Stockett M H, Brøndsted Nielsen S
Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark.
J Chem Phys. 2015 May 7;142(17):171102. doi: 10.1063/1.4919781.
Tris(bipyridine)ruthenium(II) (Ru(bipy)3 (2+)) is a prototypical transition metal coordination complex whose photophysical properties have attracted considerable attention. A much debated issue is whether the metal-to-ligand charge transfer (MLCT) transition that accounts for the complex's beautiful red color is fully delocalized across all three bipyridine ligands or located on just one ligand. Here, we show based on gas-phase action spectroscopy that attachment of a single acetonitrile molecule does not change the absorption spectrum from that of the bare ions, which is indicative of a delocalized state. However, the gas-phase spectra of the bare and one solvent molecule complexes are significantly blueshifted relative to that obtained in bulk acetonitrile, which suggests that in solution the polarizability of many solvent molecules working together can localize the MLCT state. Our data clearly show that more than one solvent molecule is needed to break the symmetry of the MLCT excited state and reproduce its solution-phase characteristics.
三联吡啶钌（II）（Ru(bipy)3 (2+)）是一种典型的过渡金属配位络合物，其光物理性质备受关注。一个备受争议的问题是，赋予该络合物美丽红色的金属到配体的电荷转移（MLCT）跃迁是完全离域在所有三个联吡啶配体上，还是仅位于一个配体上。在此，我们基于气相作用光谱表明，单个乙腈分子的附着并不会改变裸离子的吸收光谱，这表明是离域态。然而，裸离子和一个溶剂分子络合物的气相光谱相对于在乙腈本体中获得的光谱显著蓝移，这表明在溶液中，许多共同作用的溶剂分子的极化率可以使MLCT态局域化。我们的数据清楚地表明，需要不止一个溶剂分子来打破MLCT激发态的对称性并重现其溶液相特征。
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