Computational Modeling of the Triplet Metal-to-Ligand Charge-Transfer Excited-State Structures of Mono-Bipyridine鈥揜uthenium(II) Complexes and Comparisons to their 77 K Emission Band Shapes

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• 作者：Richard L. Lord ; Marco M. Allard ; Ryan A. Thomas ; Onduro S. Odongo ; H. Bernhard Schlegel ; Yuan-Jang Chen ; John F. Endicott
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：February 4, 2013
• 年：2013
• 卷：52
• 期：3
• 页码：1185-1198
• 全文大小：772K
• 年卷期：v.52,no.3(February 4, 2013)
• ISSN：1520-510X

文摘

A computational approach for calculating the distortions in the lowest energy triplet metal to ligand charge-transfer (³MLCT = T₀) excited states of ruthenium(II)鈥揵ipyridine (Ru鈥揵py) complexes is used to account for the patterns of large variations in vibronic sideband amplitudes found in the experimental 77 K emission spectra of complexes with different ancillary ligands (L). Monobipyridine, [Ru(L)₄bpy]^m+ complexes are targeted to simplify analysis. The range of known emission energies for this class of complexes is expanded with the 77 K spectra of the complexes with (L)₄ = bis-acetonylacetonate (emission onset at about 12鈥?00 cm^鈥?) and 1,4,8,11-tetrathiacyclotetradecane and tetrakis-acetonitrile (emission onsets at about 21鈥?00 cm^鈥?); no vibronic sidebands are resolved for the first of these, but they dominate the spectra of the last two. The computational modeling of excited-state distortions within a Franck鈥揅ondon approximation indicates that there are more than a dozen important distortion modes including metal鈥搇igand modes (low frequency; lf) as well as predominately bpy modes (medium frequency; mf), and it simulates the observed 77 K emission spectral band shapes of selected complexes very well. This modeling shows that the relative importance of the mf modes increases very strongly as the T₀ energy increases. Furthermore, the calculated metal-centered SOMOs show a substantial bpy鈭捪€-orbital contribution for the complexes with the highest energy T₀. These features are attributed to configurational mixing between the diabatic MLCT and the bpy ³蟺蟺* excited states at the highest T₀ energies.