1. T: +27(0)51 401 9111 | info@ufs.ac.za | www.ufs.ac.za DFT Studies of Photochromic Mercury Complexes Karel G von Eschwege & Jeanet Conradie

2. T: 051 401 9111 info@ufs.ac.za www.ufs.ac.za CONTENT INTRODUCTION STRUCTURES & ISOMERS TDDFT STUDIES MECHANISM ACKNOWLEDGEMENTS

3. INTRODUCTION

4. PHOTOCHROMIC REACTION ABSORBANCE WAVELENGTH / nm The spontaneous radiationless thermal back-reaction of (o-MeO)dithizonatophenylmercury(II) in dichloromethane. Von Eschwege, K. G., J. Photochemistry & Photobiology, 252, 159-166, 2013 h 

5. STRUCTURES & ISOMERS

6. Possible Geometries of the Photo-activated Blue Isomer

9. ORANGE RESTING STATE

10. PHOTO-GENERATED BLUE STATE

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

12. 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.

13. TDDFT STUDIES

14. 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)

17. MECHANISM

18. 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.

19. Conical Intersection C N C N C N Hirai & Sugino, PhysChemChemPhys, 2009, 11:22, 4570-4578

23. Proposed reaction pathway for DPM after S 0  S 1 photo- excitation. After excitation the molecule immediately starts twisting to minimize its energy. This corresponds to a slope down the S 1 potential energy surface and runs into a region of a conical intersection with S 0. After fast vibrational relaxation it proceeds onto S 0 where it bifurcates to orange & blue. Schwoerer, Von Eschwege, Bosman, et al, ChemPhysChem, 2011, 12, 2653-2658 30 fs 1 ps (100 ps in CH 3 OH) (1.5 ps) ( 2 / 3 : 1 / 3 ) PROPOSED PATH FOR UNSUBSTITUTED DPM

24. Von Eschwege, Bosman, Conradie & Schwoerer, J. Phys. Chem. A, 2013, submitted for publication FEMTOSECOND LASER SPECTROSCOPY LASER RESEARCH INSTITUTE, STELLENBOSCH

25. T: +27(0)51 401 9111 | info@ufs.ac.za | www.ufs.ac.za - CHPC - J Conradie - LRI at SU THANK YOU