagram of a host-guest emitter layer OLEDs device

9

1.2.3 Key parameters of the OLEDs

A key point in OLED development for full-color display application

is establishment of a set of red, green, and blue emitter (RGB) with higher

efficiencies, enhanced brightness, color purity and improved lifetime of optoelectronic

devices. Therefore, intensive research efforts in organic materials design and device

architectures are ongoing. The CIE chromaticity coordinates system as shown in

Figure 1.14 the method to define the chromaticity of a light source, will be used

throughout this thesis, since it is the preferred standard in the display and lighting

industries [28-31]. This method originally recommended in 1931 by the CIE defines

all metameric pairs by giving the amounta X, Y, Z of three imaginary primary colors

required by a standard observer to match the color being specified.

Figure 1.14 The CIE 1931 color space chromaticity diagram

The parameters for evaluation of the OLED performances in this work

are luminance, current efficiency, power efficiency and CIE coordinate. Therefore,

these terms and the others are described in this section.

1.2.3.1 Luminance (L)

In general, “brightness” is an expression of the amount of light

emitted from a surface per unit of area. It is called “luminance”, which is expressed as

candelas per square meter (cd/m2) of light emitting surface. For example, the luminance

of a incandescent light bulb is about 10,000 candelas per square meter. The luminous

intensity is defined as the emission in cd/m from the emitting surface therefore

the high luminous value means the device are much brighter as well.

10

1.2.3.2 Luminous efficiency (LE)

The luminous efficiencyof a source is a measure of the efficiency

which the source provides visible light from electricity. Luminous efficiency is measured

in candelas per ampere (cd/A). LE is calculated from this below equation [32-33].

Luminous efficiency =

Where L is the luminescence and j is the current density

(current/active area, mA/m2).

1.2.3.3 Luminous power efficiency (PE)

The luminous power efficiency is the amount of light emitted from

a source per voltage from electricity. Power efficiency is measured in lumens per watt

(lm/W). PE can be determined using the following equation [33]

Power efficiency =

Where L is the luminescence, j is the current density and V is the

applied voltage.

1.2.3.4 Turn on voltage

Turn on voltage is the begin brightness point at the low voltage in

OLEDs device. The graph plots between luminescence (cd/m2) vs. voltage (V) shown

in Figure 1.15.

Figure 1.15 The example graph of luminescence (cd/m2) vs. voltage (V)

Turn on voltage

11

1.3 Colorimetric sensor application

Phosphorescent heavy-metal complexes as a colorimetric sensor and biological

labeling reagent have attracted increasing interest due to their advantageous

photophysical properties.

The iridium(III) metal center can coordinate with various C^N cyclometalating

and N^N ligands to give a wide range of complexes with very interesting physical and

chemical properties. Some of these complexes have been utilized as a sensor for various

analytes, including metal cation, anions, pH and oxygen [34]. We anticipate that

this class of complexes can be developed as a new generation of colorimetric sensor

reagents because of their intense and high stability.

The organic amine bases such as amphetamine, methamphetamine and heroin are still

the problem of drug abuse. Structures of organic amine bases are shown below,

which is the primary amine, secondary amine and tertiary amine, respectively.

The methods for detection amine drugs can be divided into three methods called

chemical color reaction (CCR), color immunochromatographic assay (CICA) and

gas chromatography-mass spectrometry (GC-MS) according to the efficiency and

specificity. The three methods for detection amine drugs are shown in Figure 1.16.

(a) CCR (b) CICA (c) GC-MS

Figure 1.16 Methods for detection amine drug: (a) CCR (b) CICA (c) GC-MS

12

The first method has proved to be a convenient, simple and cheap. However,

this method has the less accuracy compared to the others. The second method is CICA,

the method has accurate than the CCR technique and confirm the results from the first

method. The third method, GC-MS has high accuracy and high specificity.

It has high costs and takes a long time for analysis compared to the others.

Additionally, a few types of phosphorescent iridium(III) complexes have been

reported as a amine CCR. It is well known that the photophysical properties of iridium(III)

complexes are dependent on the chemical structures of ancillary ligands [18]. When the

ancillary ligands of an iridium(III) complex contains a specific component to interact

with the analyte, the presence of this analyte leading to dramatic changes in

the photophysical properties of the iridium(III) complex.

1.4 Objectives of thesis

1.4.1 To synthesize N,N-bidentate ligands

1.4.2 To synthesize dimeric iridium complexes

13

1.4.3 To synthesize charged iridium(III) complexes

1.4.4 To characterize the molecular structure of the target complexes by 1H and

13C NMR, Fourier transforms infrared spectroscopy (FT-IR) and mass spectroscopy (MS)

1.4.5 To study the optical property of charged iridium complexes by UV-Visible

spectroscopy and fluorescence spectroscopy

1.4.6 To study the electrochemical property of charged iridium complexes (KM01,

KM02, KM03 and KM04) by cyclic voltammetry (CV)

1.4.7 To fabricate and investigate the OLEDs devices with KM01, KM02, KM03

and KM04

1.4.8 To study potential of our complexes for colorimetric n-butylamine sensor with

NU02, KM09 and KM10

CHAPTER 2

LITERATURE REVIEWS

2.1 Literature reviews

Organic light-emitting diodes (OLEDs) based on iridium (III) complexes is great

interest for application in display technology. Many research groups have been

intensive studied and designed of new materials leads to high efficiency, brightness,

lifetime and stable the color of optoelectronic.

In 1991, Watts and coworker [35] synthesized several substituted 2-phenylpyridine

which fac-Ir(ppy)3, C1, C2, and C3 for studying their photophysics. The parent

compound fac-Ir(ppy)3 shows a maximum emission wavelength at 494 nm, (77 K)

in ethanol/methanol (Figure 2.1). They focused that complex C1 with an electron

withdrawing group (F) exhibits 26 nm blue shift compared to fac-Ir(ppy)3.

In the opposite way, C3 with its electron donating group (OCH3) shows 45 nm red shift.

It is interesting to note the difference between the complex C2 and C3,

which is simply the effect of the position of the electron donating substitution on

the phenyl ring.

Figure 2.1 Structure of homoleptic iridium(III) complexes [35]

In 2010, Lei and coworker [36] synthesized the cationic iridium complex, Irdf-pyim

and Ir-pyim (Figure 2.2), in which cyclometalated 2-phenylpyridine and cyclometalated

2-(2,4-difluorophenyl) pyridine ligands. They tune light emission color from

blue green to red.

15

Figure 2.2 Structure of the cation iridium complexes [36]

The iridium (III) complexes such as C5, C6 and C7 [37] (Figure 2.3) were developed

by 4,5-diaza-9,9’-spirobifluorene as N^N ancillary ligands, in which one (C6) or two (C7)

phenyl groups. The photoluminescence of all the complexes exhibited maxima emission

in the range of 500 and 505 nm. The X-ray crystal structures of complexes C6 and C7

show that the pendant phenyl ring forms strong intramolecular face-to-face -stacking

with the difluorophenyl ring of the cyclometalated ligand with distances of 3.38 Å

for complex C6 and 3.46 Å for complex C7, respectively. The device characteristics

based on the structure of ITO/PEDOT:PSS/Complex C5 or C6 or C7/Al. They found that

the brightness can be increased to 10.6 cdm-2

with EQE value of 1.43% (for devices C7)

which explained by the minimization of -stacking interaction in the light-emitting

electrochemical call (LEC) devices.

Figure 2.3 Structure of the cation iridium complexes C5, C6 and C7 [37]

In 2010, Huang and coworkers [38] synthesized spiro-functionalized ligand

of the iridium complex fac-Ir(SFP)3 and fac-(BFP)3 which the steric hindrance

16

originates from the combination of rigid (Figure 2.4) and bulky three-dimensional (3D)

moieties. Devices were fabricated with a configuration of ITO/NPB (40 nm)/Ir(SFP)3

or Ir(BFP)3 doped CBP/BCP/Alq3 (10 nm)/LiF/Al. They found that the fac-Ir(SFP)3

exhibits impressive higher quantum yields at 10.0% more than alkyl-substituted

fac-(BFP)3 at 1.1%. The lower turn-on voltage and higher optimized dopant

concentration for fac-Ir(SFP)3 were observed. The phosphorescent organic

light-emitting diodes (PHOLEDs) exhibited a higher maximum brightness (Lmax) of

35,481 cd m-2

at 21.3 V, current efficiency of 44.3 cdA-1

, and power efficiency of

34.8 mW-1

. The both iridium complex display yellow-orange color with commission

international del'Eclairage (CIE) coordinates of (0.41, 0.56) and (0.42, 0.54), respectively.

Figure 2.4 Molecular structure of fac-Ir(SFP)3 and fac-(BFP)3

In addition bis-cyclometalated iridium(III) complexes based on structure of

spirobifluorene ligands were designed to iridium complexes (C11) (Figure 2.5).

Figure 2.5 Structure of bis-cyclometalated iridium complexes from Chen and

et al. [39]

17

The device configuration is ITO/PEDOT:PSS (50 nm)/PVK (50%):PBD (40%):

C11 (10%) (45 nm)/TPBi (40 nm)/LiF (0.5 nm)/Ca (20 nm)/Ag (150 nm).

The devices showed intense yellow emission in the range of 554 nm. Complex C11

achieved efficiency of 36.4 cd/A (10.1%) at 198 cd/m2 and maximum brightness

30,956 cd m-2

at 20 V.

From the previous literatures, OLEDs performance can be summarized in Table 2.1.

Table 2.1 Summary performance of device in OLEDs

Ir Complex Vturn-on

(V)

Bmax

(cd/m2)

CEmax

(cd/A)

PEmax

(lm/W)

CIE

(x, y)

Irdf-pyima

Ir-pyima

C5b

C6 b

C7 b

fac-Ir(SFP)3c

fac-Ir(BFP)3 c

C11d

6.9

4.0

-

-

-

3.7

5.2

5.8

890

11,500

25.4

5.76

10.6

35,481

20,196

30,956

0.6

4.1

2.13

3.37

4.25

44.3

24.2

36.4

-

-

1.9

3.1

3.9

34.8

11.1

-

0.21, 0.38

0.35, 0.56

0.23, 0.47

0.28, 0.50

0.28, 0.54

0.41, 0.56

0.42, 0.54

0.46, 0.52

a ITO/ PEDOT:PSS/PVK:OXD-7 or PBD:complexes/Cs2CO3/Al; OXD-7

for Irdfpyim and PBD for Ir-pyim [36]

b PEDOT:PSS/ITO/C5 or C6 or C7 with ionic liquid/Al [37]

c ITO/NPB/Ir(SFP)3 or Ir(BFP)3-doped CBP/BCP/Alq3/LiF/Al [38]

d ITO/PEDOT:PSS/PVK:PBD:C11/TPBI/LiF/Ca/Ag [39]

The photophysical properties of iridium(III) complexes are dependent

on the chemical structures of ancillary ligands. Which the ancillary ligand of an

iridium(III) complex contains a specific component to interact with the analyte,

the presence of this analyte can lead to dramatic changes in the photophysical properties

of the iridium(III) complex. Therefore, many research groups have been studied and

developed iridium (III) complexes to biological labeling reagents due to their high

luminescence quantum yields and long-lived excite.

18

Chi and coworkers [40] synthesized C15 which the iridium(III) bears two

cyclometalated and N-phenyl pyrazoles. They demonstrated the Pb2+

cation sensing

using the emissive spectra of C15 at room temperature. The phosphorescence upon

forming C15-Pb2+

can be confirmed by X-ray structural analyses as shown in Figure 2.6.

Figure 2.6 (a) Molecular structure of the iridium complex C15 and C15-Pb2+

and

(b) the absorption and emission spectra of (2.0 x 10-5

) upon addition of

increasing amounts of Pb2+

[40]

Lu and coworkers [41] synthesized a cyclometalated iridium complex,

Ir(dpci)2(dtc). It is called C16. The photoluminescence spectrum of C16 shows

maximum emission at 686 nm. C16 containing a dithiocarbamate ancillary ligand

can serve as a highly selective for Hg2+

. The emission spectra titration of C16 with

Hg2+

was also measured. It was found that the emission increases continuously until

the addition of 1 equiv. of Hg2+

(Figure 2.7). They explained by the elimination

of the dithiocarbamate ancillary ligand.

Figure 2.7 (a) The proposed mechanism of the sensing reaction and

(b) the emission spectra of C16 with various amounts of Hg2+

[41]

(a) (b)

(a) (b)

19

In 2014, Hyun and coworkers [42] synthesized C17 for phosphorescence

chemosensors for H2PO4-. The complex contained two preorganized urea groups

for the recognition of H2PO4- are shown in Figure 2.8.

Figure 2.8 (a) The Molecular structure and (b) the phosphorescence spectra

of iridium (III) complex C17 (10 mM) upon addition of different

anions (10eq) in CH3CN [42]

In 2012, Huang and coworker [43] synthesized a neutral iridium (III) complex

Ir(TBT)2(acac) based on 2-thiophen-2-yl-benzothiazole (TBTH) ligands containing

four sulfur atoms are shown in Figure 2.9 (left). Upon addition of Hg2+

to the solution,

the absorption band at 480 nm disappears progressively, while the absorption band

at 405 nm gradually increased. The color of the solution changed from orange to yellow,

in Figure 2.9 (right). The stoichiometry of Ir(TBT)2(acac) is given by the variation

of absorbance at 405 nm or absorbance 480 nm with respect to equivalents of added Hg2+

.

Figure 2.9 (a) Molecular structure and (b) Change in the UV absorption spectra

of Ir(TBT)2(acac) on addition of Hg2+

(a) (b)

(a) (b)

20

Huang and coworker [44] synthesized the iridium(III) complex [Ir(Bpq)2(bpy)]PF6

based on cyclometalated ligands (Bpq) containing a dimesitylboryl group.

Considering the significant response of ligand Bpq to F-, it is reasoned that

the photophysical and electrochemical properties of [Ir(Bpq)2(bpy)]PF6 could be

affected upon the addition of F-. The absorption shows the variation in the absorption

spectra of [Ir(Bpq)2(bpy)]PF6 upon the addition of F-. After F

- was added to a solution

of [Ir(Bpq)2(bpy)]PF6 the absorbance at 290 and 350 nm decreased gradually whereas

the absorbance at 400 nm increased, corresponding to an isobestic point at 379 nm.

Importantly, the absorption band in the range of 420-600 nm was red-shifted with

an increase in the absorbance, corresponding to a change in the solution color from

yellow to orange-red, in Figure 2.10 (inset), indicating that [Ir(Bpq)2(bpy)]PF6 can

serve as a “nakedeye” indicator of F-.

Figure 2.10 (a) Molecular structure and (b) UV-Vis absorption spectra of

[Ir(Bpq)2(bpy)]PF6 in CH3CN solution with various amounts of F

-.

Inset: solution color observed in a CH3CN solution of

[Ir(Bpq)2(bpy)]PF6 in the absence (left) and presence (after) of

2 equiv of F-

(a) (b)

CHAPTER 3

EXPERIMENTAL

3.1 Chemicals

All the chemicals used in this thesis are shown in Table 3.1 and Table 3.2

Table 3.1 Chemicals for the synthesis

Chemicals Formula Grade Manufacturer

Acetonitrile

n-Butylamine

Dichloromethane

Hydrochloric acid

Iridium(III) chloride hydrate

Methanol

4,4'dimethyl2,2´Bipyridine

Oxalyl chloride

1,10-Phenanthroline

Potassium hexafluorophosphate

Potassium hydroxide

Potassium permanganate

Pyridine

Sodium dichromate

Sodium hydroxide

Sodium sulfate

Sulfuric acid

Tetrahydrofuran (THF)

Toluene

CH3CN

C4H9NH2

CH2Cl2

HCl

IrCl3.xH2O

CH3OH

C12H12N2

(COCl2)2

C12H8N2

KPF6

KOH

KMnO4

C5H5N

Na2Cr2O7

NaOH

Na2SO4

H2SO4

C4H8O

C6H5CH3

ACS-for analysis

98%

ACS-for analysis

37%, for analysis

Hygroscopic

ACS-for analysis

99%

98%

ACS-for analysis

99%, extra pure

EKA pellets

AR

ACS-for analysis

99.5%

ACS- for analysis

ACS- for analysis

96% AR. Grade

ACS- for analysis

ACS- for analysis

CARLO ERBA

Fluka

CARLO ERBA

CARLO ERBA

Precious Metals

Online

CARLO ERBA

Acros organic

Acros organic

CARLO ERBA

Acros organic

CARLO ERBA

CARLO ERBA

CARLO ERBA

Aldrich

CARLO ERBA

CARLO ERBA

CARLO ERBA

CARLO ERBA

CARLO ERBA

22

Table 3.2 Chemicals for OLED devices

Chemicals Formula Grade Manufacturer

Acetone

Acetonitrile

Aluminum

1-Butyl-3-methylimidazolium

hexafluorophoaphate (BMIMP)

1,2-Dicholobenzene

Dichloromethane (DCM)

Ethanol

2-Propanol

Poly(methyl methacrylate)

Poly(3,4-ethylenedioxy-

thiophene)polystyrene

sulfonate

1,3,5-Tris(N-phenyl-

benzimidizol-2-yl)benzene

(TPBi)

Indium doped tin oxide (ITO)

glass 15Ω

CH3COCH3

CH3CN

Al

C8H15F6N2P

C6H5Cl2

CH2Cl2

CH3CH2OH

C3H7OH

(C5O2H8)n

C45H30N6

C14H11O5S2

-

ACS-for analysis

ACS-for analysis

Powder

98%

ACS-for analysis

ACS-for analysis

ACS-for analysis

ACS-for analysis

Premium Denture

Acrylic

Clevios P

VP.AI4083

99 %

Size 2.5x2.5 cm

CARLO ERBA

CARLO ERBA

Acros organic

Acros organic

CARLO ERBA

CARLO ERBA

CARLO ERBA

CARLO ERBA

LANG

H.C.Starck

Lumtec

Lumtec

http://en.wikipedia.org/wiki/Polystyrene_sulfonate

http://en.wikipedia.org/wiki/Polystyrene_sulfonate

http://en.wikipedia.org/wiki/Carbon

http://en.wikipedia.org/wiki/Oxygen

http://en.wikipedia.org/wiki/Hydrogen

23

3.2 Instruments and general chemical characterization techniques

3.2.1 Instruments for characterization

The general instruments used in the characterization are shown in Table 3.3

Table 3.3 Instruments for characterization technique

Instruments Model Company

Fourier Transform Infrared

Spectrometer (FT-IR)

UV-Visible Spectrometer (UV)

Nuclear Magnetic Resonance

(NMR)

Cyclic Voltammetry (CV)

Mass Spectroscopy (MS)

Melting point Apparatus (m.p.)

Fluorescence spectrometer

Ultrasonic cleaner

UVO cleaner

Spin-coater

Vacuum oven

Thermal evaporator

Luminance detector

Power supply and multimeter

Spectrum Two

V-650 spectrophotometer

Bruker ADVANCE,

300 MHz

AutolabMetrohm PG11

Micro TOF II

-

630

LS 50B

42-220

P6206

VD23

AUTO306

LS-110

2420

Perkin Elmer

Jasco

Perkin Elmer

Metro

Bruker

Buchi

Perkin-Elmer

Crest

Jelight

Specialty coating

systems

Binder

Edwards

Minolta

Keithley

3.2.2 General chemical characterization techniques

The chemical were used without further purification whereas dried solvent for

example toluene, pyridine and THF.

The structural of N,N-bidentate ligands, dimeric iridium(III) complexes and

charged iridium complexes were characterized by 1H,

13C NMR, melting point and FT-IR

techniques. The optical and electrical properties of the charge iridium(III) complexes were

characterized by UV-Visible spectroscopy and cyclic voltammetry, respectively.

24

3.2.2.1 Fourier Transform Infrared Spectroscopy (FT-IR)

Infrared (FT-IR) spectra were recorded with a Fourier transform

infrared spectrophotometer over the 4000 - 400 cm-1

range, at 16 nm/s scaning rate.

Data for FT-IR spectra are reported as follows: frequency (cm-1

).

3.2.2.2 UV-Visible spectroscopy

UV-Visible spectra were measured in a 1 cm path length quartz cell

using a V-650 spectrum high resolution UV-Vis for new charge iridium(III) complexes.

The samples were dissolved in dichloromethane, acetonitrile and diluted to

a concentration 2x10-5

M at room temperature.

3.2.2.3 Nuclear magnetic resonance (NMR)

1H and

13C NMR spectra were performed in CDCl3, DMSO-D6

or CD3OD recorded on 300 MHz spectrometer, using TMS as the internal reference.

Data for NMR spectra are reported as followed: chemical shift (δ ppm), multiplicity,

coupling constant (Hz) and integration (number).

3.2.2.4 Cyclic voltammetry (CV)

Cyclic voltammetry was conducted on a Metrohm PG11. The 1x10-3 M

solutions of the corresponding complexes were prepared in dichloromethane and

acetonitrile containing 0.1 M tetrabutylammoniumhexafluorophosphate ([Bu4N]PF6)

as supporting electrolyte, and purged with nitrogen gas for 60 min prior to use

at a scan rate of 100 mV/s at room temperature. The working electrode was a glassy

carbon electrode. The auxiliary electrode was a Pt electrode, and Ag/AgCl (3 M KCl)

electrode was used as reference electrode.

3.2.2.5 Mass spectroscopy

Molecular weight of charge iridium(III) complexes was measured

on Bruker, by Electrospray ionization Mass Spectroscopy (ESI-MS) techniques with

position mode.

3.2.2.6 Melting point apparatus (m.p.)

Melting points was measured on Buchi 530 scientific melting point

apparatus in open capillary method and are uncorrected and reported in degree

Celsius.

25

3.3 Experimental section

This experimental section part gives a summarized description of the synthesis

of the charge iridium(III) complexes for organic light-emitting diode (OLEDs)

and colorimetric n-butylamine sensor. It is divided in five main steps. First step is

the N^N ligand synthesis. Second step is the dimeric iridium complex synthesis.

Third step is the charge iridium(III) complex synthesis. Fourth to fifth steps are

the characterization and electrochemical studied and performance of OLEDs devices,

respectively. The overall experimental flow chart is shown in Figure 3.1.

Figure 3.1 Experimental chart model of this work

3.3.1 Synthesis of N^N ligand

3.3.1.1 The synthesis of dimethyl-2,2´-bipyridine-3,3´-dicarboxylate (L1)

Performance study of OLEDs

(KM01, KM02, KM03, KM04)

Application for amine sensor

(NU02, KM09, KM10)

Optical and electrochemical studies

Characterized by NMR, FT-IR, mass techniques

Charged iridium(III) complex synthesis

N^N ligand synthesis

(L1, L2 and L3)

Dimeric iridium complex synthesis

(KM05, KM06, KM07 and KM08)

26

1,10-Phenanthroline (1.00 g, 6 mmol) was dissolved in 75 ml of 0.12 M

potassium hydroxide and the mixture was heated to form a homogenous solution.

The 0.40 M aqueous potassium permanganate (40 ml) was slowly added to this

reaction mixture. The reaction was refluxed with stirring for 3 h. Then, the solid

was filtered to get an orange solution and cooled to room temperature followed by

extraction with dichloromethane (30 ml x 3). The aqueous layer was added with

conc. hydrochloric acid. After that, the crude product was evaporated to dryness to get

the product as 2,2'-bipyridine-3,3'-dicarboxylic acid (A4) (2.30 g, 97 %); m.p. 264 ºC

(decomposed); 1H NMR (300 MHz, DMSO-D6) δ 8.73 (d, J = 4.9 Hz, 2H), 8.35 (s, 2H),

7.67-7.54 (d, J = 4.8 Hz, 2H); 13

C NMR (75 MHz, ) δ 167.2, 158.6, 150.8, 138.6,

127.1, 123.5; ATR-FTIR (neat) 3397, 3071, 2573, 1726, 1623, 1395, 1220, 1065 cm-1

;

MS (ESI) m/z calcd for C12H8N2O4 (M-H+) 243.0406, found 243.0313.

The mixture of A4 (1.00 g, 4.1 mmol), 1 ml of conc. sulfuric acid

and 20 ml of methanol were refluxed for 24 h. The reaction mixture was cooled

to room temperature. Then the neutral solution was adjusted with sodium hydroxide

and extracted with dichloromethane (30 ml x 3). The organic layer was dried with

anhydrous sodium sulfate. The crude reaction was evaporated to dryness and

then passed through silica column chromatography using 5% MeOH:DCM to get

the target product L1 as colorless solid (0.49 g, 45 %); m.p.140 oC;

1H NMR

(300 MHz, CDCl3) δ 8.79 (dd, J = 4.9, 1.5 Hz, 2H), 8.40 (dd, J = 8.0, 1.5 Hz, 2H),

7.54 - 7.40 (dd, J = 8.0, 5.0 Hz, 2H), 3.70 (s, 6H); 13

C NMR (75 MHz, ) δ 165.9,

159.4, 151.5, 138.1, 125.3, 122.6, 52.2; ATR-FTIR (neat) 3004, 1711, 1599, 1412,

1296 and 1131 cm-1

; MS (ESI) m/z calcd for C14H12N2O4 (M+H+) 273.0875, found

273.0870.

3.3.1.2 The synthesis of dimethyl-2,2´bipyridine-4,4´dicarboxylate (L2)

Na2Cr2O7 (1.35g, 8.69 mmol) was added to 25 ml of conc. H2SO4

in 100 ml Erlenmeyer flask size. During the vigorous stirring, the reaction solution

27

was slowly added 4,4'dimethyl2,2'bipyridine (0.40 g, 2.17 mmol) and stirred for 30 min

(color changed from red to green). The reaction mixture was poured into ice water

(200 ml) and kept at 5oC for 1 h. The yellow precipitate was filtered, washed with

ice water (30 ml x 3) and dissolved with 10% NaOH. The initial pH was adjusted

to 2 by 10% HCl and filtered again. YN-13 was obtained as a white solid (0.22 g, 12 %);

m.p.> 260 oC;

1H NMR (300 MHz, DMSO-D6) δ 8.90 (d, J = 5.0 Hz, 2H), 8.82 (s, 2H),

7.90 (dd, J = 4.9, 1.5 Hz, 2H); 13

C NMR (75 MHz, DMSO-D6) δ 166.4, 156.0, 151.1, 140.0,

123.9, 120.0; ATR-FTIR (neat) 3112, 2437, 1706, 1603, 1458, 1285 and 1012 cm-1;

MS (ESI) m/z calcd for C12H8N2O4 (M-2H+) 243.0406, found 243.0450.

The mixture of YN-13 (0.22 g, 0.88 mmol), 1 ml of conc.sulfuric acid

and 20 ml of methanol were refluxed for 24 h. The reaction mixture was cooled to

room temperature. Then the neutral solution was adjusted with sodium hydroxide and

extracted with dichloromethane (30 ml x 3). The organic layer was dried with

anhydrous sodium sulfate. The crude reaction was evaporated to dryness obtained as

a solid (0.23 g, 94 %); m.p. 192 - 194 ºC; 1H NMR (300 MHz, CDCl3) δ 8.97 (s, 2H),

8.87 (d, J = 4.9 Hz, 2H), 7.91 (d, J = 4.9 Hz, 2H), 4.01 (s, 6H); 13

C NMR (75 MHz, CDCl3 )

δ 165.6, 156.5, 150.1, 138.6, 120.5, 52.7; ATR-FTIR (neat) 3000, 2920, 1727, 1589,

1433, 1290 and 1123 cm-1

; MS (ESI) m/z calcd for C14H12N2O4 (M+Na+) 295.0695,

found 295.0646.

3.3.1.3 The synthesis of N3,N



The mixture of 1 equiv. of A4 (1.00 g, 4.09 mmol) in dried toluene

was put in the round bottom flask, equipped with magnetic stirrer, nitrogen system

with a septum. Then, 3 equiv. of oxalyl chloride (1.75 ml, 20.0 mmol) were added

dropwise at room temperature. The mixture stirring was continued at room temperature

for overnight. Afterwards, the crude reaction was evaporated to dryness.

28

At 0 oC, dried THF (15 ml) was introduced to a stirred solution of

crude product. Then dried pyridine (1 equiv.) and dried n-butylamine (3 equiv.) were

added a suspension solution and left for 7 h at room temperature. And then water was

added. An aqueous solution of HCl was added (pH 5-7) and the mixture was stirred for

additional 10 min. The reaction mixture was extracted three times with DCM,

combined organic layers were washed with brine and dried over Na2SO4.

The organic solvent was removed in evaporator, to give crude product which was

purified by column chromatography on silica gel using 3% MeOH:DCM to get

the product L3 as brown-red solid (0.11 g, 8 %); 1H NMR (300 MHz, CD3OD)

δ 8.62 (dd, J = 4.9, 1.6 Hz, 2H), 8.05 (m, 2H), 7.56 (m, 2H), 4.90 (s, 2H),

3.20 (t, J = 6.8 Hz, 4H), 1.43 - 1.27 (m, 4H), 1.19 (ddd, J = 13.6, 8.7, 5.9 Hz, 4H), 0.88

(m, 6H); 13

C NMR (75 MHz, CD3OD) δ 168.8, 155.4, 149.2, 136.1, 132.5 - 132.2, 123.3,

39.0, 30.7, 19.6 - 19.3, 12.7; ATR-FIR (neat) 3252, 3069, 2957, 1631, 1579, 1411 and

1316 cm-1

; MS (ESI) m/z calcd for C22H28N2O2 (M+Na+) 377.1953, found 377.1687.

3.3.2 Synthesis dimeric iridium complex

The synthesis procedures of dimeric iridium complexes were reported

elsewhere [11]. In general synthesis is IrCl3.3H2O was combined with C^N ligand

for example; 2-phenylpyridine, dissolved in a mixture of 2-ethoxyethanol and DI water

before refluxing for 24 h. The solution was cooled to room temperature, and

the yellow precipitate was collected on a glass filter frit. The precipitate was washed

with ethanol and acetone to give a yellow solid of KM05

3.3.2.1 Tetrakis-(2-phenylpyridine-C2´,N)-(µ-dichloro) diiridium (KM05)

KM05 was obtained in 45 %; 1H NMR (300 MHz, acetone-D6)

δ 8.90 (d, J = 8.2 Hz, 2H), 8.51 - 8.32 (m, 4H), 8.23 (d, J = 8.1 Hz, 2H),

8.07 (dd, J = 8.2, 5.0 Hz, 2H), 7.96 - 7.82 (m, 4H), 7.67 (d, J = 5.5 Hz, 2H),

29

7.07 (t, J = 7.5 Hz, 2H), 7.01 - 6.89 (m, 4H), 6.45 (d, J = 7.4 Hz, 2H); 13

C NMR

(75 MHz, CDCl3) δ 155.5, 148.5, 146.9, 146.4, 137.4, 134.8, 127.0, 126.8, 124.9,

120.1, 118.6; ATR-FTIR (neat) 3039, 1603, 1476 and 1158 cm-1

; MS (ESI) m/z calcd

for C44H32Cl2Ir2N4 (M+) 1072.1263, found 1072.1036.

3.3.2.2 Tetrakis-(2-(thiophen-2´-yl)-pyridine-C5´,N)-(µ-dichloro)diiridium

(KM06)

KM06 was obtained in 35 %; 1H NMR (300 MHz, CDCl3)

δ 9.01 (d, J = 4.8 Hz, 1H), 7.62 (t, J = 7.5 Hz, 1H), 7.51 (d, J = 8.4 Hz, 1H),

7.09 - 7.03 (m, 1H), 6.62 (t, J = 6.4 Hz, 1H), 5.97 - 5.88 (m, 1H); 13

C NMR (75 MHz,

CDCl3) δ 165.0, 151.6, 149.9, 145.7, 136.7, 129.3, 127.6, 118.9, 117.0 ; ATR-FTIR

(neat) 3057, 1601, 1470 and 1152 cm-1

; MS (ESI) m/z calcd for C36H24Cl2Ir2N4S4 (M+)

1095.9519, found 1095.9364.

3.3.2.3 Tetrakis-(2-(2´,4´-difluorophenyl)-pyridine-C6´,N)-(µ-dichloro)

diiridium (KM07)

KM07 was obtained in 38 %; 1H NMR (300 MHz, CDCl3) δ 9.12

(d, J = 5.2 Hz, 1H), 8.31 (d, J = 8.4 Hz, 1H), 7.83 (t, J = 7.6 Hz, 1H), 6.83 (t, J = 6.2

Hz, 1H), 6.41 - 6.25 (m, 1H), 5.29 (dd, J = 9.1, 2.2 Hz, 1H); 13

C NMR (75 MHz,

CDCl3) δ165.3, 165.2, 164.2, 164.0, 162.2, 162.0, 160.8, 160.6, 158.7, 158.6, 151.3,

147.6, 147.5, 137.5, 127.8, 127.8, 127.7, 122.9, 122.5, 112.8, 112.7, 112.6, 112.5,

30

98.5, 98.1, 97.8; ATR-FTIR (neat) 3086, 1599, 1477, 1294, 1162 and 1112 cm-1

;

MS (ESI) m/z calcd for C44H24Cl2F8Ir2N4 (M+) 1231.0744, found 1239.0241.

3.3.2.4 Tetrakis-(1-(2´,4´-difluoro-phenyl)-1H-pyrazole-C6´,N

2)-

(µ-dichlo-ro) diiridium (KM08)

KM08 was obtained in 55 %; 1H NMR (300 MHz, CDCl3)

δ 8.43 (br, 1H), 7.75 (br, 1H), 7.23 (br, 2H), 6.68 (br, 1H), 6.57 - 6.31 (br, 1H), 5.36 (s, 1H);

ATR-FTIR (neat) 3086, 1613, 1480, 1257, 1107 and 1031 cm-1

; MS (ESI) : m/z calcd

for C37H23Cl2F8Ir2N8 (M+) 1190.0062, found 1195.0020.

3.3.3 Synthesis charged iridium(III) complex

3.3.3.1 [(dimethyl 2,2´-bipyridine-3,3´-dicarboxylate)-bis-(2-(phenyl)

pyridine-C2´,N)-iridium(III)] hexafluorophosphate (NU02)

KM05 (0.10 g, 0.10 mmol) and L1 (0.06 g, 0.22 mmol) was dissolved

in solution mixture of MeOH (10 ml) and DCM (10 ml). The reaction mixture was stirred

and refluxed at 45˚C under nitrogen for 24 h. After that, the red-orange solution was

cooled to room temperature then an excess of KPF6 (0.4 g, 2.17 mmol) was added.

The suspension was stirred for 1 h. then filtered by using sintered glass funnel.

The filtrate was removed organic solvent, and then crude product was purified by

column chromatography on silica gel using 5% MeOH:DCM to get the target product

31

as a red-orange solid (0.24 g, 93 %);1H NMR (300 MHz, CDCl3) δ 8.40 (s, 2H),

8.17 (s, 4H), 7.79 (d, J = 7.5 Hz, 2H), 7.67 (t, J = 7.7 Hz, 2H), 7.50 (d, J = 7.5 Hz, 2H),

7.49 (s, 2H), 7.08 (m, 4H), 6.96 (t, J = 7.3 Hz, 2H), 6.24 (d, J = 7.3 Hz, 2H), 3.87 (s, 6H);

13C NMR (75 MHz, CDCl3) δ 165.0, 155.9, 151.6, 149.1, 143.3, 139.4, 138.5, 133.1,

131.8, 131.0, 127.8, 124.8, 123.7, 123.0, 119.6, 113.9, 53.6; ATR-FTIR (neat) 3085,

2923, 1731, 1600, 1412, 1305 and 1296 cm-1

; MS (ESI) m/z calcd for C36H28IrN4O4

(M+-PF6)773.1740, found 773.1668.

3.3.3.2 [(dimethyl2,2´-bipyridine-4,4´-dicarboxylate)-bis-(2-(phenyl)

pyridine-C2´,N)-iridium(III)] hexafluorophosphate (KM09)

The synthesis procedure of KM09 is similar to NU02. KM05

(0.10 g, 0.11 mmol), L2 (0.06 g, 0.22 mmol) and KPF6 (0.4 g, 2.17 mmol) was used

in the reaction. After purification column chromatography on silica gel using 5%

MeOH:DCM. The KM09 was achieved (0.13 g, 64 %) as a red-orange solid; 1H NMR

(300 MHz, CDCl3) δ 9.06 (s, 2H), 8.12 (d, J = 5.5 Hz, 2H), 7.98 (d, J = 5.3 Hz, 2H),

7.90 (d, J = 8.1 Hz, 2H), 7.76 (t, J = 7.8 Hz, 2H), 7.69 (d, J = 7.6 Hz, 2H),

7.57 (d, J = 5.6 Hz, 2H), 7.07 (dd, J = 13.4, 6.7 Hz, 4H), 6.94 (t, J = 7.3 Hz, 2H),

6.28 (d, J = 7.4 Hz, 2H), 4.05 (s, 6H); ATR-FTIR (neat) 3043, 2921, 1729, 1607,

1478, 1261 and 1122 cm-1

; MS (ESI) m/z calcd for C36H28IrN4O4 (M+-PF6) 773.1740,

found 773.1644.

3.3.3.3 [(N3,N

3´-dibutyl-[2,2´-bipyridine]-3,3´-dicarboxamide)-bis-

(2-(phenylpyridine-C2’,N)-iridium(III)] hexafluorophosphate (KM10)

32


(0.17 g, 0.16 mmol), L3 (0.11 g, 0.32 mmol) and KPF6 (0.4 g, 2.17 mmol) was used in

the reaction. The product was purified by column chromatography by using

5% MeOH:DCM to give red-orange solid of KM10 (0.27 g, 86 %); 1H NMR

(300 MHz, CDCl3) δ 8.09 (d, J = 7.8 Hz, 1H), 7.98 (d, J = 5.3 Hz, 1H),

7.86 (d, J = 7.9 Hz, 1H), 7.72 (dd, J = 15.9, 7.9 Hz, 1H), 7.64 (d, J = 7.8 Hz, 1H),

7.37 - 7.25 (m, 1H), 7.06 (dd, J = 12.1, 5.0 Hz, 1H), 7.00 (t, J= 7.5 Hz, 1H),

6.94 - 6.75 (m, 2H), 6.23 (d, J = 7.5 Hz, 1H), 3.34 (dd, J = 13.3, 6.6 Hz, 2H),

1.58 (dt, J = 15.0, 6.6 Hz, 2H), 1.46 - 1.19 (m, 5H), 0.89 (dd, J = 15.6, 8.2 Hz, 4H);

13C NMR (75 MHz, CDCl3) δ 166.8, 164.9, 154.8, 150.4, 149.6, 147.8, 143.4, 138.1,

137.8, 131.8, 130.7, 127.2, 124.6, 123.5, 122.7, 119.4, 40.5, 31.0, 29.6, 20.1, 13.0;

ATR-FTIR (neat) 3428, 3063, 2923, 1661, 1607, 1529, 1478 and 1312 cm-1

;

MS (ESI) m/z calcd for C42H42IrN6O2 (M+-PF6) 855.2998, found 855.2889.

3.3.3.4 [(4,5-diaza-9,9´-spirobifluorene-N-N´)-bis-(2-phenylpyridine

C2´,N) iridium(III)] hexafluorophosphate (KM01)

The synthesis procedures of K1 were reported elsewhere [4] and

used in our work. K1 (0.20 g, 0.23 mmol) and KPF6 (0.4 g, 2.17 mmol) were dissolved

in solution mixture of MeOH (10 ml) and DCM (10 ml). The product was purified by


33

as a yellow solid (0.19 g, 87 %); 1H NMR (300 MHz, CDCl3): δ 7.95 (t, J = 6.5 Hz, 4H),

7.86 (t, J = 7.8 Hz, 4H), 7.79 - 7.64 (m, 4H), 7.46 (t, J = 7.5 Hz, 2H), 7.35 (d, J = 10.1 Hz, 4H),

7.32 - 7.19 (m, 4H), 7.04 (t, J = 7.4 Hz, 2H), 6.94 (t, J = 7.3 Hz, 2H), 6.70 (d, J = 7.5 Hz, 2H),

6.45 (d, J = 7.5 Hz, 2H);13

C NMR (75 MHz, ) δ 166.8, 161.8, 158.8, 149.4, 148.6,

144.2, 143.9, 143.7, 141.9, 141.5, 138.5, 134.6, 132.0, 130.6, 129.6, 128.8, 128.2,

124.4, 123.8, 123.8, 122.9, 120.8, 119.5; ATR-FTIR (neat) 3037, 1607, 1478 and

1163 cm-1

; MS (ESI) m/z calcd for C45H30IrN4 (M+-PF6) 819.2100, found 819.2100.

3.3.3.5 [(4,5-diaza-9,9´-spirobifluorene-N-N´)-bis-(2-thiophen-

2´-yl-pyridineC5´,N)-iridium(III)] hexafluorophosphate (KM02)


used in our work. K2 (0.19 g, 0.23 mmol) and KPF6 (0.4 g, 2.17 mmol) were used

in the reaction. The product was purified by column chromatography on silica gel

using 3% MeOH:DCM to get the target product as orange solid (0.16 g, 73 %);

1H NMR (300 MHz, CDCl3) δ 7.95 (dd, J = 13.9, 6.6 Hz, 2H), 7.85 (dd, J = 8.8, 6.7 Hz, 2H),

7.58 (m, 2H), 7.52 - 7.35 (m, 8H), 7.22 (m, 2H), 7.10 (dd, J = 15.0, 8.3 Hz, 2H),

6.67 (dd, J = 16.7, 7.8 Hz, 2H), 6.41 (d, J = 4.7 Hz, 2H); 13

C NMR (75 MHz, CDCl3)

δ 164.2, 161.9, 149.8, 149.0, 145.8, 143.6, 141.9, 141.3, 138.9, 136.9, 134.7, 130.6,

129.8, 129.6, 128.8, 128.3, 123.9, 121.0, 120.9, 120.9, 118.3; ATR-FTIR (neat) 2950,

1604, 1473 and 1157 cm-1

; MS (ESI) m/z calcd for C41H26IrN4S2 (M+-PF6) 831.1228,

found 831.1243.

3.3.3.6 [(4,5-diaza-9,9´-spirobifluorene -N-N´)-bis-(2-(2´,4´-difluorophenyl)

pyridine C6´,N)-iridium(III)] hexafluorophosphate (KM03)

34


used in our work. K3 (0.21 g, 0.23 mmol) and KPF6 (0.4 g, 2.17 mmol) were used

in the reaction. The product was purified by column chromatography on silica gel

using 3% MeOH:DCM to get the target product as yellow solid (0.16 g, 89 %);

1H NMR (300 MHz, CDCl3) δ 8.35 (d, J = 8.6 Hz, 1H), 7.98 - 7.82 (m, 3H),

7.78 (dd, J = 4.2, 1.5 Hz, 1H), 7.52 - 7.29 (m, 4H), 7.23 (dd, J = 13.9, 6.3 Hz, 1H),

6.70 (d, J = 7.6 Hz, 1H), 6.65 - 6.47 (m, 1H), 5.82 (dd, J = 8.3, 2.0 Hz, 1H);

ATR-FTIR (neat) 3087, 1602, 1478, 1248, 1165 and 1105 cm-1

; MS (ESI) m/z calcd

for C45H26F4IrN4 (M+-PF6) 891.1723, found 891.1766

3.3.3.7 [(4,5-diaza-9,9´-spirobifluorene -N-N´)-bis-(1(2´,4´difluorophenyl) -

1H-pyrazole-C6,N

2)-iridium(III)] hexafluorophosphate (KM04)


(0.10 g, 0.13 mmol), 4,5-diaza-9,9'-spirobifluorene (0.06 g, 0.19 mmol) and KPF6

(0.4 g, 2.17 mmol) were used in the reaction. The product was purified by


as a white solid (0.11 g, 85 %); 1H NMR (300 MHz, CDCl3) δ 8.42 (d, J = 2.6 Hz, 1H),

7.97 - 7.80 (m, 2H), 7.57 - 7.33 (m, 4H), 7.32 - 7.17 (m, 1 H), 6.83 - 6.63 (m, 3H),

35

5.86 (d, J = 7.6 Hz, 1H); ATR-FTIR (neat) 3166, 1615, 1416, 1258, 1108 and 1037 cm-1

;

MS (ESI) m/z calcd for C41H24F4IrN6 (M+-PF6) 869.1628, found 869.1676.

3.4 OLEDs device fabrication

The iridium complexes were prepared as previously described. A thin film of

electroluminescent material was sandwiched between two electrodes to fabricate

the devices. The devices were fabricated by solution processing, which is easily done

by spin-coating the solution on indium tin oxide (ITO) coated glass-substrates.

3.4.1 Cleaning process for the patterned ITO glass

The ITO glass was cleaned sequentially with a detergent in ultrasonic bath

at 40ºC for 10 min, deionized (DI) water for 5 min (two times), acetone for 5 min

(two times), 2-propanol for 5 min (two times) and hot vapor of ethanol at 225 ºC

for 10 min. Finally, the substrate was dried in vacuum oven at 100 ºC for 10 min and

led to UV ozone cleanser for 5 min. The cleaning step can be summarized in Figure 3.2.

Figure 3.2 Cleaning process for the patterned ITO glass

10 min

10 min

sonicated 5 min/ 2 times

sonicated 10 min

Deionized water

Acetone


2-Propanol

Hot vapor ethanol

Dried in vacuum oven at 100 ºC

Cleaned in UV ozone cleaner

Cleaned ITO glass


Detergent

36

3.4.2 Fabrication of OLEDs devices

After the ITO glasses were cleaned, the fabrication for OLEDs devices

as followed;

3.4.2.1 The coating PEDOT:PSS

First step, the ITO glass was covered by adhesive tape with four edges.

The top surface was blow out the dust by N2 gas. Second step, the PEDOT:PSS

(450 µl) was dropped onto a ITO glass placed on spin-coater and then spun

at 3000 rpm for 180 s. Finally, PEDOT:PSS film was baked at 260 ºC for 10 min and

keep in desiccators.

3.4.2.2 Spin coating emitting layer

In this thesis, we studied in two systems in the OLEDs which are

emitter in pure acetronitrile solvent and co-solvent as acetronitrile and

1,2-dichlorobenzene. Spin coating method for iridium (III) complexes (OLEDs),

KM01-KM04. The mixture of KM01-KM04 and BMIMP in acetonitrile 1:1 ratio

were filtered through PVDF membrane syringe (0.45 µm pore size), and then

the filtered solutions (350 µl) were spin-coated onto a patterned ITO glass coated with

the PEDOT:PSS film at 2500 rpm, 180 s. Then the ITO glass coated with the iridium (III)

complexes films were dried in vacuum oven at 60 °C for 30 min. In addition,

we studied to co-solvent as acetonitrile and 1,2-dichlorobenzene in similar procedure.

3.4.2.3 Electron transporting of organic deposition

The organic material in this work is TPBi was deposited after

the spin-coated. The assembly was transferred into a deposition chamber of

the thermal evaporator with a base pressure of 10-6

mbar for the deposition of

an organic material. The organic material was deposited on top of glass substrate by

evaporation at current of 10 A with evaporation rate of 1-3 Å/s.

3.4.2.4 Cathode electrode deposition

Finally, a thin LiF layer and Al cathode were sequentially

co-evaporated through a shadow mask with 5 mm wide slits arranged perpendicularly

to the 5 mm2fingers ITO, to obtain OLED with an active area. The operating vacuum

for evaporation of this cathode was under 10-6

mbar at high evaporation rate of

5-10 Å/s. The thickness of LiF and Al were 0.5 and 100 nm, respectively.

37

In order to investigate the performance of devices, standardize of

the measurement which the Luminance, current efficiency (cd/A), power efficiency

(lm/W), current density (mA/cm2) and CIE coordinate were performed with a I-L-V

Testing kiethley.

3.5 Colorimetric sensor study

The study of 2x10-2

M charge iridium(III) complexes (NU02 and KM09) in dried

acetonitrile for amine sensor were investigated by visible absorption in the range

of 400 - 800 nm. The reaction mixture was combined in beaker size 5 ml. Then,

the solution was stirred and heated at 60 ºC and measured the visible absorption

at 0 min, 5 min, 30 min, 60 min and 120 min. The number equivalents of acid were

varied including without HCl, 1 equiv. (0.1 M), 10 equiv. (1 M) and 100 equiv. (10 M)

of HCl. For study the equivalents of n-Butylamine, we studied with 1 equiv. (0.015 M)

and 3 equiv. (0.15 M) acid in dried acetonitrile.

38

CHAPTER 4

RESULTS AND DISSCUSSIONS

4.1 Synthesis of N^N ligand

4.1.1 The synthesis of dimethyl-2,2´-bipyridine-3,3´-dicarboxylate (L1)

The A4 was synthesized by reaction of the oxidation reaction

of 1,10-phenanthroline with potassium hydroxide and potassium permanganate to get

the resulting product as a white solid, 97% yield. The A4 was characterized by FT-IR

(appendix A) and NMR techniques, shown in Figure 4.1.

Figure 4.1 Synthetic method of A4

The mechanism of the oxidation reaction of 1,10-Phenanthroline shows in

Figure 4.2. The dimethyl on bipyridine derivative was converted into carboxylic acid

group, it was converted to A4 as white solid by KMnO4 and KOH.

Figure 4.2 The mechanism of oxidation reaction

A4 is a symmetric molecule as only 3 signals without carboxylic acid

proton. The 1H NMR spectrum of A4 in DMSO-D6 shows the signal at chemical shift

at δ 8.73 (2H), 8.35 (2H) and 7.67 - 7.54 (2H) assigned as proton of pyridine ring.

39

Figure 4.3 1H NMR in DMSO-D6 of A4

After that L1 was synthesized by reaction of the esterification reaction

of A4 with methanol and conc. sulfuric acid to get the resulting product as colorless

solid, 45% yield.

Figure 4.4 Synthetic method of L1 precursor

The mechanism of esterification reaction of L1 can be explained in Figure 4.5.

Figure 4.5 The mechanism of esterification reaction

40

The dicarboxylic acid on bipyridine derivative was converted into ester

group by the lone pair of oxygen in dicarboxylic acid was protonated with H2SO4

to give the carbocation. Then MeOH which nucleophillic attacks alcohol group on

bipyridine derivative and the elimination of H2O and H+ provided the target compound

as a white solid. The product was characterized by NMR in Figure 4.6 and FT-IR

(appendix A.1).

L1 is a symmetric molecule as only 4 signals of molecule was observed.

The 1H NMR spectrum of L1 shows the signal at δ 8.79 (2H), 8.40 (2H) and

7.54 - 7.40 (2H) ppm assigned as proton of pyridine ring. The chemical shift at 3.70

(6H) was assigned as the protons of the methyl group.

Figure 4.6 1H NMR in CDCl3 of the L1

4.1.2 The synthesis of dimethyl-2,2´bipyridine-4,4´dicarboxylate (L2)

The dimethyl-2,2'bipyridine-4,4'dicarboxylate (L2) ligand was synthesized

in two steps as shown in Figure 4.7. The intermediate (YN-13) was prepared oxidation

reaction by H2SO4/Na2Cr2O7 in 12% yield. Then, esterification reaction by methanol

and conc. sulfuric acid was used to get the target product (L2) in 94% yield.

Figure 4.7 The synthetic route of dimethyl-2,2´bipyridine-4,4´dicarboxylate (L2)

41

YN-13 ligand was synthesized by oxidation reaction of dimethyl on

bipyridine. It was oxidized by sodium dichromate (Na2Cr2O7) in acidic condition

to give aldehyde. Then, the resulting intermediate was further oxidized to carboxylic acid

to obtained as a white solid in 60% yield. The mechanism of the oxidation reaction

can be explained in Figure 4.8.

Figure 4.8 The mechanism of oxidation reaction

The characterization of YN-13 was investigated by 1H NMR,

FTIR and MS

(appendix A.3). The YN-13 is a symmetrical structure. The 1H NMR spectra shows

only 3 signals resonance chemical shift at 8.90 (2H), 8.82 (2H), and 7.90 (2H) ppm

assigned at as protons of aromatic pyridine ring as shown in Figure 4.9. The 13

C NMR

spectrum of YN-13 shows 5 carbon resonances for aromatic pyridine carbon and one

signal for carboxylic group (appendix A.3).

Figure 4.9 1H NMR in DMSO-D6 of YN-13

42

Then, the esterification of YN-13 with methanol and sulfuric acid was used

to synthesize the L2 ligand. The characterization of L2 was investigated by the

1H NMR,

FTIR and MS (appendix A.4).

The L2 is a symmetrical structure. The 1H NMR spectra only 4 signals

chemical shift at 8.97 ppm (2H), 8.87 (2H), and 7.91 (2H) assigned as protons

of aromatic pyridine ring and 4.01 ppm (6H) assigning as protons of ester functional

group as shown in Figure 4.10. The 13

C NMR spectra of L2 show 5 signals

for aromatic pyridine carbon and 1 signal for ester group (appendix A.4).

Figure 4.10 1

H NMR in CDCl3 of L2

4.1.3 The synthesis of N3,N

3´-dibutyl-[2,2´-bipyridine]-3,3´-dicarboxamide (L3)

L3 ligand was synthesized in two steps in Figure 4.11. A4 react with oxalyl

chloride to get the crude product. Then the amide group was formed by n-butylamine

to get the target product L3 in 8% yield.

Figure 4.11 The synthetic route to N3,N

3´-dibutyl-[2,2´-bipyridine]-3,3´-

dicarboxamide (L3)

The mechanism reaction shows in Figure 4.12. The dicarboxylic acid

on bipyridine derivative was converted to acid chloride, then it was converted

43

to N3,N

3´-dibutyl-[2,2´-bipyridine]-3,3´-dicarboxamide (L3) as orange solid by

pyridine, THF and n-butylamine.

Figure 4.12 The mechanism of oxalyl chloride reaction

The characterization of L3 was investigated by the 1H NMR,

FTIR and MS

as shown in Figure 4.13.

4000 3500 3000 2500 2000 1500 1000 50030

40

50

60

70

80

90

100

110

% Tra

nsmitta

nce

Wavenumber (cm-1)

Figure 4.13 1H NMR in CD3OD and FTIR of N

3,N



44

The L3 is a symmetrical structure. The 1H NMR spectra shows 8 signals

chemical shift at 8.62 (2H), 8.05(2H), and 7.56(2H) ppm assigned as protons

of aromatic pyridine ring, δ 4.90 (2H) assigned as protons amide, 3.20 (4H),

1.43 - 1.27 (4H), 1.19 (4H) and 0.88 (6H) ppm assigned as protons of butyl group

in amide group. The 13

C NMR spectra of L3 show 5 signals for aromatic pyridine

carbon and 5 signals for amide group (appendix A.5).

4.2 The charged iridium(III) complex

Generally, the first step is the synthesis of dinuclear cyclometalatediridium(III)

chlorobridged by the refluxing with C^N ligand and iridium(III) chloride hydrate

in 2-ethoxyethanol for 24 h. is shown below.

The second step is the synthesis of charged iridium(III) complexes by refluxing

with N^N bidentate ligand and KPF6 in MeOH and DCM for 24 h. KM01-KM03 were

synthesis in some second step as KPF6. Whereas KM04 synthesis in all second step.

4.2.1 The charged iridium(III) complexes for OLEDs

The charged iridium(III) complexes were successfully formed as showed

in Figure 4.14.

4.2.1.1 Synthesis iridium(III) complexes and characterization

45

Figure 4.14 Synthetic routines of the charged iridium(III) complexes for OLEDs

KM01 is a symmetric molecule as only 15 proton signals of one ppy

and spiro ligands were observed at chemical shift 7.95 - 6.45 ppm as shown in Figure 4.15.

The signals at chemical shift 7.95 (4H), 7.86 (4H), 7.79 - 7.64 (4H) and 7.46 (2H) ppm

were assigned to fourteen protons of the spiro ligand. The signal chemical shift

at 7.35 (4H), 7.32 - 7.19 (4H), 7.04 (2H), 6.94 (2H), 6.70 (2H) and 6.45 (2H) ppm

were assigned to protons of phenyl pyridine ring ligand. Mass spectrum of the complex

at 819.2100 (m/z) was assigned to M+-PF6 (appendix A.13).

46

Figure 4.15 1H NMR spectrum in CDCl3 solution of KM01

KM02 is a symmetric molecule as only 13 proton signals

of thiophenyl pyridine and spiro ligands were observed at chemical shift 7.85 - 6.41 (26H)

ppm as shown in Figure 4.16.

Figure 4.16 1

H NMR spectrum in CDCl3solution of KM02

It was found that the signals at chemical shift 7.95 (2H), 7.85 (2H),

7.72 (4H), 7.58 (2H), 7.52 - 7.35 (8H), 7.22 (2H), 7.10 (2H), 6.67 (2H) and 6.41 (2H) ppm

assigned to 26 aromatic protons of pyridine and spiro ligands. Mass spectrum

of the complex at 831.1243 (m/z) is assigned to M+-PF6 (appendix A.14).

Similarly, KM03 also is a symmetric molecule as only 13 proton

signals of difluorophenyl pyridine and spiro ligands. Mass spectrum of the complex

showed the peaks at 891.1766 (m/z) is assigned to M+-PF6 (appendix A.15).

47

KM04 shows a symmetric molecule of difluorophenyl pyrazole

and spiro ligands at chemical shift 8.35-5.82 ppm. Mass spectrum of the complex

at 869.1676 (m/z) is assigned to M+-PF6 (appendix A.16).

4.2.1.2 The photophysical properties

The UV-Vis absorption spectra of KM01-KM04 in dichloromethane

solutions at room temperature are shown in Figure 4.17 (a). The complexes exhibit

main absorption bands below 300 nm region, due to spin-allowed * transition

in ligand-centered (LC) transition of the C^N cyclometalated ligand and N^N ligand.

The weak absorption bands shows at 330 - 450 nm corresponding to metal-to-ligand

charge transfer (MLCT) transition, respectively.

250 300 350 400 450 500 550 600

0.0

0.2

0.4

0.6

0.8

1.0

KM01

KM02

KM03

KM04

No

rm

ali

zed

Ab

sorp

ba

nce I

nte

nsi

ty (

a.u

.)

Wavelength (nm)

450 500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0 KM01

KM02

KM03

KM04

No

rm

ali

zed

PL

In

ten

sity

(a

.u.)

Wavelength (nm)

Figure 4.17 (a) UVVis absorption spectra (b) Emission spectra of 1x10-5

M

KM01-KM04 in dichloromethane solution at room temperature

The emission spectra of KM01-KM04 in dichloromethane solutions

at room temperature are shown in Figure 4.17 (b). The maximum emission

wavelengths of KM01-KM04 are 550, 586, 505 and 488 nm, respectively.

(b)

(a)

48

These complexes generated color as yellow, orange, green and blue. From the results,

the maximum emission wavelength of KM02 shows red-shifted compared KM01

because of electron donating groups (thiophenyl pyridine). In the another hand,

KM03 and KM04 show blue-shifted compared KM01 because of electron

withdrawing groups (fluorine atoms). The emission quantum yield about 0.01 - 0.07

was obtained by using a solution of quinine sulfate served as the standard under

air condition. The emission spectra of a cationic cyclometalated iridium(III)

complexes in solution were successfully tuned from green to red. The photophysical

characteristics of these complexes are summarized in Table 4.1.

Table 4.1 Photophysical characteristics of KM01-KM04 solution

Complex

Solution

abs a

(nm, log )

ex

(nm)

em

(nm) PL

b

KM01

KM02

KM03

KM04

269 (4.7), 305 (4.3), 418 (3.7)

274 (4.7) 319 (4.4), 424 (3.9)

264 (4.7), 316 (4.3), 429 (3.1)

256 (4.7), 319 (4.1), 416 (3.4)

305

319

316

319

550

586

505

488

0.014

0.003

0.054

0.078

a in dichloromethane solution (2x10

-5 M)

b Determined in dichloromethane solutions (A < 0.1) at room temperature using quinine

sulfate solution in 0.01 M H2SO4 as a standard under air condition

Figure 4.18 The picture of KM01-KM04 in dichloromethane solutions at room

temperature under normal light (left) and 356 nm UV light (right)

49

4.2.1.3 Electrochemical properties

The electrochemical properties of KM01-KM04 were investigated

by cyclic voltammetry (Figure 4.19) and the redox potentials are summarized

in Table 4.2. The cyclic voltammogram was studied with Ir(III) complexes

in a 1x10-3

M (dry CH3CN) containing 0.1 M tetrabutylammoniumhexafluorophosphate

(TBAPF6) and working electrode with a glassy carbon (GC). Ferrocene was used

as the standard for a monoelectronic chemically and electrochemically reversible

reaction.

Figure 4.19 Cyclic voltammograms of 1x10-3

M KM01-KM04 in dry CH3CN with

scan rate of 100 mV/s and 0.1 M TBAPF6 as electrolyte

In addition, the HOMO and LUMO energy levels of those iridium

complexes were estimated according to the electrochemical and photophysical

absorption. The energy gap (Eg) were estimated according to onset of absorption

spectra (Eg = 1240/onset). The HOMO and LUMO energy levels were calculated from

equation; HOMO = -e(Eox + 4.8 eV - Eox(ferocene)) and LUMO = HOMO + Eg [45].

The electrochemical properties of KM01-KM04 are summarized in Table 4.2.

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

-80

-60

-40

-20

0

20

40

KM01

KM02

KM03

KM04

Ferrocene

Cu

rren

t (m

A)

Potential (V)

50

Table 4.2 Electrochemical properties and energy levels of KM01-KM04

Complex Eoxa (V) onset

b Eg

c (eV) HOMO

d (eV) LUMO

e (eV)

KM01

KM02

KM03

KM04

1.33

1.23

1.66

1.72

491

510

451

419

2.53

2.43

2.75

2.96

-5.69

-5.59

-6.02

-6.08

-3.16

-3.16

-3.27

-3.12

a Measured in CH3CN solution containing 0.1 M n-Bu4NPF6 as a supporting

electrolyte at a scan rate of 100 mV/s

b Estimated from the absorption spectra

c Estimated from the onset of the absorption spectra (Eg = 1240/onset)

d Calculated from HOMO = - e(Eox + 4.8eV - Eox(ferocene)) where Eox(ferocene) = 0.44 V

e Calculated from equation LUMO = HOMO + Eg

As shown in Table 4.2, the oxidation potentials of KM01-KM04

were observed at 1.33, 1.23, 1.66 and 1.72 V, respectively, attributed to the oxidation

of Ir(III) to Ir(IV) [52]. Compared with KM03 and KM04, the energy gap of KM01

showed a high value which can be explained the electron withdrawing group on ligand

of KM03 and KM04. In another hand, KM02 showed a low energy gap at 2.43 eV

due to electron rich thiophenylpyridine ligand.

The results were supported by the DFT calculations. Specifically

of KM04, the HOMO is distributed between the Ir atom and the benzene rings of the

difluorophenylpyrazole ligand and LUMO are mainly located on the bipyridine rings

are shown in Figure 4.20.

Figure 4.20 HOMO and LUMO distribution of the KM04

HOMO LUMO

51

4.2.1.4 Electroluminescence study.

The electroluminescence of the KM01-KM04 was investigated

with a multi-layer OLED by using host-guest technique, in Figure 4.21

Figure 4.21 Structures of simple OLED devices.

The figure showed the configuration of the devices which

PEDOT:PSS was used as a hole-injecting layer. The KM01-KM04 were used as the

emitter with ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6)

with a pure acetonitrile to provide additional PF6- anions. 1,3,5-tris(N-phenyl-

benzimidizol-2-yl)benzene (TPBi), electron transporting layer, was placed between

cathode and emitting layer for reduce the energy barrier in the injection of electron

from cathode to emitting layer [46]. The J-V-L characteristics of multi-layer OLED

devices are shown in Figure 4.22.

Figure 4.22 Current density and brightness versus applied bias voltage of the

device structure ITO/PEDOT:PSS/KM01-KM04:BMIMPF6

(1:1)/TPBi/LiF/Al in acetronitrile

0 2 4 6 8 10 12

0

40

80

120

160

200

240 KM01

KM02

KM03

KM04

Voltage (V)

Cu

rren

t d

ensi

ty (m

A/c

m2

)

1

10

100

1000

Bri

gh

tnes

s (cd

/m2

)

52

The maximum brightness at 2027, 103, 879 and 27cd/m2 and

the maximum current efficiency at 1.72, 0.07, 1.68 and 0.19 cd/A can be observed

with KM01-KM04, respectively. We found that KM01 gave high brightness

to 2027 cd/m2 compared others. The KM01 show that a maximum current efficiency

at 1.72 cd/A, the brightness 2027 cd/m2 at 10 V and CIE coordinate (x,y) of 0.48, 0.50.

can be observed. The characteristics of multi-layer OLED devices of KM01-KM04

are summarized in Table 4.2.

Table 4.3 Summary of host-guest multi-layer OLED performances with configurations

of ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1)/TPBi/LiF/Al

Complex Vturn-on

a

(V)

Bmaxb

(cd/m2)

CEmaxc

(cd/A)

PEmaxd

(lm/W)

CIEe

(x, y)

KM01

KM02

KM03

KM04

4.7

5.7

5.3

4.9

2027

130

879

27

1.72

0.07

1.68

0.19

0.77

0.27

0.70

0.10

0.48, 0.50

0.56, 0.42

0.29, 0.53

0.24, 0.43

aThe voltage at luminance of 1 cd/m

2

b Maximum brightness

c Current density at maximum luminance

d Power efficiency at maximum luminance

e CIE coordinates

The results showed that KM04 gave a low brightness and current

efficiency. The result can be explained by the energy profile (Figure 4.23).

The HOMO level of KM04 was observed at -6.08 eV which is not suitable with

HOMO level of PEDOT:PSS at -5.3 eV (Figure 4.23). Moreover, we found that

the KM04 gave a low solubity in pure acetronitrile. This observation could also be

a responsible for a low performance.

53

Figure 4.23 Schematics of energy level (eV) diagram of host-guest multi-layer

OLEDs using KM01-KM04 as emitter

The CIE coordinates and their emission color for OLED devices of

KM01-KM04 are shown in Figure 4.24.

Figure 4.24 CIE 1931 coordinates (x,y) and emission colour for OLED devices

of KM01-KM04 with configuration of ITO/PEDOT:PSS/Iridium

complexes:BMIMPF6/TPBi/LiF/Al

We found that, the charged complexes successfully generated

emission color from yellow, orange, green and blue with related the color under

UV light (Figure 4.18). This color is according to energy gap (Table 4.2). KM04 is

high energy band gap more other complexes as a result green. While KM02 is small

energy band gap when compared KM01, KM03 and KM04.

54

To improve a better performance, KM04 was studied with

a co-solvent as acetonitrile and 1,2 dichlorobenzene (1:1 v/v) and modified ratio of ionic

liquid to (1:0.75). The J-V-L characteristics are shown in Figure 4.26.

0 2 4 6 8 10 12

0

100

200

300

400

500

600

700

KM04

Voltage (V)

Cu

rren

t d

ensi

ty (m

A/c

m2

)

0.1

1

10

100

1000

Bri

gh

tnes

s (c

d/m

2)

Figure 4.25 Current density and brightness versus applied bias voltage of the

device structure ITO/PEDOT:PSS/KM04:BMIMPF6 (1:0.75)/

TPBi/LiF/Al

From the result, the better brightness at 212 cd/m2

and current

efficiency at 0.29 cd/A can be obtained which the modified system affected to smooth

film on ITO glass compared with pure acetronitrile. The performances are summarized

in Table 4.4.

Table 4.4 Summary of host-guest OLED device performances with configurations

of ITO/PEDOT:PSS/KM04:BMiMPF6(1:0.75)/TPBi/LiF/Al

Complex Vturn-on

a

(V)

Bmaxb

(cd/m2)

CEmaxc

(cd/A)

PEmaxd

(lm/W)

CIEe

(x, y)

KM04 5.1 212 0.29 0.13 0.22, 0.38

aThe voltage at luminance of 1 cd/m

2

b Maximum brightness

c Current density at maximum luminance

d Power efficiency at maximum luminance

e CIE coordinates

55

4.2.2 The charged iridium(III) complexes for chemical sensor application

The complexes were designed with active functional group (ester) in neutral

ligand as shown in structure of NU02 and KM09. The general synthesis was used

in two steps similar as OLEDs.

4.2.2.1 Synthesis iridium(III) complexes and characterization

Figure 4.26 Synthetic routines of the charged iridium(III) complexes for sensor

NU02 is a symmetric molecule as only 14 proton signals of one

ppy and bipyridine dicarboxylate ligands were observed at chemical shift 8.39 - 3.87

ppm as shown in Figure 4.32.

Figure 4.27 1H NMR spectrum in CDCl3 solution of NU02

56

The 1H NMR spectra of NU02 showed the signals at chemical shift

3.87 (6H) ppm assigned to six protons of the bipyridine dicarboxylateligand. The signals

at chemical shift 8.40 (2H), 8.17 (4H), 7.91 (2H), 7.79 (2H), 7.67 (2H), 7.50 (2H),

7.08 (4H), 6.96 (2H) and 6.24 (2H) ppm were assigned to 28 aromatic protons of pyridine

and ester ligands. Mass spectrum of the complex at 773.1668 (m/z) is assigned to M+-PF6

(appendix A.10).

KM09 is a symmetric molecule as only 14 proton signals of one ppy

and bipyridine dicarboxylate ligands were observed at chemical shift 9.06-4.05 ppm

(appendix A.11). The signal at chemical shift 4.05 (6H) ppm were assigned to six protons

of the bipyridine dicarboxylateligand. The signals at chemical shift 9.06 (2H), 8.12 (2H),

7.98 (2H), 7.90 (2H), 7.76 (2H), 7.69 (2H), 7.57 (2H), 7.07 (4H), 6.94 (2H) and

6.28 (2H) ppm were assigned to 28 aromatic protons of pyridine and ester ligands.

Mass spectrum of the complex showed the peaks at 773.1644 (m/z) assigned to M+-PF6

(appendix A.11).

4.2.2.2 The Photophysical properties

The UV-Vis absorption spectra of NU02 and KM09 in acetonitrile

solutions at room temperature are shown in Figure 4.28. The UV-visible absorption

spectra of the complex display a similar peak at reported in KM01-KM04 from LC and

MLCT transition, respectively. The absorbance of NU02 and KM09 found that covered

both UV-Visible range (240-500 nm). However, for the application in CCR technique,

we studied the changing colors in the visible range as shown in Figure 4.29 - 4.35.

250 300 350 400 450 500

0.0

0.2

0.4

0.6

0.8

1.0 NU02

KM09

No

rma

lize

d A

bso

rba

nce

In

ten

sity

(a

.u.)

Wavelength (nm)

Figure 4.28 UVVis absorption spectra of 2x10-5

M in CH3CN of the Ir(III)

complexes at room temperature

57

4.2.2.3 Study of iridium(III) complexes for colorimetric n-butylamine

sensor application in various conditions

Firstly, the chemical sensor was investigated by NU02 with

3 eq. n-BuNH2 in the three drop of conc. HCl condition (excess). This reaction was

monitored in Figure 4.30. Upon addition of reaction time, the absorption bands show

dramatically change to a blue shifted from 536 to 474 nm within 2 hour.

Condition 1: 1 eq. NU-02: 3 eq. n- BuNH2: conc HCl (excess)

450 500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

No

rm

ali

zed

Ab

sorb

an

ce I

nte

nsi

ty (

a.u

.)

Wavelength (nm)

NU02

5 min

30 min

60 min

120 min

Figure 4.29 The Visible absorption spectra of NU02 [2.5x10-2

M] and n-BuNH2

in CH3CN solution with excess HCl at 5, 20, 60 and 120 min

Then, we studied the number equivalent of acid and n-BuNH2

in 4 conditions include without HCl as shown in Figure 4.30.

Condition 2: 1 eq. NU-02 [2.5x10-2 M: 1 eq. n- BuNH2 without HCl

500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

0 min

5 min

30 min

60 min

120 min

Norm

ali

zed

Ab

sorb

an

ce I

nte

nsi

ty (

a.u

.)

Wavelength (nm)

Figure 4.30 Changes in the absorption spectra of NU02 of 2.5x10-2

M and with

1 equiv. n-BuNH2. Inset: the reaction picture at 0 and 120 min

0 min 120 min

58

Then, we varied the number equivalent of acid in 3 conditions

including 1 equiv, 10 equiv and 100 equiv as shown in Figure 4.31.

Condition 3: 1 eq. NU-02 [2.5x10-2 M]: 3 eq. n- BuNH2: 1 eq. HCl

Condition 4: 1 eq. NU-02 [2.5x10-2 M :3 eq. n- BuNH2: 10 eq. HCl

Condition 5: 1 eq. NU-02 [2.5x10-2 M]: 3 eq. n- BuNH2: 100 eq. HCl

500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d A

bso

rba

nce

In

ten

sity

(a

.u.)

Wavelength (nm)

0 min

5 min

30 min

60 min

120 min

500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d A

bso

rba

nce

In

ten

sity

(a

.u.)

Wavelength (nm)

0 min

5 min

20 min

60 min

120 min

450 500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d A

bso

rba

nce

In

ten

sity

(a

.u.)

Wavelength (nm)

0 min

5 min

30 min

60 min

120 min


M and n-BuNH2

in CH3CN solution with (A) condition 3 (1 equiv HCl), (B) condition 4

(10 equiv HCl) and (C) condition 5 (100 equiv HCl). Inset: the reaction

picture at 0 and 120 min

(A)

(B)

(C)

0 min 120 min

0 min 120 min

0 min 120 min

59

Upon the addition of equivalent of HCl to the solution of NU02 and

butylamine, these results suggested that the 100 equiv. HCl gave a fast reaction with

more than 50 nm change from 528 to 450 nm. Hence, we conclude that NU02 can be

used as a colorimetric sensor toward n-BuNH2. Afterwards, we studied an equivalent of

n-BuNH2 with 100 eq. HCl as shown in Figure 4.32. The data shows the shifted maxima

absorption similar as 3 eq. of n-BuNH2.

Condition 6: 1 eq. NU-02 [2.5x10-2 M: 1 eq. n- BuNH2: 100 eq. HCl

450 500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0 0 min

5 min

30 min

60 min

120 min

Nor

mal

ized

Ab

sorb

ance

In

ten

sity

(a.

u)

Wavelength (nm)


M and n- BuNH2

in CH3CN solution with 100 equiv. HCl. Inset: the reaction picture

at 0 and 120 min

Then, we proved that reaction need n-BuNH2 to form a new

chromophore by using condition 7. The results conclude that a new chromophore doesn’t

observe with this condition (Figure 4.33).

Condition 7: 1 eq. NU-02 [2.5x10-2 M]: 100 eq. HCl withoutn n- BuNH2

500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

0 min

5 min

30 min

90 min

120 min

Nor

mal

ized

Ab

sorb

ance

In

ten

sity

(a.

u.)

Wavelength (nm)


M and with

10 equiv. HCl. Inset: the reaction picture at 0 and 120 min

0 min 120 min

0 min 120 min

60

In addition, the changed absorption spectra suggested a formation

of new chromophore in the complex. The amide formation could be a responsible from

the ester functionalize moieties and amine analyze. Therefore, we synthesized and

studied the absorption the amide complex (KM10) as shown in Figure 4.34.

Figure 4.34 UVVis absorption spectra of NU02 and KM10 of 2.5x10-2

M in CH3CN

at room temperature. Inset: the picture at room temperature

The result shows that KM10 (516 nm) shows significantly blue

shifted compared with NU02 (536 nm). The observation showed similar

to imtermediate in the previous conditions. The colorimetric n-butylamine sensor data

are summarized in the Table 4.5.

Table 4.5 Summary of maximum absorption wavelength of NU02

NU02 : n-BuNH2 : HCl max (nm)

0 min 5 min 30 min 60 min 120 min

1). 1 eq. : 3 eq. :(excess)

2). 1 eq. : 1 eq. : 0 eq.

3). 1 eq. : 3 eq. : 1 eq.

4). 1 eq. : 3 eq. : 10 eq.

5). 1 eq. : 3 eq. : 100 eq.

6). 1eq. : 1 eq. : 100 eq.

7). 1 eq. : 0 eq. : 100 eq.

536

516

525

527

528

516

519

530

516

525

521

517

516

514

500

518

521

514

462

496

514

482

516

518

508

454

457

510

474

509

510

498

450

448

503

550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0 NU02

KM10N

orm

ali

zed

Ab

sorb

an

ce I

nte

nsi

ty (

a.u

.)

Wavelength (nm)

NU02 and KM10

61

From Table 4.5, the maximum absorption wavelength showed

significant change with the number of HCl. It was found that colormetric sensor was

changed from red to orange.

Afterwards, KM09 was used to study the effect of an electrophile

position. KM09, the ester moieties was placed with para position compared with NU02

(meta-position). The colorimetric n-butylamine sensor was investigated by KM09 with

100 eq. HCl by 1 eq. n-BuNH2. This reaction also was monitored by visible absorption

spectra as shown in Figure 4.35.

Condition 8: 1 eq. KM09 [2.5x10-2 M]: 1 eq. n-BuNH2: 100 eq. HCl

575 600 625 650 675 700

0.0

0.2

0.4

0.6

0.8

1.0 0 min

5 min

30 min

60 min

120 min

No

rma

lize

d A

bso

rba

nce

in

ten

sity

(a

.u.)

Wavelength (nm)

Figure 4.35 Changes in the absorption spectra of KM09 of 2.5x10-2

M and

100 equiv. HCl in CH3CN solution with 1 equiv.n-BuNH2.

Inset: the reaction picture at 0 and 120 min.

Upon addition of reaction time, the absorption wavelength do not

change until 2 hour supported by the unchange color. We conclude that the meta

electrophile position of ester moieties is a suitable position for amine colorimetric sensor.

0 min 120 min

62

CHAPTER 5

CONCLUSIONS

The two series of ionic cyclometalated Ir(III) complexes compose of OLEDs and

colorimetric n-butylamine sensor.

First series, the complexes used for organic light emitting diode (OLEDs);

[Ir(spiro)(ppy)2]PF6 (KM01), [Ir(spiro)(thio)2]PF6 (KM02), [Ir(spiro)(difluoro)2]PF6

(KM03) and [Ir(spiro)(ppz)2]PF6 (KM04), which spiro is 4,5-diaza-9,9´-spirobifluorene,

ppy is 2-phenylpyridine, thio is 2-thiophenyl pyridine, difluoro is 2´,4´-difluorophenyl-

pyridine and ppz is 2´,4´-difluorophenyl 1H-pyrazole. The complexes have been

successfully synthesized. All complexes were characterized by NMR, MS, UV-Vis,

PL and CV. The charged iridium (III) complexes successfully generated emission color

from green, yellow and orange (501-582 nm). Then, KM01-KM04 were fabricated

to OLEDs device based on ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1 by mole)/

TPBi/LiF/Al in acetronitrile solvent. From the results, KM01-KM04 showed

maximum current efficiency at 1.72, 0.07, 1.68, 0.19 cd/A and brightness at 2,027,

130, 879, 27 cd/m2, respectively. We found that KM01 showed maximum current

efficiency at 1.72 cd/A, brightness at 2,027 cd/m2 and CIE coordinates of (0.48, 0.50).

To improve a performance, KM04 was studied with a co-solvent as acetonitrile and

1,2 dichlorobenzene (1:1 v/v) and modified ratio of ionic liquid to (1:0.75).

We found that the better electroluminescence device can be obtained with the current

efficiency to 0.29 cd/A, the maximum brightness at 212 cd/m2.

Second series, the complexes used for colorimetric n-butylamine sensor;

[Ir(L1)(ppy)2]PF6 (NU02) and [Ir(L2)(ppy)2]PF6 (KM09). Which L1 is dimethyl-

2,2´-bipyridine-3,3´-dicarboxylate and L2 is dimethyl-2,2´bipyridine-4,4´dicarboxylate.

We studied the colorimetric n-butylamine sensor by varied the amount of HCl and

n-butylamine. From the studied, the condition of NU02 with 100 equiv. of HCl

changed the color from red to orange after 120 minutes of reaction. The results showed

63

that the absorption bands of KM09 do not change in reaction. Moreover,

we synthesized and studied KM10 which suggested a formation of new chromophore

compared with NU02. This preliminary study could be a benefit system to detect many

narcotic drugs in the future.

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APPENDICES

71

APPENDIX A

Characterization data

72

4000 3500 3000 2500 2000 1500 1000 500

70

75

80

85

90

95

100

3397

A4

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3071

1726

17001623 1395

1220

1065

1137

778

Figure A.1 13

C NMR in DMSO, ATR-FTIR (neat) and mass of A4 at room

temperature

73

4000 3500 3000 2500 2000 1500 1000 500

50

60

70

80

90

100

L1

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3004

2847

1711

1599

1412

1296

1131

762

Figure A.2 13

C NMR in CDCl3 and ATR-FTIR (neat) of L1 at room temperature

74

4000 3500 3000 2500 2000 1500 1000 500

50

60

70

80

90

100

110

YN-13

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3112

2437

1706

1603

1458

1285

1012

755

680

Figure A.3 13

C NMR in DMSO, ATR-FTIR (neat) and mass of YN-13 at room

temperature

75

4000 3500 3000 2500 2000 1500 1000 500

40

50

60

70

80

90

100

110

L2

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3000

29202845

1727

1589

1433

1290

1123

953

747

Figure A.4 13

C NMR in CDCl3, ATR-FTIR (neat) and mass of L2 at room

temperature

76

4000 3500 3000 2500 2000 1500 1000 500

30

40

50

60

70

80

90

100

110

L3

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3252

3069

2957

2867

1631

1579

1411

1316

774

Figure A.5 13

C NMR in DMSO, ATR-FTIR (neat) and mass L3 at room

temperature

77

4000 3500 3000 2500 2000 1500 1000 500

40

50

60

70

80

90

100

110

KM01

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3039

1603

1476

1414

1158 1020

754

Figure A.6 ATR-FTIR (neat) and mass of KM05 at room temperature

78

4000 3500 3000 2500 2000 1500 1000 500

50

60

70

80

90

100

110

KM02

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3057

1601

1470

1152

883

774


79

4000 3500 3000 2500 2000 1500 1000 500

30

40

50

60

70

80

90

100

110

KM03

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3086

1599

1477

12941262

1112

826

753


80

4000 3500 3000 2500 2000 1500 1000 500

60

70

80

90

100

110

KM04

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3086

1613

1480

12571107

1031

817

750


81

4000 3500 3000 2500 2000 1500 1000 500

40

50

60

70

80

90

100

NU02

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3085

1731

2923

1600

1412

1305

1296

830

758

Figure A.10 ATR-FTIR (neat) and mass of NU02 at room temperature

82

4000 3500 3000 2500 2000 1500 1000 500

40

50

60

70

80

90

100

110

KM05

% T

ran

smit

tan

ce

Wavenumber (cm-1)

30432921

1729

16071478

1261

1122

830

753

Figure A.11 1H NMR in CDCl3, ATR-FTIR (neat) and mass of KM09 at room

temperature

83

4000 3500 3000 2500 2000 1500 1000 500

30

40

50

60

70

80

90

100

KM07

Wavenumber (cm-1)

% T

ran

smit

tan

ce

3428

3063

2923

1661

1607

1478

13121151

825

755


84

4000 3500 3000 2500 2000 1500 1000 500

30

40

50

60

70

80

90

100

110

KM08

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3037

3607

1478

1163

835

725

Figure A.13 13

C NMR in CDCl3, ATR-FTIR (neat) and mass of KM01at room

temperature

85

4000 3500 3000 2500 2000 1500 1000 500

20

30

40

50

60

70

80

90

100

KM09

% T

ran

smit

tan

ce

Wavenumber (cm-1)

2950

2855

1604

1473

1157

830

721

Figure A.14 13

C NMR in CDCl3 and ATR-FTIR (neat) and mass of KM02

at room temperature

86

4000 3500 3000 2500 2000 1500 1000 500

20

30

40

50

60

70

80

90

100

110

KM10

% T

ran

smit

tan

ce

Wavenumber (cm-1)

3087

1602

1478

1248

1105

817

729

Figure A.15 13


at room temperature

87

4000 3500 3000 2500 2000 1500 1000 500

20

30

40

50

60

70

80

90

100

110

KM11

% T

ran

smit

tan

ce

Wavenumber (cm-1)

2928

2862

1615

1416

1258 1108

1037

838

725

Figure A.16 13

C NMR in CDCl3, ATR-FTIR (neat) and mass of KM04 at room

temperature

88

APPENDIX B

Conference and publications

89

Oral presentation

The 2013 3rd International Conference on Advanced Materials and Engineering

Materials (3rd ICAMEM 2013) in the title of A Novel charge iridium(III) complex

for amine sensor application, during December 14th-15th, 2013 in Singapore.

90

Publication papers

94

CURRICULUM VITAE

NAME Miss Kattaliya Mothajit

BIRTH DATE 24 June 1989

BIRTH PLACE Sisaket Province, Thailand

EDUCATION B. Sc. (Chemistry), Department of

Chemistry, Faculty of Science, Ubon

Ratchathani University, Ubon

Ratchathani, Thailand, 2008-2011.

M. Sc. (Chemistry), Department of

Chemistry, Faculty of Science, Ubon

Ratchathani University, Ubon

Ratchathani, Thailand, 2011-2015.

RESEARCH GROUP Organometallic and Catalytic Center (OCC)

a novel of new charge iridium complexes for organic light

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