Hou Xin-Juan, Quan Phung, Höltzl Tibor, Veszprémi Tamas, Nguyen Minh Tho
Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
J Phys Chem A. 2005 Nov 17;109(45):10396-402. doi: 10.1021/jp0533527.
Multireference complete active space self-consistent-field CASSCF(10,12)/ANO and second-order perturbation theory MS-CASPT2 calculations were performed to determine the vertical low-lying singlet and triplet states of aniline. The sequence of the seven lower lying triplet states is T1(1(3)A'), T2(1(3)A' '), T3(2(3)A'), T4(3(3)A'), T5(2(3)A' '), T6(4(3)A'), and T7(3(3)A' '). The 3(3)A', 4(3)A', and 3(3)A' ' states are assigned as 3s, 3py, and 3pz Rydberg states, respectively, while other states correspond to pi <-- pi excitations. Both the T1 and T2 states are found to be below at the lowest-lying singlet S1 (1(1)A' ') state. Geometry, vibrational modes, and electron distribution of the lowest lying T1 state were determined using UB3LYP calculations. The vertical and adiabatic singlet-triplet energy gaps DeltaE(S0-T1) amount to 3.7 and 3.5 +/- 0.2 eV, respectively. In clear contrast with the S0 state, the triplet aniline is no longer aromatic, and its protonation occurs preferentially at the ring meta-carbon site, with a proton affinity PA = 243 +/- 3 kcal/mol.
进行了多参考完全活性空间自洽场CASSCF(10,12)/ANO和二阶微扰理论MS-CASPT2计算，以确定苯胺的垂直低能单重态和三重态。七个较低能三重态的顺序为T1(1(3)A')、T2(1(3)A'')、T3(2(3)A')、T4(3(3)A')、T5(2(3)A'')、T6(4(3)A')和T7(3(3)A'')。3(3)A'、4(3)A'和3(3)A''态分别被指定为3s、3py和3pz里德堡态，而其他态对应于π←π激发。发现T1和T2态都低于最低单重态S1(1(1)A'')态。使用UB3LYP计算确定了最低能T1态的几何结构、振动模式和电子分布。垂直和绝热单重态-三重态能隙ΔE(S0-T1)分别为3.7和3.5±0.2 eV。与S0态形成鲜明对比的是，三重态苯胺不再具有芳香性，其质子化优先发生在环间位碳位点，质子亲和能PA = 243±3 kcal/mol。
