Ultrafast Dynamics of the Low-Lying 3MLCT States of [Ru(bpy)2(dppp2)]2+

详细信息    查看全文

• 作者：Yujie Sun ; Yao Liu ; Claudia Turro
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：April 28, 2010
• 年：2010
• 卷：132
• 期：16
• 页码：5594-5595
• 全文大小：147K
• 年卷期：v.132,no.16(April 28, 2010)
• ISSN：1520-5126

文摘

The solvent dependence of the excited state dynamics of [Ru(bpy)₂(dppp2)]²⁺ (bpy = 2,2′-bipyridine, dppp2 = pyrido[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline) were investigated using ultrafast transient absorption spectroscopy. In contrast to the “DNA light-switch” complex [Ru(bpy)₂(dppz)]²⁺ (dppz = dipyrido[3,2-a:2′,3′-c]phenzine), the structurally related [Ru(bpy)₂(dppp2)]²⁺ exhibits discrete formation of the lowest-lying ³MLCT^dis (MLCT = metal-to-ligand charge transfer) state from the higher-energy ³MLCT^prox state in the picosecond time scale. In ³MLCT^dis and ³MLCT^prox, the transferred electron is localized on the portion of the dppp2 ligand distal and proximal to the metal, respectively. The greater dipole moment of ³MLCT^dis compared to ³MCLT^prox, together with the ability of the dppp2 ligand to hydrogen bond, results in a strong dependence of the kinetics of the interconversion process on solvent polarity, decreasing from 67 to 26 ps in CH₂Cl₂ and CH₃CN, respectively. Similarly, the lifetime of the emission of the lowest energy state of [Ru(bpy)₂(dppp2)]²⁺ also decreases from 273 to 35 ns in the same solvents. In CH₃CH₂OH, both the rate of interconversion and the decay of ³MLCT^dis are significantly faster, 6.7 ps and 1.7 ns, respectively. Such dependence of the excited state properties is not observed for [Ru(bpy)₂(dppz)]²⁺. The results are consistent with the relative stabilization of ³MLCT^dis of the dppp2 complex in CH₃CN compared to CH₂Cl₂ due to solvent polarity, which may be further stabilized by hydrogen bonding in CH₃CH₂OH.