mogens brøndsted nielsen · smart materials & structures, las vegas, 15-17.6 mogens brøndsted...

Smart Materials & Structures, Las Vegas, 15-17.6

Mogens Brøndsted Nielsen

From Light-Controlled Molecular Electronics Devices to

Solar Energy Storage Materials

Center for Exploitation of Solar Energy &

Department of Chemistry, University of Copenhagen

Photoswitches

Cis-trans isomerizations

Electrocyclic reactions… changes in conjugation

Photoswitches for Molecular Electronics

S S

S S

Auor Ag

Auor Ag

Auor Ag

Auor Ag

off

on

light

state 1

state 2

Conducting Probe

AFM Measurements

J. M. Mativetsky, G. Pace, M. Elbing, M. A. Rampi,

M. Mayor, P. Samorì, J. Am. Chem. Soc. 2008, 130,

9192-9193.

NN

S

NN

S

Au Au

AFM tip

light

off on

AFM tip

A. J. Kronemeijer, H. B. Akkerman, T. Kudernac, B. J.

van Wees, B. L. Feringa, P. W. Blom, B. de Boer, Adv.

Mater. 2008, 20, 1467-1473.

Dithienylethene Photoswitch

S S

AcS SAc

S S

SAc SAc

light

off

on

A. J. Kronemeijer, H. B. Akkerman, T. Kudernac, B. J.

van Wees, B. L. Feringa, P. W. Blom, B. de Boer, Adv.

Mater. 2008, 20, 1467-1473.

Dithienylethene Photoswitch

S S

AcS SAc

S S

SAc SAc

light

off

on

linear conjugation

cross-conjugation

Dihydroazulene (DHA) / Vinylheptafulvene (VHF) Photoswitch

DHA lmax 353 nm

VHF lmax 470 nm

R = Ph:

(solvent: MeCN)

f = 0.55

t½ = 165 min (25oC)

Thermal Conversion of VHF Crystals

Ph

NC CN

Ph

CNNC

Energy barrierfor back-reaction

Energy stored

Photoinducedisomerization

low-energy molecule

high-energy molecule

light

"trigger"

Solar Energy Storage Using Photoisomerization

… Slow switching

Tuning of switching events?

- fast or slow

Many positions available

for substitution

Synthetic protocols for

functionalization?

Can the core be used as substrate

for further reactions?


- fast or slow


for substitution


functionalization?




- fast or slow

many positions available

for substitution

Switch for molecular electronics?

- Incorporation of electrode

”alligator clips”


- fast or slow


for substitution

Switch for molecular electronics?

- Incorporation of electrode

”alligator clips”

Solar energy storage?

Only photoactive in one direction

but can we control the heat release?


functionalization?



DHA Synthesis

… method allows ready incorporation

of an aryl group at position 2

S. L. Broman, S. L. Brand, C. R. Parker, M. Å. Petersen, C. G. Tortzen,

A. Kadziola, K.Kilså, M. B. Nielsen, ARKIVOC 2011, ix, 51-67.

Regioselective Functionalization of DHA

Bromination – Elimination – Cross-coupling protocol

S. L. Broman, M. Å. Petersen, C. Tortzen, A. Kadziola, K. Kilså, M. B. Nielsen,

J. Am. Chem. Soc. 2010, 132, 9165-9174.

M. Å. Petersen, S. L. Broman, A. Kadziola, K. Kilså,

M. B. Nielsen, Eur. J. Org. Chem. 2011, 1033-1039.




J. Am. Chem. Soc. 2010, 132, 9165-9174.



Dibromide:


EWG = electron-withdrawing group

EDG = electron-donating group



J. Am. Chem. Soc. 2010, 132, 9165-9174.



Expanding and Optimizing the Protocol

O O

P(C6H11)2

RuPhos

Pd(OAc)2, RuPhos

NCCN

Y B(OH)2

40-92%

Y

NCCN

Br

X

X

SMe, St-Bu

Me

OMe

NMe2

K3PO4

PhMe / H2O, D

Y

NO2

CN

Br

H

SMe, St-Bu

Me

C6H4OMe

NMe2

X

NO2

CN

Br

H(a few exceptions < 10%)

Ph

SO2t-Bu

SOt-Bu

NH2X = Y = NO2:

28 different combinations

S. L. Broman, M. Jevric, M. B. Nielsen, J. Org. Chem. 2014, 79, 41-64.

CNNC

Ar

ArAr NC CN

Ar

light

D

How fast is the ring-closure reaction?

DHA VHF

30

20

10

0

(1

03 M

-1 c

m-1

)

800700600500400300200

Wavelength (nm)

7-DHA

7/6-DHA

VHFA)

1.0

0.8

0.6

0.4

0.2

0.0

Abs

12080400Time (min)

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Abs

800700600500400300200

Wavelength (nm)

B)

NCCN

Br

-9.5

-9.0

-8.5

-8.0

-7.5

-7.0

ln(k

)

3.353.303.253.203.153.10

T-1

(10-3

K-1

)

ln(k) = -11307 ± 8.59 x T -1

+ 28.264 ± 0.0275

Ea = 94.0 x 103 (± 0.07) J mol

-1

A = 1.88 x 1012

(± 5.25 x 1010

) s-1

C)

Exponential Decay

of VHF absorption

Kinetics Easily Followed by Absorption Spectroscopy

VHF DHA

VHF

DHA

CNNC NC CN

YY

X

X

Ring-Closure Reactions in MeCN at Room Temperature

CNNC NC CN

Half-life = 50 min

Me2NMe2N

X

VHF DHA

CNNC NC CN

Half-life = 490 min

O2NO2N

X

VHF DHA

fast

slow

Electron-donating group at the seven-membered ring enhances the ring-closure

S. L. Broman, M. Jevric, M. B. Nielsen, Chem. Eur. J. 2013, 19, 9542-9548.

Electron-withdrawing group at vinylic position ring enhances the ring-closure

-10.2

-10.0

-9.8

-9.6

-9.4

-9.2

-9.0

-8.8

ln(k

)

0.80.60.40.20.0-0.2-0.4

m / p

p-NO2

p-CN

m-CN

p-CO2Me

p-CHO

m-I

m-SAc

p-CCH

p-I

p-Brp-F

m-CCH

H

p-NHAc

p-OMe

p-Me

CNNC NC CN

X

X

VHF Ring-Closure – Hammett Correlation

p-NO2

p-CN

p-OMe

- Effect of changing the aryl group at the vinylic position

S. L. Broman, M. Jevric, M. B. Nielsen, Chem. Eur. J. 2013, 19, 9542-9548.

m/p (meta or para)

fast

slow

CNNCd+

d-

Ph

Polar Transition State

Electron-donating group at the seven-membered ring enhances the ring-closure

Electron-withdrawing group at vinylic position ring enhances the ring-closure

Calculations reveal a change in dipole moment between VHF

and the transition state of ca. 4 Debye

O. Schalk, S. L. Broman, M. Å. Petersen, D. V. Khakhulin, R. Y. Brogaard, M. B.

Nielsen, A. E. Boguslavskiy, A. Stolow, T. I. Sølling, J. Phys. Chem. A. 2013.

Our data

Daub et al., J. Phys. Chem.

1993, 97, 4110.

Solvent polarity

ET(30) / kcal mol-1

Solvent Effects – Further Support for Polarized TS

S. L. Broman, S. L. Brand, C. R. Parker, M. Å. Petersen, C. G. Tortzen,

A. Kadziola, K.Kilså, M. B. Nielsen, ARKIVOC 2011, ix, 51-67.

Molecular Switch for Molecular Electronics

SRMe

weak contact

strong contact

Au

SR

Au

SR

Ac

cleavable protecting group

S S

S S

DHAAu

or AgAu

or Ag

VHFAu

or AgAu

or Ag

lightheat

NCCN

Br2

I

CH2Cl2>99%

NCCN

BrBr

LiHMDS

THF

>90%

NCCN

MeS

SMe

MeS B(OH)2

Pd(PPh3)4, KF

toluene, H2O

80%

NCCN

SMe

SMe

NCCN

SMe

Br

>99% (crude)

MeS B(OH)2

Pd(PPh3)4, KF

toluene, H2O

Incorporation of Methylthio End-Groups – ”Alligator Clips”

(17%)

S. L. Broman, S. Lara-Avila, C. L. Thisted, A. D. Bond, S. Kubatkin,

A. Danilov, M. B. Nielsen, Adv. Funct. Mater. 2012, 22, 4249-4258.

Molecular Electronics: Single-Molecule Junction (4 K)

Samuel Lara-Avila, Andrey Danilov, Sergey Kubatkin, Chalmers University of Technology

Silver electrodes

1) Sublimation of silver

2) Sublimation of molecules

3) Molecules land on substrate at 4 K

4) Surface diffusion is activated at 30-60 K

5) Cooling back to 4 K after capture of molecule

The Single Electron Transistor

• The structure: a gate, two electrodes, and a molecule

• Coulomb Blockade Regime

• Well defined transport

• The transport can be controlled by VSD (bias potential) and VG (gate potential)

Department of Chemistry

Stability plot: A set of differential conductance

curves taken at different gate

voltages

Coulomb blockade diamonds

The molecule is weakly coupled

to electrode

- electron hopping mechanism



Molecular Electronics: Single-Molecule Junction (4 K)

on

on

offoff

DHA

(off)

VHF

(on)

Increase of bias voltage

from 25 to 80 mV

Light

Reversible Switching at Gate Potential of 2.6 V

Increase of temperature

from 4 to 25 K

Light



Ultrathin Reduced Graphene Oxide

Films as Transparent Top-Contacts

CN

CNCN

CN

VHF

DHA

SS

Au Au

UV

heat

meta-configuration

to avoid quenching

of photoactivity

Adv. Mater. 2013, 25, 4164-4170.

Collaboration with Tao Li, Kasper Nørgaard, Bo W. Laursen

DHA

AcS

Ultrafast Ring-closure of VHF

in Locked s-cis Conformation

1.0

0.8

0.6

0.4

0.2

0.0

Ab

s

800700600500400300

Wavelength (nm)

DHA

VHF

Half-life: < 2 s (cyclohexane)

NC CN NC CN

S. L. Broman, J. Daub, M. B. Nielsen

et al., EurJOC, In press

Incorporation of Anchoring Groups

… reactive triflate

NC

CNCN

CN

CN

CNCNNC CNNCNC CN

light light

DHA Double Switch – Stepwise Ring-Openings

A.U. Petersen, S.L. Broman, S.T. Olsen, A.S. Hansen, L. Du,

A. Kadziola, T. Hansen, H.G. Kjaergaard, K.V. Mikkelsen,

M.B. Nielsen, Chem. Eur. J. 2015, 21, 3968-3977.

… quenching of

photoactivity by

nearby electron

acceptor

CN

CN

Acceptor

hn e

Energy barrierfor back-reaction

Energy stored

Photoinducedisomerization

low-energy molecule


light

"trigger"

Solar Energy Storage Using Photoisomerization

… Material with energy density of 1 MJ / kg

• Heat release of 1 MJ can be used to bring 3 L of water

from room temperature to the boiling point

• Harvesting light during the day and releasing heat during the night:

- maintaining 1 m3 at 19 oC with outside temperature of -6 oC requires

ca. 3 kg of solar battery (when using foam insulation)

T. R. Kucharski, Y. Tian, S. Akbulatov, R. Boulatov, Energy Environ. Sci. 2011, 4, 4449-4472.

Energy Storage

Ph

NC CN

Ph

NC H

Ph

Ph

NC H

Ph

NC CN

Ph

0.11 MJ / kg 0.25 MJ / kg

0.15 MJ / kg 0.23 MJ / kg

S.T. Olsen, J. Elm, F.E. Storm, A.N. Gejl, A.S. Hansen, M.H. Hansen, J.R. Nikolajsen, M.B. Nielsen,

H.G. Kjaergaard, K.V. Mikkelsen, J. Phys. Chem. A 2015, 119, 896-904.

M. Cacciarini, A.B. Skov, M. Jevric, A.S. Hansen, J. Elm, H.G. Kjaergaard, K.V. Mikkelsen, M.B. Nielsen,

Chem. Eur. J. 2015, 21, 7454-7461.

storedenergy

By minor structural variations we can double the energy density!

Substitute one

CN for a H

M06-2X

(vacuum)

Reductive Decyanations

TS calculations:

DG‡ = 125.7 kJ/mol

Half-life >10 years at rt

M. Cacciarini, A.B. Skov, M. Jevric, A.S. Hansen, J. Elm, H.G. Kjaergaard, K.V. Mikkelsen, M.B. Nielsen,

Chem. Eur. J. 2015, 21, 7454-7461.

.

Ph

NC CN hn

Ph

H CNDIBAL-H

THF Ph

CNH

23%

Ph

NC CN hn

Ph

H CNDIBAL-H

THF

Ph Ph

Ph

CNH

Ph16%veryslowly

VHF of this DHA:

Half-life of 14 s

Halting the Energy-Releasing Back-Reaction

Chem. Eur. J. 2015, 21, 7454-7461.

… We are currently working on triggering the energy release by a catalyst

Ph

H CN

Ph

Ph

HNC

Ph

light

Half-life of years!

low-energy molecule


light

energy release

Effect of Ag+ on the thermal ring-closure reaction of VHF:

C. R. Parker, C. G. Tortzen, S. L. Broman, M. Schau-Magnussen,

K. Kilså, M. B. Nielsen, Chem. Commun. 2011, 47, 6102-6104.

Triggering the Ring-Closure

Solvent: 1,2-dichloroethane

min

CNNC

Ph

NC CN

Ph

Ag+

NC CNNC CN light

seconds

EurJOC, In press.

The Other Extreme: A Very Fast Photoswitch

Light-Harvesting followed by Immediate Energy Release

low-energy molecule


light

energy release

Conclusions

• Efficient synthetic protocol for functionalization of the dihydroazulene/

vinylheptafulvene system in its seven-membered ring:

”addition – elimination – cross-coupling protocol”

• Tuning of switching events by donor-acceptor substitution and

solvent polarity

• Light-triggered conductance switching in single-molecule

dihydroazulene/vinylheptafulvene junctions

• Minor structural changes can increase the energy storage capacity

and the heat release from seconds to years

University of Copenhagen

Dr. Michael Åxman Petersen

Dr. Christian Parker

Dr. Martyn Jevric

Dr. Søren Lindbæk Broman

Louise Skov

Anne U. Petersen

Virginia Mazzanti

Marco Santella

Henriette Lissau

Alexandru Vlasceanu

Kasper Fjelbye

Anders Bo Skov

Christian Tortzen

University of Florence / Cph

Dr. Martina Cacciarini


Prof. Kurt V. Mikkelsen

Prof. Henrik G. Kjærgaard

Assoc. Prof. Theis Sølling

Prof. Bo W. Laursen

Assoc. Prof. Kasper Nørgaard

Assoc. Prof. Anders Kadziola

Prof. Andrew Bond

Dr. Jonas Elm

Stine T. Olsen

Chalmers University of Technology

Prof. Sergey Kubatkin

Dr. Andrey Danilov

Dr. Samuel Lara-Avila

€€€

The Danish Research Agency (FNU, FTP)

EU – 7th Framework Program

The Lundbeck Foundation

The Carlsberg Foundation

The Villum Kann Rasmussen Foundation

Danish-Chinese Center for Nanoelectronics


– Center for Exploitation of Solar Energy

Acknowledgements

mogens brøndsted nielsen · smart materials & structures, las vegas, 15-17.6 mogens brøndsted...

Documents