Time-resolved synchrotron diffraction and theoretical studies of very short-lived photo-induced molecular species.
Definitive experimental results on the geometry of fleeting species are at the time of writing still limited to monochromatic data collection, but methods for modifications of the polychromatic Laue data to increase their accuracy and their suitability for pump-probe experiments have been implemented and are reviewed. In the monochromatic experiments summarized, excited-state conversion percentages are small when neat crystals are used, but are higher when photoactive species are embedded in an inert framework in supramolecular crystals. With polychromatic techniques and increasing source brightness, smaller samples down to tenths of a micrometre or less can be used, increasing homogeneity of exposure and the fractional population of the excited species. Experiments described include a series of transition metal complexes and a fully organic example involving excimer formation. In the final section, experimental findings are compared with those from theoretical calculations on the isolated species. Qualitative agreement is generally obtained, but the theoretical results are strongly dependent on the details of the calculation, indicating the need for further systematic analysis.
Coppens
Philip
P
Chemistry Department, University at Buffalo, State University of New York, Buffalo, NY 14260-3000, USA. coppens@buffalo.edu
Benedict
Jason
J
Messerschmidt
Marc
M
Novozhilova
Irina
I
Graber
Tim
T
Chen
Yu-Sheng
YS
Vorontsov
Ivan
I
Scheins
Stephan
S
Zheng
Shao-Liang
SL
D003198:Computer Simulation; D018360:Crystallography, X-Ray; D054018:Lasers, Excimer; D008027:Light; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical; D010777:Photochemistry; D017356:Synchrotrons; D013997:Time Factors; D014961:X-Ray Diffraction / Q000379:methods*
D008670:Metals