Vibrational relaxation of CN stretch of pseudo-halide anions (OCN -, SCN-, and SeCN-) in polar solvents

被引：56
作者：
Department of Chemistry, Emory University, Atlanta, GA 30322, United States [1 ]
机构：
[1] Department of Chemistry, Emory University, Atlanta
来源：
J Phys Chem B | 2006年 / 40卷 / 19990-19997期
关键词：
Energy transfer - Ground state - Infrared spectroscopy - Ion sources - Isotopes - Molecular dynamics - Relaxation processes;
D O I：
10.1021/jp0623261
中图分类号：
学科分类号：
摘要：
The vibrational relaxation dynamics of pseudo-halide anions XCN- (X=O, S, Se) in polar solvents were studied to understand the effect of charge on solute-to-solvent intermolecular energy transfer (IET) and solvent assisted intramolecular vibrational relaxation (IVR) pathways. The T1 relaxation times of the CN stretch in these anions were measured by IR pump/IR probe spectroscopy, in which the 0-1 transition was excited, and the 0 - 1 and 1 - 2 transitions were monitored to follow the recovery of the ground state and decay of the excited state. For these anions in five solvents, H2O, D2O, CH3OH, CH3CN, and (CH3) 2SO, relaxation rates followed the trend of OCN- > SCN- > SeCN-. For these anions and isotopes of SCN -, the relaxation rate was a factor of a few (2.5-10) higher in H2O than in D2O. To further probe the solvent isotope effect, the relaxation rates of S12C14N-, S13C14N-, and S12C 15N- in deuterated methanols (CH3OH, CH 3OD, CH3OH, CD3OD) were compared. Relaxation rate was found to be affected by the change of solvent vibrational band at the CN- stretching mode (CD3 symmetric stretch) and lower frequency regions, suggesting the presence of both direct IET and solvent assisted IVR relaxation pathways. The possible relaxation pathways and mechanisms for the observed trends in solute and solvent dependence were discussed. © 2006 American Chemical Society.
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页码：19990 / 19997
页数：7
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