Leśniewski Sebastian, Kolek Przemyslaw, Pirowska Katarzyna, Sobolewski Andrzej L, Najbar Jan
Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, 3 Ingardena, PL-30-060 Cracow, Poland.
J Chem Phys. 2009 Feb 7;130(5):054307. doi: 10.1063/1.3043818.
Geometry and vibrational modes of the anthranilic acid molecule in the S(0) and S(1) states were computed using ab initio methods: Hartree-Fock (HF) and configuration interaction of singly excited configurations (CIS) as well as the density functional theory with time-dependent perturbation (TD-DFT). The intensity distribution in the laser-induced fluorescence excitation spectra was modeled in two ways: using displacement parameters for independent modes and using multidimensional Franck-Condon integrals. The change in the molecular geometry upon excitation was calculated from the band intensities within the above two models. Displacement parameters of eight in-plane modes active in the excitation spectrum were optimized to reproduce the experimental intensities of about 40 most intensive and well-separated vibrational bands, while displacement parameters of other in-plane modes were kept frozen at the values resulting from the quantum chemical calculations. The intramolecular hydrogen bond is significantly stronger in the S(1) state than in the ground state. Additionally, bond lengths and angles in the aromatic ring, within the substituents and between the ring and the substituents undergo significant changes and they induce the presence of strong fundamentals in the excitation spectrum.
采用从头算方法计算了邻氨基苯甲酸分子在S(0)和S(1)态的几何结构和振动模式：包括哈特里-福克（HF）方法、单激发组态相互作用（CIS）以及含时密度泛函理论（TD-DFT）。激光诱导荧光激发光谱中的强度分布通过两种方式进行建模：使用独立模式的位移参数和使用多维弗兰克-康登积分。根据上述两种模型中的谱带强度计算激发时分子几何结构的变化。优化了激发光谱中八个平面内活性模式的位移参数，以重现约40个最强且分离良好的振动谱带的实验强度，而其他平面内模式的位移参数则保持在量子化学计算得出的值不变。分子内氢键在S(1)态比基态显著更强。此外，芳环内、取代基内以及环与取代基之间的键长和键角发生了显著变化，这导致激发光谱中出现强的基频峰。
