Excited-State Dynamics of fac-[ReI(L)(CO)3(phen)]+ and fac-[ReI(L)(CO)3(5-NO2-phen)]+ (L = Imidazole, 4-Ethyl
详细信息 查看全文
- 作者：Michael Busby ; Anders Gabrielsson ; Pavel Matousek ; Michael Towrie ; Angel J. Di Bilio ; Harry B. Gray ; and Antoní ; n Vl
//pubs.acs.org/images/entities/ccaron.gif" border="0">ek ; Jr.
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：August 9, 2004
- 年：2004
- 卷：43
- 期：16
- 页码：4994 - 5002
- 全文大小：272K
- 年卷期：v.43,no.16(August 9, 2004)
- ISSN：1520-510X
文摘
The nature and dynamics of the lowest excited states of fac-[ReI(L)(CO)3(phen)]+ and fac-[ReI(L)(CO)3(5-NO2-phen)]+ [L = Cl-, 4-ethyl-pyridine (4-Etpy), imidazole (imH); phen = 1,10-phenanthroline] have been investigatedby 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 ReI 
phen 3MLCT excited states,characterized by CO stretching frequencies that are upshifted relative to their ground-state values and by widelysplit IR bands due to the out-of-phase A'(2) and A' ' 
(CO) vibrations. The lowest excited states of the 5-NO2-phencomplexes also have 3MLCT character; the larger upward (CO) shifts accord with much more extensive chargetransfer from the ReI(CO)3 unit to 5-NO2-phen in these states. Transient visible absorption spectra indicate that theexcited electron is delocalized over the 5-NO2-phen ligand, which acquires radical anionic character. Similarly,involvement of the -NO2 group in the Franck-Condon MLCT transition is manifested by the presence of an enhanced(NO2) band in the preresonance Raman spectrum of [ReI(4-Etpy)(CO)3(5-NO2-phen)]+. The ReI 5-NO2-phen3MLCT excited states are very short-lived: 7.6, 170, and 43 ps for L = Cl-, 4-Etpy, and imH, respectively, inCH3CN solutions. The 3MLCT excited state of [ReI(imH)(CO)3(5-NO2-phen)]+ is even shorter-lived in MeOH (15 ps)and H2O (1.3 ps). In addition to 3MLCT, excitation of [ReI(imH)(CO)3(5-NO2-phen)]+ populates a 3LLCT (imH 5-NO2-phen) excited state. Most of the 3LLCT population decays to the ground state (time constants of 19 (H2O),50 (MeOH), and 72 ps (CH3CN)); in a small fraction, however, deprotonation of the imH
+ ligand occurs, producinga long-lived species, [ReI(im)(CO)3(5-NO2-phen)-]+.
phen 3MLCT excited states,characterized by CO stretching frequencies that are upshifted relative to their ground-state values and by widelysplit IR bands due to the out-of-phase A'(2) and A' ' (CO) vibrations. The lowest excited states of the 5-NO2-phencomplexes also have 3MLCT character; the larger upward (CO) shifts accord with much more extensive chargetransfer from the ReI(CO)3 unit to 5-NO2-phen in these states. Transient visible absorption spectra indicate that theexcited electron is delocalized over the 5-NO2-phen ligand, which acquires radical anionic character. Similarly,involvement of the -NO2 group in the Franck-Condon MLCT transition is manifested by the presence of an enhanced(NO2) band in the preresonance Raman spectrum of [ReI(4-Etpy)(CO)3(5-NO2-phen)]+. The ReI 5-NO2-phen3MLCT excited states are very short-lived: 7.6, 170, and 43 ps for L = Cl-, 4-Etpy, and imH, respectively, inCH3CN solutions. The 3MLCT excited state of [ReI(imH)(CO)3(5-NO2-phen)]+ is even shorter-lived in MeOH (15 ps)and H2O (1.3 ps). In addition to 3MLCT, excitation of [ReI(imH)(CO)3(5-NO2-phen)]+ populates a 3LLCT (imH 5-NO2-phen) excited state. Most of the 3LLCT population decays to the ground state (time constants of 19 (H2O),50 (MeOH), and 72 ps (CH3CN)); in a small fraction, however, deprotonation of the imH+ ligand occurs, producinga long-lived species, [ReI(im)(CO)3(5-NO2-phen)-]+.