DFT Studies of Photochromic Mercury Complexes

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DFT Studies of Photochromic Mercury

ComplexesKarel G von Eschwege& Jeanet Conradie

T: 051 401 9111 info@ufs.ac.za www.ufs.ac.za

CONTENT• INTRODUCTION• STRUCTURES & ISOMERS• TDDFT STUDIES• MECHANISM• ACKNOWLEDGEMENTS

INTRODUCTION

PHOTOCHROMIC

REACTION

ABSO

RBAN

CE

WAVELENGTH / nm

NN

CN

N

S

Hg

H

O

O

NN

CN

S

Hg

NH

O

O

The spontaneous radiationless thermal back-reaction of(o-MeO)dithizonatophenylmercury(II)in dichloromethane.

Von Eschwege, K. G., J. Photochemistry & Photobiology, 252, 159-166, 2013

hn

D

STRUCTURES & ISOMERS

Possible Geometries of the Photo-activated Blue Isomer

ORANGE RESTING STATE

PHOTO-GENERATED BLUE STATE

Von Eschwege, Bosman, Conradie & Schwoerer, J. Phys. Chem. A, 2013, submitted for publication

b c

a d

PhHgHDz geometries and orbitals during the photo-isomerization reaction:(a) orange resting state (0 kJ mol-1), (b) vertically excited state (259 kJ mol-1), (c) blue excited state (228 kJ mol-1), and (d) blue ground state (17 kJ mol-1). The C=N double bond becoming single, allows free rotation.

TDDFT STUDIES

Von Eschwege, Bosman, Conradie & Schwoerer, J. Phys. Chem. A, 2013, submitted for publication

GAS DCM MeOH

COMP.: 457 nm 477 nm 476 nm

EXP.: 474 nm

Unsubstituted DPM (orange)

MECHANISM

ADF calculated potential energy of DPM along the -C=N- twist coordinate, displaying minima in the planar configurations and ground state E barrier at orthogonal geometry.

Conical Intersection

C

N

C

N

CN

Hirai & Sugino, PhysChemChemPhys, 2009, 11:22, 4570-4578

Proposed reaction pathway for DPM after S0 S1 photo-excitation. After excitation the molecule immediately starts twisting to minimize its energy. This corresponds to a slope down the S1 potential energy surface and runs into a region of a conical intersection with S0. After fast vibrational relaxation it proceeds onto S0 where it bifurcates to orange & blue.

Schwoerer, Von Eschwege, Bosman, et al, ChemPhysChem, 2011, 12, 2653-2658

30 fs

1 ps

(100 ps in CH3OH)

(1.5 ps)(2/3 : 1/3)

PROPOSED PATH FOR UNSUBSTITUTED DPM

Von Eschwege, Bosman, Conradie & Schwoerer, J. Phys. Chem. A, 2013, submitted for publication

FEMTOSECOND LASER SPECTROSCOPY

LASER RESEARCH INSTITUTE, STELLENBOSCH

T: +27(0)51 401 9111 | info@ufs.ac.za | www.ufs.ac.za

- CHPC- J Conradie- LRI at SUTHANK YOU