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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >A First-Principles Approach to the Dynamics and Electronic Properties of p-Nitroaniline in Water
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A First-Principles Approach to the Dynamics and Electronic Properties of p-Nitroaniline in Water

机译：水中对硝基苯胺动力学和电子性质的第一性原理

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摘要

Born-Oppenheimer molecular dynamics of p-nitro aniline (PNA) in water was carried out and the electronic structure was investigated by time-dependent density functional theory. Hydrogen bonding involving the PNA nitro and amine groups and the water molecules leads to an similar to 160 cm(-1) red shift of the nu(N-O) and v(N H) stretching frequencies relative to the gas phase species. Our estimate for the peak position of the charge transfer (CT) band in the absorption spectrum of PNA in water (similar to 3.5 eV) is in good agreement with experimental data (3.3 eV). We have investigated the specific role played by local hydrogen bonding and electrostatic interactions on the electronic absorption spectrum. It is shown that although electrostatic interactions play a major role for explaining the structure of the PNA CT band in water, the theoretical prediction of the observed red shift is improved by the explicit consideration of local hydrogen bonding of PNA to water. For isolated PNA, we predict that the dipole moment of the second excited state (S-2) is 9.6 D greater than ground state (S-0) dipole, which is in good agreement with experimental information (8.2-9.3 D). Calculation of charge transfer indexes for the two first excitations of PNA in water indicates that despite the-feature that a small fraction of Si states (<5%) may exhibit some CT character, CT states in solution are mainly associated with S-2 <- S-0 transitions.
机译：进行了对硝基苯胺（PNA）在水中的Born-Oppenheimer分子动力学研究，并通过时变密度泛函理论研究了电子结构。氢键涉及PNA的硝基和胺基以及水分子，导致nu（N-O）和v（NH）拉伸频率相对于气相物质的类似于160 cm（-1）的红移。我们对水中PNA吸收光谱中电荷转移（CT）谱带的峰值位置的估计（类似于3.5 eV）与实验数据（3.3 eV）非常吻合。我们已经研究了局部氢键和电子吸收光谱上的静电相互作用所起的特定作用。结果表明，尽管静电相互作用在解释水中PNA CT谱带的结构中起主要作用，但通过明确考虑PNA与水之间的局部氢键，可以改善理论上对观测到的红移的预测。对于隔离的PNA，我们预测第二个激发态（S-2）的偶极矩比基态（S-0）偶极大9.6 D，这与实验信息（8.2-9.3 D）很好地吻合。水中PNA的两个首次激发的电荷转移指数的计算表明，尽管具有少量Si状态（<5％）可能具有某些CT特性的特征，但溶液中的CT状态主要与S-2 < -S-0转换。

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