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Excited-State Dynamics offac-[Re^I(L)(CO)_3(phen)]^+ and fac-[Re^I(L)(CO)_3(5-NO_(2-)phen)]^+(L = Imidazole, 4-Ethylpyridine; Phen = 1,10-Phenanthroline) Complexes

Busby, Michael and Gabrielsson, Anders and Matousek, Pavel and Towrie, Michael and Di Bilio, Angel J. and Gray, Harry B. and Vlček, Antonín, Jr. (2004) Excited-State Dynamics offac-[Re^I(L)(CO)_3(phen)]^+ and fac-[Re^I(L)(CO)_3(5-NO_(2-)phen)]^+(L = Imidazole, 4-Ethylpyridine; Phen = 1,10-Phenanthroline) Complexes. Inorganic Chemistry, 43 (16). pp. 4994-5002. ISSN 0020-1669. doi:10.1021/ic035471b.

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The nature and dynamics of the lowest excited states of fac-[Re^I(L)(CO)_3(phen)]^+ and fac-[Re^I(L)(CO)_3(5-NO_2-phen)]^+ [L = Cl-, 4-ethyl-pyridine (4-Etpy), imidazole (imH); phen = 1,10-phenanthroline] have been investigated by picosecond visible and IR transient absorption spectroscopy in aqueous (L = imH), acetonitrile (L = 4-Etpy, imH), and MeOH (L = imH) solutions. The phen complexes have long-lived Re^I → phen ^3MLCT excited states, characterized by CO stretching frequencies that are upshifted relative to their ground-state values and by widely split IR bands due to the out-of-phase A‘(2) and A‘ ‘ ν(CO) vibrations. The lowest excited states of the 5-NO_(2-)phen complexes also have ^3MLCT character; the larger upward ν(CO) shifts accord with much more extensive charge transfer from the Re^I(CO)_3 unit to 5-NO_(2-)phen in these states. Transient visible absorption spectra indicate that the excited electron is delocalized over the 5-NO_(2-)phen ligand, which acquires radical anionic character. Similarly, involvement of the -NO_2 group in the Franck−Condon MLCT transition is manifested by the presence of an enhanced ν(NO_2) band in the preresonance Raman spectrum of [Re^I(4-Etpy)(CO)_3(5-NO_(2-)phen)]^+. The Re^I → 5-NO_(2-)phen ^3MLCT excited states are very short-lived:  7.6, 170, and 43 ps for L = Cl-, 4-Etpy, and imH, respectively, in CH_3CN solutions. The ^3MLCT excited state of [Re^I(imH)(CO)_3(5-NO_(2-)phen)]^+ is even shorter-lived in MeOH (15 ps) and H_2O (1.3 ps). In addition to ^3MLCT, excitation of [Re^I(imH)(CO)_3(5-NO_(2-)phen)]^+ populates a ^3LLCT (imH → 5-NO_(2-)phen) excited state. Most of the ^3LLCT population decays to the ground state (time constants of 19 (H_2O), 50 (MeOH), and 72 ps (CH_3CN)); in a small fraction, however, deprotonation of the imH^(•+) ligand occurs, producing a long-lived species, [Re^I(im^•)(CO)_3(5-NO_(2-)phen)^(•-)]^+.

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Gray, Harry B.0000-0002-7937-7876
Additional Information:© 2004 American Chemical Society. Received 20 December 2003. Published online 10 July 2004. Published in print 1 August 2004. Majid Motevalli (QMUL) determined the crystal structure of [Re^I(4-Etpy)(CO)_3(5-NO_(2-)phen)]PF_6. We thank Mona Shahgholi, David Jenkins, and Larry Henling for helpful discussions. Time-resolved visible absorption spectra were measured with the kind help of Mikhail Zimin and M. Groeneveld at the Institute of Molecular Chemistry, University of Amsterdam, The Netherlands. I. P. Clark assisted with resonance Raman experiments at the LSF Nanosecond Laboratory at RAL. This work was supported by the EPSRC, COST Action D14 European collaboration program and NIH (DK19038).
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Engineering and Physical Sciences Research Council (EPSRC)UNSPECIFIED
European CommissionCOST Action D14
Issue or Number:16
Record Number:CaltechAUTHORS:20170425-065431541
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Official Citation:Excited-State Dynamics of fac-[ReI(L)(CO)3(phen)]+ and fac-[ReI(L)(CO)3(5-NO2-phen)]+ (L = Imidazole, 4-Ethylpyridine; Phen = 1,10-Phenanthroline) Complexes Michael Busby, Anders Gabrielsson, Pavel Matousek, Michael Towrie, Angel J. Di Bilio, Harry B. Gray, and Antonín Vlček, Jr. Inorganic Chemistry 2004 43 (16), 4994-5002 DOI: 10.1021/ic035471b
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76893
Deposited By: Ruth Sustaita
Deposited On:25 Apr 2017 16:38
Last Modified:15 Nov 2021 17:03

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