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首页> 外文期刊>Journal of structural chemistry >Quantum chemical and experimental studies on the structure and vibrational spectra of substituted 2-pyranones
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Quantum chemical and experimental studies on the structure and vibrational spectra of substituted 2-pyranones

机译：取代的2-吡喃酮的结构和振动光谱的量子化学和实验研究

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A systematic study on the structural characteristics of the 2-pyranone ring containing molecules with bromine, nitrile, and amide substituents at the C-3 position in the ring is conducted in the electronic ground (S 0) state by DFT calculations using the B3LYP/6-311++G** method. The geometrical structure of the bromine substituted compound, which shows potent hepatoprotective activity, is studied both in the ground (S 0) and first excited singlet (S 1) states using RHF/6-311++G** and CIS/6-311++G** methods respectively. The molecules are found to exist in two isomeric forms gauche and trans that have the enthalpy difference of less than 3.32 kcal/mol; the latter is the preferred orientation in the gaseous phase. The S_1 state is a ~1(π,π*) state that arises π-electron transfer from the region of a double bond in the pyranone ring to the region of the internuclear bond connecting the 2-pyranone and benzene rings. A complete vibrational analysis is conducted for the 3-bromo-6-(4-chlorophenyl)-4-thiomethyl-2H-pyran-2-one molecule based on the experimental infrared spectra in the 50-4000 cm~(?1) region and DFT/6- 311++G** computations of vibrational frequencies for the gauche and trans isomeric forms. Spectral assignments based on the potential energy distribution along the internal coordinates confirm the nonplanar structure of the molecule.
机译：使用B3LYP /，通过DFT计算，以电子基（S 0）态对环中C-3位置具有溴，腈和酰胺取代基的2-吡喃酮环的分子的结构特征进行了系统研究。 6-311 ++ G **方法。使用RHF / 6-311 ++ G **和CIS / 6-研究了处于基态（S 0）和第一激发单重态（S 1）的具有强肝保护作用的溴取代化合物的几何结构。分别采用311 ++ G **方法。发现该分子以两种形式存在，其焓差小于3.32 kcal / mol;它们的旋光度和反式均存在。后者是气相中的优选取向。 S_1状态是〜1（π，π*）状态，其从吡喃酮环中的双键的区域到连接2-吡喃酮和苯环的核间键的区域发生π电子转移。根据50-4000 cm〜（？1）范围内的实验红外光谱对3-溴-6-（4-氯苯基）-4-硫甲基-2H-吡喃-2-酮分子进行了完整的振动分析和DFT / 6- 311 ++ G **计算薄纱和反式异构形式的振动频率。基于沿着内部坐标的势能分布的光谱分配确认了分子的非平面结构。

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