Sanches de Araújo Adalberto V, Marques Leandro R, Borin Antonio C, Ando Rômulo A
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, Butantã 05508-000, São Paulo-SP, Brazil.
Phys Chem Chem Phys. 2022 Nov 30;24(46):28522-28529. doi: 10.1039/d2cp04401c.
Time-Dependent Density-Functional Theory (TDDFT) and Extended Multi-State Complete Active Space Second-Order Perturbation Theory (XMS-CASPT2) methods, together with augmented correlation-consistent polarizable valence double- (aug-cc-pVDZ) basis sets, were applied to simulate the vibronic and resonance Raman (RR) spectra of a push-pull model system, 4-nitroaniline (pNA) and its anion ([pNA]), within the Independent Mode Displaced Harmonic Oscillator (IMDHO) model. Both methods predict adequately well the vertical absorption spectra for both species and the well-known charge-transfer (CT; S11(ππ*)) excited state of pNA. Nevertheless, pNA and [pNA] absorption spectral band intensity and vibronic broadening are better reproduced at the XMS-CASPT2 level. RR spectra were also obtained using both methods, with a good agreement for both methods for pNA, for which the electronic wave functions are best described by a single state configuration. For the anion, for which the excited state presented a multiconfigurational nature, the TDDFT failed to predict the main intensification observed experimentally under resonance conditions. As to the resonance Raman excitation profile for the pNA species, the (NO) vibrational mode carries most of the intensity of the vibronic spectrum, but for [pNA] the contributions of main vibrational modes are more complex, being governed by different modes in different energies, with ring modes dominating at the maximum, as predicted by the XMS-CASPT2 method.
采用含时密度泛函理论（TDDFT）和扩展多态完全活性空间二阶微扰理论（XMS - CASPT2）方法，并结合增强相关一致极化价双ζ基组（aug - cc - pVDZ），在独立模式位移谐振子（IMDHO）模型下模拟了推挽模型体系4 - 硝基苯胺（pNA）及其阴离子（[pNA]）的电子振动光谱和共振拉曼（RR）光谱。两种方法都能较好地预测这两种物质的垂直吸收光谱以及pNA著名的电荷转移（CT；S11(ππ*)）激发态。然而，在XMS - CASPT2水平下，pNA和[pNA]的吸收光谱带强度和电子振动展宽能得到更好的再现。两种方法也都获得了RR光谱，对于pNA，两种方法的结果吻合良好，其电子波函数可用单态构型很好地描述。对于阴离子，其激发态具有多构型性质，TDDFT无法预测在共振条件下实验观察到的主要增强现象。至于pNA物种的共振拉曼激发轮廓，（NO）振动模式在电子振动光谱中贡献了大部分强度，但对于[pNA]，主要振动模式的贡献更为复杂，在不同能量下由不同模式主导，如XMS - CASPT2方法所预测的，在最大值处环模式占主导。
