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The effect of solute-solvent interaction on the radiationless relaxation rate of the ^3MLCT states of tris(alpha, alpha'-diimine)metal(II) complexes

溶质-溶剂相互作用对三(α,α-二亚胺)金属(II)配合物^3MLCT态无辐射弛豫率的影响

基本信息

批准号：
07404036
负责人：
KAIZU Youkoh
金额：
$ 18.3万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

The radiationless decay rates of Ru(bpy)_3^<2+>, Ru(phen)_3^<2+> Os(bpy)_3^<2+> and Os(phen)_3^<2+> were measured in water-alcohol and -dioxane mixted solvents. In the Ru(II) complexes, we divided the radiationless decay rate into two non-radiative processes from the results of the measurements for the temperature dependence : one is the path to the ground state directly (IC path) and another is the path to the metal center state above the ^3MLCT state (MC path). On the contrary, the IC path is predominant in Os(II) complexes. By using the deuterated solvent, it has been revealed that no isotope effect is observed in the MC path. For the IC path, a large isotope effect on the rate was observed in water while a slight isotope effect was observed in alcohol. On adding alcohol to water, the rate constant decreased nonlinearly With increase of mole fraction of alcohol. In order to explain the observed solvent effect on the rates, we proposed a new model for the radiationless transition to … More the ground state as below instead of the mechanism of charge-transfer-to-solvent : the water molecule included between ligands of the complex may accept the excitation energy followed by the energy dissipation toward the cluster of outer sorrounding solvents with which the included water combines in advance. The interaction between the included solvent and the ligands varies accompanying with the change in the interaction between the included solvent and the outer solvent cluster. Therefore, the transmission coefficient, kappa, of the energy tranefer from the metal complex to the included water molecule is change with the microscopic structure of solvent, since the interaction between the included solvent and the outer solvent cluster is changed by the strength of the hydrogen bond of the outer cluster. In alcohol, since the included alcohol molecule have only one OH,the molecule must reorientate to dissipate the excitation energy to the outer solvent cluster. Thus the kappa should be small. Less

本文报道了Ru（bpy）_3^<2+>、Ru（phen）_3^<2+>、Os（bpy）_3 ^<2+>和Os（phen）_3^<2+>在水-乙醇和二氧六环混合溶剂中的无辐射衰变速率。在Ru（II）配合物中，我们根据温度依赖性的测量结果，将无辐射衰减速率分为两个无辐射过程：一个是直接到达基态的路径（IC路径），另一个是到达^3MLCT态以上的金属中心态的路径（MC路径）。相反，IC路径在Os（II）配合物中占主导地位。结果表明，在氘代溶剂中，MC路径不存在同位素效应，IC路径在水溶液中存在较大的同位素效应，而在乙醇溶液中存在较小的同位素效应。在水溶液中加入乙醇时，反应速率常数随乙醇摩尔分数的增加呈非线性下降。为了解释所观察到的溶剂效应，我们提出了一个新的无辐射跃迁模型， ...更多信息基态如下，而不是电荷转移到溶剂的机制：包括在络合物的配体之间的水分子可以接受激发能量，随后能量耗散到外部周围溶剂的簇，所包括的水预先与所述簇结合。所包含的溶剂和配体之间的相互作用随着所包含的溶剂和外部溶剂簇之间的相互作用的变化而变化。因此，从金属络合物到所包含的水分子的能量转移的透射系数kappa随着溶剂的微观结构而改变，因为所包含的溶剂与外部溶剂簇之间的相互作用通过外部簇的氢键强度而改变。在醇中，由于所包含的醇分子只有一个OH，分子必须重新取向以将激发能耗散到外部溶剂簇。因此，Kappa应该是小的。少