Novel photonic materialsNovel photonic materials

  Manthos G. PapadopoulosManthos G. Papadopoulos

      

Institute of Organic and Pharmaceutical Chemistry.Institute of Organic and Pharmaceutical Chemistry.National Hellenic Research FoundationNational Hellenic Research Foundation

48 Vas. Constantinou Av.48 Vas. Constantinou Av.Athens 11635Athens 11635

We will consider a series of derivatives,

which have interesting

linear and nonlinear optical properties

and possible applications

in the photonic industry

Unifying features of this work:

•Molecules with large NLO properties

and how these can be interpreted

•Discovery of mechanisms in order

to modify the L&NLO properties

More specifically, we shall comment on the results of three projects:

1. The L&NLO properties of derivatives involving noble gas atoms

2. The L&NLO properties of [60]fullerene derivatives

3. The structure and properties of Ni-dithiolenes

Definition of the electric properties  E = E(0) -μαFα - (1/2)ααβFαFβ - (1/6)βαβγFαFβFγ

  - (1/24)γαβγδFαFβFγFδ - ...

 

 μα : Dipole moment

 

 ααβ: Polarizability

  

βαβγ: First hyperpolarizability

  

γαβγδ: Second hyperpolarizability

Why the L&NLO properties are important: Theory

Study of L&NLO processes (e.g. Kerr effect) Intermolecular interactions

Applications  Design and study of NLO materials (optical processing of information, optical computing)

Noble gas derivatives

Definition of the project:

We consider insertion of a noble gas atom, Ng, in the chemical bond A-B, leading to A-Ng-B.

Specific examples we will consider involve insertion of:

Ar in HF leading to HArF

Xe in HCnH leading to HXeCnH

Xe in AuF lading to AuXeF

Why are the noble gas derivatives interesting and significant?

It is amazing what a noble gas atom, in the middle of a single bond can do, for example it leads to:

large NLO properties,

significant charge transfer etc

Which is the expanation?

HArF

A. Avramopoulos, H. Reis, J. Li and M. G. Papadopoulos, J. Am. Chem. Soc., 126, 6179 (2004).

Properties of noble gases

Synthesis of HArFa (argon fluoro-hydride)[first covalent neutral cond. argon der.]

photolysis of HF in solid argon matrix

Point of interest:

The effect of Ar on the NLO properties of the resulting derivative

a. L. Khriachtchev et al., Nature, 406, 874 (2000)

   μz

 

αzz 

βzzz 

PolHFMP2CCSD(T)   aug-cc-pV5ZHFMP2 

 

3.1392.6912.578

 

  

3.0852.653

 

37.61 55.3759.80

 

   

37.8054.01

 

-597.8-1220.9-1418.1

 

   

-578.7-1102.5

 

The dipole moment, polarizability and

first hyperpolarizability of HArF (in a.u.)

Rationalization of βzzz

μgg: ground state dipole momentμee: excited state dipole momentμge: transition dipole momentΕge: transition energy

2)geE(

2)ge)(ggee(3)0(

μgg: 3.473/0.745 a.u.μee: -0.814/-0.907 a.u.μge: 1.419/-0.611a.u.Εge: 0.276/0.570 a.u.Method: HF/Pol, CIS/Pol

All the above properties contribute so that βzzz of HArF is much larger than that of HF

Comparison of HArF with HF

HArF βzzz=-561.5 a.u. HF/Pol -340.7 a.u. TSM

HF βzzz=-7.4 a.u. HF/Pol -5.7 a.u. TSM

Reliabity of TSM

Reliability of TSM

Large effect of Ar

HF…Ar van der Waals complex

μz=0.983 a.u. (3.473 a.u.)

αzz=19.11 a.u. (34.25 a.u.)

βzzz = -35.09 a.u. (-561.5 a.u.) ratio=16

Charge of Ar: 0.02 (0.56) ratio=28

Method: HF/Pol

Comparison of HArF with

C6H6

Αzz = 44.74 a.u. (34.25 a.u.)

Method: MP4[SDQ]

P-nitro-aniline

βzzz = 797.5 a.u. ( -561.5 a.u.)

Method: HF/Pol

The linear and nonlinear optical

properties of derivatives with inserted

Xe

The first Xe derivative was reported by Bartlet in 1962[Proc. Chem. Soc., 218(1962)]

A large number of Xe compounds have been reported since then

HXeF, AuXeF, XeAuF

F. Holka,A. Avramopoulos, O. Loboda, V. Kellö, M. G. Papadopoulos,Chem. Phys. Letters, 472, 185 (2009)

Points of interest:Points of interest:

•Effect of Xe

•Comparison of H with Au

HXeF, AuXeF: not synthesized yet

XeAuF: several NgMF have been synthesized

Ng: Ar, Kr, XeM: Cu, Ag, AuX: F, Cl, Br

Bonding:

Xe - Au bond: covalent [1]

Au - Xe [AuXeF] bond: partially covalent

(AXe)+ F- : significant charge transfer A= H, Au

1. S. A. Cook and M. C. L. Gerry, J. Am Chem. Soc. 126, 17000 (2004).

The barrier height

AuXeF: 119 kJmol-1

separates the global minimum (AuF+Xe) from the local minimum

AuXeF XeAuF

Xe 0.498 0.159

Au 0.377 0.650

F -0.876 -0.810

NBO charges

Similar charges on F

Quite different charges for Xe of XeAuF and AuXeF

Method: HF/aug-cc-pVQZ

μz αzz βzzz

HXeF 2.019 59.7 -571

AuXeF 2.243 184.3 -2441

XeAuF 2.612 76.4 -265

L&NLO properties

Method: CCSD(T)Basis set: aug-cc-pVQZECP: Au(60), Xe(28)

The position of Xe has a great effect on αzz and βzzz

βzzz (AuXeF) / βzzz (AuF) = 6.0

βzzz (XeAuF) / βzzz (AuF) = 0.7

βzzz (HXeF) / βzzz (HF) = 57.0

Method: CCSD(T)Basis set: aug-cc-pVQZ

Xe may greatly affect βzzz

NR R

μz 3.675 2.047

αzz 211.52 188.06

βzzz -13520 -1826

Relativistic contribution: AuXeF

Methods: CCSD(T), Douglas-KrollBasis sets: PolX, PolX_DK

βzzz = great effect of relativistic contribution

Novel compounds derived by

Xe inserted into HC2H and HC4H:

L&NLO properties

A.Avramopoulos, L. Serrano-Andres, J. Li, H. Reis and M. G. Papadopoulos, J. Chem. Phys., 127, 214 (2007).

Preparation

HXeC2H and HXeC2XeH:They are prepared in a low-temperature Xe matrix using UV photolysis of C2H2 and subsequently annealing at 40-45K[JACS, 125, 4696 (2003)]

HXeC4H:Tanskanen et al. reported its preparation

[JACS, 125, 16361 (2003)]

HC2XeC2H:

Ansbacher et al. predicted that the diacetylide Xe exists as a metastable chemically-bound compound[PCCP, 8, 4175 (2006)]

Structures Weight (%)a

H–Xe+C–CH (I) 44

H·Xe·CCH (II) 26

H–Xe+–CCH (III) 14

H–Xe2+C–CH (IV) 11

H+XeC–CH (V) 5  

Method:CASVB(6,4)/3-21G*

Resonance structures of HXeC2H

Charge transfer in HXeC2H

Intra-molecular

Inter-molecular

NBO Charge Distribution

•1 and 2 Xe atoms:Approx. the same charge

•The chain length does not appear to have an effect

Method:HF/aug-cc-pVZ

•1 Xe atomEnd:0.79 eMiddle:1.02 e

•3 Xe atoms:The middle one has much larger charge

Inter-molecular charge transfer{Xe matrix}/HXeC2H

Two models(a) 6 Xe atoms octahedrally placed around HXeC2HA1A2=7.56 a.u.A2A3=9.45 a.u.Method:MP2/aug-cc-pVDZ

(b) 8 Xe atoms arranged in a cube A1A2=15.12 a.u.

NBO analysis:

insignificant CT takes place from the Xe environment to HXeC2H:

0.02e in the first model and

0.002e in the second model

HXeC2H

HC2H

Method:CCSD(T)/B1

The effect of Xe

Is significant

HXeC2XeHHXeC2H

Method: MP2/B1

The effect of1 and 2

Xe atoms

H2C2H

H2C4H

Δγzzzz = 30 000 au (approx.)

H2XeC2H

H2XeC4H

Δγzzzz = 340 000 au (approx.)

The effect of Xein connection with effect

of the chain length

H-Xe-CC-CC-H γzzzz =111 190 a.u

H-CC-Xe-CC-H γzzzz =28 488 a.u.

H-CC-CC-H γzzzz = 31 224 a.u.

Xe leads to a reduction of γzzzz !

The position of Xe has a significant effect on γzzzz

Method: MP2/aug-cc-pVDZ

Decomposition channels of HXeC2H

H+ Xe + C2H

HXeC2H

Xe + HC2H

34 kcalmol-1

104 kcalmol-1

The barrier to this exothermic reaction is very high, 64.6 kcalmol-1

and prevents the molecule from dissociation

T. Ansbacher et al., PCCP, 8, 4175 (2006)

Vibrational properties

Example: HXeC2H

αpvzz = [μ2](0,0) = 60.13 a.u

Vibrational Modes:

H-Xe: 1681cm-1 [μ2](0,0) = 13.1 a.uXe-C: 313 cm-1 [μ2](0,0) = 46.8 a.u

The other modes have a negligible contribution (0.23 a.u.)

Method:MP2/aug-cc-pVDZ

βpvzzz = [μα](0,0) = -835 a.u.

Vibrational Modes:

H-Xe: 1681cm-1 [μα](0,0) = 1212 a.uXe-C: 313 cm-1 [μα](0,0) = -2079 a.u

The other modes have a very small contribution (32 a.u.)

Method:MP2/aug-cc-pVDZ

Local field effect

The Xe derivatives have been synthesized in a Xe matrix

Thus it would be useful to compute the effect of the Xe environment on the L&NLO properties

Example: HXeC2H

The discrete local field approximation has been applied

Only the dipole and induced dipole interactions between HXeC2H and the Xe environment are considered

Local field expression:

 

 ,

][)( ',')11(,'

'

1cell0 kkkkk

N

kkk FLVF

Where

N is the number of molecules in the cell

Vcell is the volume of the cell

ε0 is the permitivity of vacuum

α,β,γ are the Cartesian components

Fk’α is the permanent local field effect on molecule k’ due to the surrounding molecules

μk’β is the dipole moment of the free molecule k’

αk’αβ is the polarizability of the free molecule k’

L(11) is the Lorentz-factor tensor

Model:

Cubic closed packed with dimensions a=b=c=24.8092 ÅIt involves 255 Xe atoms

H Xe C C H

Y

Z

X

Employed data:

HXeC2H: Dipole moment and polarizability of at the CCSD(T) level and

Xe: experimental polarizability value (27.10 au)

Results:

Local field: Fz=-4.4x10-3 au

μz: 50.5%αzz: 2.5%βzzz: 20.2%γzzzz: 12.7%

Changes of properties

Interpretation of the results

Insertion of Xe in HCnH leads to a large increase of γzzzz

For example:

γzzzz(HXeC2H)=38740 au γzzzz(HC2H)=3380 au

Ratio=11.5

Why?

Method: CASSCF/CASPT2Basis set:ANO-RCCXe:7s6p4d2f1gC:4s3p2d1fH:3s2p1dCASSSF(10,14)

The computations have shown that insertion of Xe leads to:

(a) Excited states of lower energy

(b) An electronic spectrum which is more dense in low lying states

(c) Many non-zero contributions to the transition dipole moment matrix

The NLO properties are:

proportional to products of TDM matrix elements and

inversely proportional to products of energy differences

Therefore an enhancement to NLO properties is expected

The SOS model

SOS computed properties

HC2H HXeC2H

αzz = 11.07 au αzz = 26.51 au

γzzzz = 3473 au γzzzz = 9102 au

The SOS model reflects the expected trend

On the electronic structure of H-Ng-Ng-F

(Ng=Ar, Kr, Xe) and the L&NLO properties

of HXe2F

A.Avramopoulos, L. Serrano-Andre, J.Li, M. G. Papadopoulos, J. Chem. Theory Comput. 6, 3365 (2010).

Questions:

The diradical character of HNg2F

and the L&NLO properties

Methods:

CASVB, MS-CASPT2, CCSD(T)

Electronic ground state description

HArArF: 38% σ2 + 56% σσ*HΚrΚrF: 53% σ2 + 39% σσ*HΧeXeF: 58% σ2 + 35% σσ*

Increase of the closed shell character:

Xe > Kr > Ar

Method: MS-CASPT2/ANO

CASVB computations show:

The total weight of the resonance structureswith diradical character is approx.:

99% for HArArF

97% for HKrKrF

87% for HXeXeF

The singlet-triplet (3Σ+) gap (STG)

provides an indication for the diradical

character of the system:

STG

HAr2F 4.7 kcal/mol

HKr2F 14.7 kcal/mol

HXe2F 28.7 kcal/mol)

Wirz suggested that a diradical is a molecule with

STG which does not differ by much more than

≈ 2kcal/mol.

The expression “diradicaloid”

would then extend this range to ≈ 24 kcal/mol.

So, all the HNg2F are diradicaloids.

HF HXeF HXe2F

μz 0.703 1.975 3.788

αzz 6.19 59.59 420.4

βzzz -11.5 -582.1 -11040

γzzzz x 10-3 0.284 22.7 -4000

Method: CCSD(T)/aug-cc-pVDZ

Stability, Electronic Structure

and L&NLO Properties of

HXeOXeF and FXeOXeF

A.Avramopoulos, J. Li, G. Frenking, M. G. Papadopoulos, J. Phys. Chem. A, 115, 10226 (2011)

HXeOXeF (FXeOXeF) results

from introduction of 2 Xe atoms

in HOF (FOF)

We have shown that the novel derivatives

HXeOXeF and FXeOXeF

can be synthesized, because they are

protected by high energy barriers

VB orbitals of HXeOXeF

CASPT2/ANOCCSD/aug-cc-pVDZMP2/aug-cc-pVDZ

Description of the ground state

HXeXeF 58.0% σ2 + 35% σσ*

HXeΟXeH 77.0% σ2 + 9% σσ*

FXeΟXeF 76.5% σ2 + 10% σσ*

Insertion of O increasesthe closed character

E1 = 14.9E2 = 25.5E3 = 90.3

Units: kcal/mol

Dissociation paths of HXeOXeF calculated at the CASPT2/ANO level.

E4 = 50.1 kcal/molE5 = 31.9 kcal/molE6 = 20.1 kcal/mol

Method: CASPT2/ANOZPE has been taken into accountReactants and products were connected through Intrinsic Reaction Coordinate (IRC) calculations

HOXeF is another novel derivative

HXeOXeF is a local minimum and is higher in energy

than several of its dissociation products:

E(HXeOXeF) – E(HOF + 2Xe) = 125.4 kcal/mol

E(HXeOXeF) – E(HO + F + 2Xe) = 85.2 kcal/mol

E(HXeOXeF) – E(OF + H + 2Xe) = 9.0 kcal/mol

HXeOXeF: Metastable

E1= 49.5 kcal/mol E2= 40.5 kcal/mol E3= 32.1 kcal/mol

Dissociation paths of FXeOXeF calculated at the CASPT2/ANO level

E4 = 30.1 kcal/molE5 = 13.2 kcal/molE6 = 11.1 kcal/mol

Frenking et al. [1] found that HArArF and HKrKrFare associated with low-energy barriers.Thus, they can NOT be observed.

But,HXeXeF 13.1 kcal/molHXeOXeF 14.9 kcal/molFXeOXeF 40.5 kcal/mol

Thus O and F increase the barrier and thusFArOArF and FKrOKrF may be observed.

G. Frenking et al., Angew. Chem. Int. Edition, 48, 366 (2009).

HXeXeFa HXeOXeF HXeOXeH FXeOXeF

μz3.788 2.747 0.987 0.623

αzz420.4 92.8 107.3 90.5

βzzz-11040 -1720 -49 -89.0

Method: CCD(T)/aug-cc-pVTZa. aug-cc-pVDZ

L&NLO Properties

Insertion of O reduces the L&NLO properties

The L&NLO properties of some

Ni-Dithiolene derivatives

Luis Serrano-Andrés, A. Avramopoulos, J. Li, P. Labéquerie, D. Begué,V. Kellö, M. G. Papadopoulos, J. Chem Phys., 131, 134312 (2009).

Points of interest:

• The low-lying excited states of NiBDT

• The impressive NLO properties and their interpretation

a 11Ag [71% ()2()

0−21% ()0()

2].b The energy difference is within the method accuracy. For simplicity

the 11Ag state will be considered the ground state at this level.c 11B1u state 65% [(π 2)

1(π 3)1].

d 13B1u state 92% [(π 2)1(π 3)

1].

State ΔE/eV Main configuration

11Ag ( diradicaloid)a −0.004b … (π2)2(π3)

0 - (π2)0(π3)

2

11B1u (*)c

0.000b … (π2)

1 (π3)1

. . 14 states .

31B3u (σSNi ππ π *) 3.064 … (σSNi)1 (π 1)

1 (π 2)2 (π 3)

2

13B1u (diradical)d 0.612 … (π 2)1 (π 3)

1

 

Excited states structure of Ni(SExcited states structure of Ni(S22CC22HH22))22

Basis set: ANO-RCCBasis set: ANO-RCC

Method: CASSCF/CASPT2Method: CASSCF/CASPT2

Remarks:

The main findings of the CASSCF/CASPT2 computations are:

The quasidegenaracy of 11Ag and 11B1u and the large number of low lying excited states.

These features are very likely to lead to large NLO properties

Table 4. A Basis set study of NiBDTa. The UBHandBHLYP functional was employed. All values are in au.

 

PropertyBasis set

αzz γzzzzx10-4

6-311G* 222.0 68.1

SDD[Ni]/6-31G*

221.9 55.8

ZPolX 245.3 67.7

aug-cc-pVDZ 244.7 71.9

aug-cc-pVTZ 245.2 68.0

aug-cc-pVQZ 245.4 67.6

                a The B3LYP/SDD optimized geometry was employed to all calculations.

Properties of Ni(SProperties of Ni(S22CC22HH22))22

Method: UBHandHLYPMethod: UBHandHLYP

PropertyMethod

αzz γzzzzx10-4

UBHandHLYP 245.3 67.7

UCCSD 300.5 72.4

UCCSD(T) 364.3 119.0

CASSCF/CASPT2m/a1b1b2a2

b

  

  

12/4242 (42,4*2*) 67.9/282.2 1647.5/216.0

16/4444 (44,4*4*) 243.2/340.7 1102.7/184.7

20/4646 (46,4*6*) 309.3/363.8 869.5/153.1

a The properties were computed numerically. Base field: 0.005 au. b m: Number of active electrons; a1b1b2a2: Number of orbitals

in subspaces of C2v symmetry.

Basis set: ZPolXBasis set: ZPolX

Method: UBHandHLYP/

6-31G*

Main points

The big second hyperpolarizability of NiBDT has been interpreted in terms of the quasidegeneracy of the 11Ag and 11B1u states.As well as the many low lying excited states.

The considered Ni-dithiolene derivatives havevery big NLO properties.

The L&NLO properties of [60]fullerene

derivatives

O. Loboda, R. Zalesny, A. Avramopoulos, J. –M. Luis, B. Kirtman, N. Tagmatarchis, H. Reis and M. G. Papadopoulos, J. Phys. Chem. A, 113, 1159 (2009).

Points of interest:

Selection of the appropriate method (e.g. functional)

Computation of the electronic and vibrational contributions

Selection of functional groups

OvershootingEffect:3-55 larger

Comment: The substituents were selected according to increasing Hammett σp constant, which may be used as a measure of their electron donating capabilities. Methods: BLYP and HF(it does not have the overshoot problem).

Ratio:2

Remark:The ratio of the BLYP and the HF values increases monotonically and becomesquite large for the strongest donors.

Ratio:41

Concluding remarks

Mechanisms which lead to large NLO properties have been discussed

Novel derivatives with possible photonic applications have been proposed

Acknowledgement

Colleagues who contributed to this work:

Dr Aggelos Avramopoulos, NHRF, GreeceDr Heribert Reis, NHRF, GreeceDr Luis Serrano Andrés, Universitat de València, SpainDr Jiabo Li, SciNet Technologies, USADr Robert Zalesny, NHRF, GreeceDr Oleksandr Loboda, NHRF, GreeceProfessor B. Kirtman, University of California, USADr Josep Maria Luis, University of Girona, SpainDr Nikos Tagmatarchis, NHRF, GreeceProfessor Vladimir Kellö, Comenius University, Slovakia