肾上腺素是一种神经和激素的传送体, 研究肾上腺素分子的光谱和能级有助于了解其化学稳定性和药理作用。 基于密度泛函理论(DFT), 利用Gaussian 09软件在B3LYP/6-311G(d, p)基组水平上对肾上腺素分子进行结构优化, 采用含时密度泛函理论(TD-DFT)的PBE方法在def2tzvp基组水平上计算肾上腺素分子在气相中的前20个激发态, 利用Multiwfn3.7(dev)软件绘制出其紫外光谱图并对激发性质进行分析。 肾上腺素分子紫外光谱对应的主要跃迁是从基态分别到第1, 2, 4, 8, 15和16激发态的跃迁, 其他的激发态的振子强度低于阈值0.03。 理论计算得出肾上腺素的紫外光谱有两个吸收峰, 分别位于206.23和273.92 nm, 206.23 nm峰主要由基态跃迁到第16激发态形成, 273.92 nm峰主要是基态跃迁到第2、 4激发态形成, 主要是由苯环上π→π^*跃迁所产生, 并与实验光谱吻合较好。 对肾上腺素分子的激发态性质分析可知, 上述吸收峰都是在最高占据轨道和最低空轨道的临近轨道跃迁产生的。 利用密度泛函的PBE方法在6-311G(d, p)的基组水平上计算肾上腺素分子频率并绘制红外光谱, 由振动分析可知, 3 738和3 662 cm^-1峰是由酚羟基O—H伸缩振动产生的特征吸收峰, 3 715 cm^-1峰是由醇羟基O—H伸缩振动产生的特征吸收峰, 2 854 cm^-1峰是由甲基的C18—H20键的伸缩振动产生的特征吸收峰, 1 516和1 439 cm^-1峰是苯环骨架的伸缩振动的特征吸收峰, 1 279与1 057 cm^-1峰分别是由C6—O10和C12—O23键伸缩振动产生的特征吸收峰, 620 cm^-1峰是N22—H17键摇摆振动的特征吸收峰。 对比肾上腺素的实验红外光谱, 发现理论光谱与实验光谱中各基团的特征吸收峰都较为明显且总体吻合较好。 由于肾上腺素分子二聚体和多聚体之间形成氢键, 分子间氢键的形成削弱了O—H键的强度, 降低了能形成分子间氢键的羟基O—H的伸缩振动频率, 从而导致实验光谱在3 500~2 500 cm^-1之间呈现出一个宽峰。

Epinephrine is a neurotransmitter and hormone transmitter. Studying the spectra and energy levels of the epinephrine molecules may help to understand their chemical stability and pharmacological effects. Based on density functional theory (DFT), the structure of epinephrine was optimized by using Software Gaussian 09 at the level of B3LYP/6-311G(d, p) in this article. On this basis, the first 20 excited states of epinephrine molecule were calculated by using the time-dependent density functional theory (TD-DFT) at the level of PBE/def2tzvp in the gas phase, and ultraviolet spectrum was drawn by using Multiwfn3.7 (dev) software and the properties of excitation are analyzed. The main transitions corresponding to the UV spectrum of adrenaline molecules are those from the ground state to the first, second, fourth, eighth, 15th and 16th excited states respectively. The oscillator strength of other excited states is lower than the threshold value of 0.03. The theoretical calculation showed two absorption peaks in the ultraviolet spectrum of epinephrine, which are located at 206.23 and 273.92 nm respectively. The peak at 206.23 nm is mainly formed from the ground state transition to the 16th excited state, and the peak at 273.92 nm is mainly formed from the ground state transition to the 2nd and 4th excited states. They are mainly produced by the transition from π band to π^* band on the benzene ring, and they are in good agreement with the experimental spectrum. The analysis of the excited state properties of adrenergic molecules shows that the absorption peaks are generated in the adjacent orbital transitions of the highest occupied orbital and the lowest vacant orbital. Then, the PBE method based on density functional theory was used to calculate the infrared frequency and draw the infrared spectrum of adrenergic molecules at the base group level of 6-311g (d, p). The vibration analysis shows that the characteristic absorption peak is generated by the phenol hydroxyl O—H vibration at 3 738 and 3 662 cm^-1, and the alcohol hydroxyl O—H vibration generates the characteristic absorption peak at 3 715 cm^-1. Point 2 854 cm^-1 is the characteristic absorption peak generated by the stretching vibration of the C18—H20 bond of methyl, point 1 516 and 1 439 cm^-1 are the characteristic absorption peaks of the stretching vibration of the benzene ring, at 1 279 and 1 057 cm^-1 respectively were the characteristic absorption peak of the stretching vibration of the C6—O10 and C12—O23 bond, and point 620 cm^-1 is the characteristic absorption peak of the oscillation of the N22—H17 bond. The vibration analysis is consistent with the characteristic absorption peaks of various functional groups in the introduction to spectroscopy. By comparing the experimental infrared spectrum of epinephrine, it was found that the characteristic absorption peaks of each group in the theoretical spectrum were relatively obvious, and they were generally in good agreement with the experimental spectrum. Due to the hydrogen bond formed between the adrenergic molecular dimer and the polymer, the hydrogen bond formed between the molecules weakens the strength of the O—H bond. It reduces the stretching vibration frequency of the hydroxyl O—H that can form the inter-molecular hydrogen bond, which results in a wide peak of the experimental spectrum between 3 500 and 2 500 cm^-1.