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DFT Studies of Photochromic Mercury
ComplexesKarel G von Eschwege& Jeanet Conradie
T: 051 401 9111 [email protected] www.ufs.ac.za
CONTENT• INTRODUCTION• STRUCTURES & ISOMERS• TDDFT STUDIES• MECHANISM• ACKNOWLEDGEMENTS
INTRODUCTION
PHOTOCHROMIC
REACTION
ABSO
RBAN
CE
WAVELENGTH / nm
N
N
C
N
N
S
Hg
H
O
O
N
N
C
N
S
Hg
N
H
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
