Using Internal Coordinates to Describe Photoinduced Geometry Changes in MLCT Excited States
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- 作者：Mark R. Waterland ; Sarah L. Howell ; Keith C. Gordon
- 刊名：Journal of Physical Chemistry A
- 出版年：2007
- 出版时间：May 31, 2007
- 年：2007
- 卷：111
- 期：21
- 页码：4604 - 4611
- 全文大小：261K
- 年卷期：v.111,no.21(May 31, 2007)
- ISSN：1520-5215
文摘
A resonance Raman intensity analysis of the metal-to-ligand charge-transfer (MLCT) transition for the rheniumcompound Re(2-(2'-pyridyl)quinoxaline)(CO)3Cl (RePQX) is presented. Photoinduced geometry changes arecalculated, and the results are presented using the vibrational normal modes and the redundant internalcoordinates. A density functional theory calculation is used to determine the ground-state nonresonant Ramanspectrum and a transformation matrix that transforms the redundant internal coordinates into the normal modes.The normal modes 
37 (rhenium coordination sphere distortion) and 75 (ligand skeletal stretch) show thelargest photoinduced geometry change (
= 1.0 and 0.7, respectively). A single carbonyl mode is enhancedin the resonance Raman spectra. Time-dependent density functional theory is used to calculate excited-stategeometry changes, which are subsequently used to determine the signs of the photoinduced normal modedisplacements. Transforming to internal coordinates reveals that all the CO bond lengths are displaced in theexcited state. The Re-C and C-C ligand bond lengths are also displaced in the excited state. The results arediscussed in terms of a simple one-electron picture for the electronic transition. Many bond angles and torsionalcoordinates are also displaced by the metal-to-ligand charge transfer, and most of these are associated withthe rhenium coordination sphere. It is demonstrated that using internal coordinates presents a clear picture ofthe geometry changes associated with photoinduced electron transfer in metal polypyridyl systems.
37 (rhenium coordination sphere distortion) and 75 (ligand skeletal stretch) show thelargest photoinduced geometry change ( = 1.0 and 0.7, respectively). A single carbonyl mode is enhancedin the resonance Raman spectra. Time-dependent density functional theory is used to calculate excited-stategeometry changes, which are subsequently used to determine the signs of the photoinduced normal modedisplacements. Transforming to internal coordinates reveals that all the CO bond lengths are displaced in theexcited state. The Re-C and C-C ligand bond lengths are also displaced in the excited state. The results arediscussed in terms of a simple one-electron picture for the electronic transition. Many bond angles and torsionalcoordinates are also displaced by the metal-to-ligand charge transfer, and most of these are associated withthe rhenium coordination sphere. It is demonstrated that using internal coordinates presents a clear picture ofthe geometry changes associated with photoinduced electron transfer in metal polypyridyl systems.