Waterland Mark R, Howell Sarah L, Gordon Keith C
Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
J Phys Chem A. 2007 May 31;111(21):4604-11. doi: 10.1021/jp070389d. Epub 2007 May 9.
A resonance Raman intensity analysis of the metal-to-ligand charge-transfer (MLCT) transition for the rhenium compound Re(2-(2'-pyridyl)quinoxaline)(CO)(3)Cl (RePQX) is presented. Photoinduced geometry changes are calculated, and the results are presented using the vibrational normal modes and the redundant internal coordinates. A density functional theory calculation is used to determine the ground-state nonresonant Raman spectrum and a transformation matrix that transforms the redundant internal coordinates into the normal modes. The normal modes nu(37) (rhenium coordination sphere distortion) and nu(75) (ligand skeletal stretch) show the largest photoinduced geometry change (Delta = 1.0 and 0.7, respectively). A single carbonyl mode is enhanced in the resonance Raman spectra. Time-dependent density functional theory is used to calculate excited-state geometry changes, which are subsequently used to determine the signs of the photoinduced normal mode displacements. Transforming to internal coordinates reveals that all the CO bond lengths are displaced in the excited state. The Re-C and C-C ligand bond lengths are also displaced in the excited state. The results are discussed in terms of a simple one-electron picture for the electronic transition. Many bond angles and torsional coordinates are also displaced by the metal-to-ligand charge transfer, and most of these are associated with the rhenium coordination sphere. It is demonstrated that using internal coordinates presents a clear picture of the geometry changes associated with photoinduced electron transfer in metal polypyridyl systems.
本文对铼化合物Re(2-(2'-吡啶基)喹喔啉)(CO)(3)Cl（RePQX）的金属到配体电荷转移（MLCT）跃迁进行了共振拉曼强度分析。计算了光诱导的几何结构变化，并使用振动正则模式和冗余内坐标展示了结果。利用密度泛函理论计算确定基态非共振拉曼光谱以及将冗余内坐标转换为正则模式的变换矩阵。正则模式ν(37)（铼配位球畸变）和ν(75)（配体骨架伸缩）显示出最大的光诱导几何结构变化（分别为Δ = 1.0和0.7）。在共振拉曼光谱中，单个羰基模式增强。使用含时密度泛函理论计算激发态几何结构变化，随后用于确定光诱导正则模式位移的符号。转换为内坐标表明，在激发态下所有CO键长均发生位移。Re-C和C-C配体键长在激发态下也发生位移。根据电子跃迁的简单单电子图像对结果进行了讨论。许多键角和扭转坐标也因金属到配体的电荷转移而发生位移，其中大部分与铼配位球相关。结果表明，使用内坐标清晰地展现了金属多吡啶体系中与光诱导电子转移相关的几何结构变化。
