The vibronic absorption spectrum of Azure B (AB) in an aqueous solution is calculated using the time-dependent density functional theory (TD-DFT). The results of calculations are analyzed using all hybrid functionals supported by Gaussian16, the 6-31++G(d,p) basis set, and the IEFPCM and SMD solvent models. The solvent model IEFPCM gave significantly underestimated values of λ_max in comparison with the experiment. This is a manifestation of the TD-DFT “cyanine failure”. However, the SMD model made it possible to obtain good agreement between the calculation results and experimental data. The best fit was achieved using the X3LYP functional. According to our calculations, the shoulder in the visible absorption spectrum of AB has a vibronic origin. However, the calculated shoulder is weaker than the experimental one. Explicit assignment of two water molecules, which form strong hydrogen bonds with a dye molecule, leads to a shift of the calculated absorption spectrum to longer wavelengths by approximately 17 nm but does not lead to an improvement in its shape. Comparative analysis of the calculated vibronic absorption spectra of Azure B with those obtained earlier for Azure A and methylene blue showed that the presence and intensity of the short-wavelength shoulder are determined by the location of the bands of higher vibronic transitions relative to the band of the 0₀ → 0⁰ main transitions. Photoexcitation leads to an increase in the dipole moment of the dye molecule. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule.

使用瞬态密度泛函理论 (TD-DFT) 计算 Azure B (AB) 在水溶液中的振动吸收光谱。使用 Gaussian16 支持的所有混合泛函、6-31++G(d,p) 基组以及 IEFPCM 和 SMD 溶剂模型分析计算结果。溶剂模型 IEFPCM 给出了显着低估的λ _{max 值}与实验相比。这是TD-DFT“花青失效”的一种表现。然而，SMD 模型使得计算结果和实验数据之间获得良好的一致性成为可能。使用 X3LYP 泛函实现了最佳拟合。根据我们的计算，AB 的可见吸收光谱中的肩部具有振动起源。然而，计算的肩比实验的要弱。与染料分子形成强氢键的两个水分子的显式分配导致计算的吸收光谱向更长的波长移动约 17 nm，但不会导致其形状的改善。₀  → 0 ⁰主要转换。光激发导致染料分子偶极矩的增加。在染料分子发色团的中心环中发现了微不足道的光致电子转移。