DOI: 10.1002/chem.201202734 Photochemistry of fac-[ReACHTUNGTRENNUNG(bpy)(CO) 3 Cl]** Shunsuke Sato, [a, g] Yasuo Matubara, [a, g] Kazuhide Koike, [b, e] Magnus Falkenstrçm, [d] Tetsuro Katayama, [d, e] Yukihide Ishibashi, [d, e] Hiroshi Miyasaka,* [d, e] Seiji Taniguchi, [c] Haik Chosrowjan, [c] Noboru Mataga † , [c] Naoto Fukazawa, [a] Shinya Koshihara, [a, e] Ken Onda,* [f, g] and Osamu Ishitani* [a, e, h] In memory of Professor Mataga Abstract: The photochemistry of fac- [ReACHTUNGTRENNUNG(bpy)(CO) 3 Cl] (1a ; bpy = 2,2’-bi- pyridine) initiated by irradiation using < 330 nm light has been investigated. Isomerization proceeded in THF to give the corresponding mer-isomer 1b. However, in the presence of a small amount of MeCN, the main product was the CO-ligand-substituted complex (OC-6-24)-[ReACHTUNGTRENNUNG(bpy)(CO) 2 ClACHTUNGTRENNUNG(MeCN)] (2c ; bpy = 2,2’-bipyridine). In MeCN, two isomers, 2c and its (OC-6-34) form (2a), were produced. Only 2c thermal- ly isomerized to produce the (OC-6-44) form 2b. A detailed investigation led to the conclusion that both 1b and 2c are produced by a dissociative mecha- nism, whereas 2a forms by an associa- tive mechanism. A comparison of the ultrafast transient UV-visible absorp- tion, emission, and IR spectra of 1a ac- quired by excitation using higher- energy light (e.g., 270 nm) and lower- energy light (e.g., 400 nm) gave de- tailed information about the excited states, intermediates, and kinetics of the photochemical reactions and pho- tophysical processes of 1a. Irradiation of 1a using the higher-energy light re- sulted in the generation of the higher singlet excited state with t  25 fs, from which intersystem crossing proceeded to give the higher triplet state ( 3 HES(1)). In THF, 3 HES(1) was com- petitively converted to both the triplet ligand field ( 3 LF) and metal-to-ligand charge transfer ( 3 MLCT) with lifetimes of 200 fs, in which the former is a reac- tive state that converts to [Re- ACHTUNGTRENNUNG(bpy)(CO) 2 ClACHTUNGTRENNUNG(thf)] + (1c) within 10 ps by means of a dissociative mechanism. Re-coordination of CO to 1c gives both 1a and 1b. In MeCN, irradiation of 1a by using high-energy light gives the coordinatively unsaturated com- plex, which rapidly converted to 2c.A seven-coordinate complex is also pro- duced within several hundred femto- seconds, which is converted to 2a within several hundred picoseconds. Keywords: isomerization · ligand substitution · photochemistry · pho- tophysics · rhenium [a] Dr. S. Sato, Dr. Y. Matubara, Dr. N. Fukazawa, Prof. S. Koshihara, Prof. O. Ishitani Department of Chemistry Graduate School of Science and Engineering Department of Chemistry and Material Science Graduate School of Science and Engineering Tokyo Institute of Technology, O-okayama 2-12-1, E1-9 Meguro-ku, Tokyo 152-8551 (Japan) E-mail : Ishitani@chem.titech.ac.jp [b] Dr. K. Koike National Institute of Advanced Industrial Science and Technology, Onogawa 16-1 Tsukuba 305-8569 (Japan) [c] Dr. S. Taniguchi, Dr. H. Chosrowjan, Prof. N. Mataga Institute for Laser Technology, Utsubo-Honmachi 1-8-4 Nishi-ku, Osaka 550-0004 (Japan) [d] Dr. M. Falkenstrçm, Dr.T. Katayama, Dr. Y. Ishibashi, Prof. H. Miyasaka Division of Frontier Materials Science Graduate School of Engineering Science Center for Quantum Science and Technology under Extreme Conditions, Osaka University Toyonaka, Osaka 560-8531 (Japan) E-mail: miyasaka@chem.es.osaka-u.ac.jp [e] Dr. K. Koike, Dr. T. Katayama, Dr. Y. Ishibashi, Prof. H. Miyasaka, Prof. S. Koshihara, Prof. O. Ishitani CREST, Japan Science and Technology Agency (JST) Kawaguchi-shi, Saitama 332-0022 (Japan) [f] Prof. K. Onda Interactive Research Center of Science Tokyo Institute of Technology, Nagatsuta, Midori-ku Yokohama, Kanagawa 226-8502 (Japan) E-mail : onda.k.aa@m.titech.ac.jp [g] Dr. S. Sato, Dr. Y. Matubara, Prof. K. Onda PRESTO, JST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan) [h] Prof. O. Ishitani ALCA, JST, Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan) [†] Deceased. [**] bpy = 2,2’-bipyridine. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201202734. It contains Arrhenius plots of the decrease of 1a and the formation of 2a and 2b ; effects of viscosity of the solvent on the decrease of 1a ; time profiles of the IR (1850 and 1988 cm 1 ) absorbance changes for a solution of 1a in THF following excitation with a 266 nm laser pulse; time profiles of UV/Vis absorbance changes for a solution of 1a in MeCN following excitation with a 370 or 270 nm laser pulse. Re-use of this article is permitted in accordance with the Terms and Conditions set out at http://onlinelibrary.wiley.com/journal/10.1002/ACHTUNG- TRENNUNG(ISSN)1521-3765/homepage/2111_onlineopen.html. # 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eur. J. 2012, 18, 15722 – 15734 15722