Theoretical Study of the Electronic Spectrum of Imidazole
Theoretical Study of the Electronic Spectrum of Imidazole
复制标题
咪唑电子能谱的理论研究
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
M. Merchán
中科院分区：
文献类型：
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作者：
L. Serrano;M. Fülscher;B. Roos;M. Merchán
采用完整活性空间（CAS）自洽场（SCF）方法和多参考二阶微扰理论（CASPT2）研究了咪唑和咪唑鎓离子的电子能谱。计算包括大量的单重态和三重态、价态和里德伯激发态。新开发的连续体模型已用于计算溶剂化变色位移。在气相中，咪唑的第一和第二 π → π* 激发单线态价态计算为 6.72 和 7.15 eV，并在溶剂化后转变为 6.32 和 6.53 eV。由于 CASSCF 波函数中错误的价-里德堡混合，气相值有点太大（约 0.3 eV）。咪唑鎓离子的第一和第二 π → π* 激发单线态价态在气相中计算为 5.72 和 6.94 eV，在水溶液中转变为 5.86 和 6.83 eV。目前的结果与在水溶液中观察到的吸收带最大值一致，咪唑和...的吸收带最大值为 6.0 和 6.5 eV。
The complete active space (CAS) self-consistent field (SCF) method and multireference second-order perturbation theory (CASPT2) have been used to study the electronic spectrum of imidazole and the imidazolium ion. The calculations comprise a large number of, both singlet and triplet, valence and Rydberg excited states. A newly developed continuum model has been used to compute solvatochromic shifts. In the gas phase the first and second π → π* excited singlet valence states of imidazole are computed at 6.72 and 7.15 eV, and they shift to 6.32 and 6.53 eV upon solvation. The gas-phase values are somewhat too large (≈0.3 eV) due to an erroneous valence−Rydberg mixing in the CASSCF wave function. The first and second π → π* excited singlet valence states of the imidazolium ion are computed at 5.72 and 6.94 eV in the gas phase and shifted to 5.86 and 6.83 eV in aqueous solutions. The present results are in agreement with the observed absorption band maxima in aqueous solution, 6.0 and 6.5 eV for imidazole and...