期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 114, 期 46, 页码 12129-12137出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp104692w
关键词
-
资金
- Fundacao de Amparo a Pesquisa de So Paulo, FAPESP
- Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior, CAPES
- U.S. Department of Energy [DE-FG02-06ER15788]
- U.S. Department of Energy (DOE) [DE-FG02-06ER15788] Funding Source: U.S. Department of Energy (DOE)
Excited-state dynamics in fac-[Re(CO)(3)(Me(4)phen)(cis-L)](+) (Me(4)phen = 3,4,7,8-tetramethyl-1,10-phenanthroline, L = 4-styrylpyridine (stpy) or 1,2-bis(4-pyridyl)ethylene (bpe)) were investigated by steady-state and time-resolved techniques. A complex equilibrium among three closely lying excited states, 3IL(cis-L), (MLCTRe -> me4phen)-M-3, and (ILMe4phen)-I-3, has been established. Under UV irradiation, cis-to-trans isomerization of coordinated cis-L is observed with a quantum yield of 0.15 in acetonitrile solutions. This photoreaction competes with radiative decay from (MLCTRe -> Me4phen)-M-3 and (ILMe4phen)-I-3 excited states, leading to a decrease in the emission quantum yield relative to the nonisomerizable complex fac-[Re(CO)(3)(Me(4)phen)(bpa)](+) (bpa = 1,2-bis(4-pyridyl)ethane). From temperature-dependent time-resolved emission measurements in solution and in poly(methyl methacrylate) (PMMA) films, energy barriers (Delta E-a) for interconversion between (MLCTRe -> me4Phen)-M-3 and (ILMe4phen)-I-3 emitting states were determined. For L = cis-stpy, Delta E-a = 11 (920 cm(-1)) and 15 kJ mol(-1) (1254 cm(-1)) in 5:4 propionitrile/butyronitrile and PMMA, respectively. For L = cis-bpe, Delta E-a = 13 kJ mol(-1) (1087 cm(-1)) in 5:4 propionitrile/butyronitrile. These energy barriers are sufficient to decrease the rate constant for internal conversion from higher-lying (ILme4phen)-I-3 state to (MLCTRe -> Me4phen)-M-3, k(i) congruent to 10(6) s(-1). The decrease in rate allows for the observation of intraligand phosphorescence, even in fluid medium at room temperature. Our results provide additional insight into the role of energy gap and excited-state dynamics on the photochemical and photophysical properties of Re(I) polypyridyl complexes.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据