水杨酸甲酯及其与硝酸铁硝化产物光谱性质的比较(英文)

Comparison among the Spectral Properties of Methyl Salicylate and Its Nitration Products by Iron (Ⅲ) Nitrate

通过硝酸铁和水杨酸甲酯的硝基化反应,合成了3-硝基水杨酸甲酯和5-硝基水杨酸甲酯.并用红外光谱、核磁共振光谱、紫外-可见吸收光谱和荧光光谱对产物进行了表征.用量子化学计算结果对其红外光谱、核磁共振光谱、紫外-可见吸收光谱和荧光光谱的性质差异进行了解释.B3LYP/6-31G**和自然价键轨道方法计算结果表明,由于3-硝基水杨酸甲酯具有更强的分子内氢键,其羟基和羰基的红外吸收比5-硝基水杨酸甲酯的红移了,酚羟基的氢谱移向了高位移,紫外吸收产生了增色效应.基于CIS/6-31G**方法,计算了水杨酸甲酯和3-硝基水杨酸甲酯基态和激发态下的分子内质子转移的势能曲线,由势能曲线进一步得到它们的Stokes位移分别为8.4×103和8.9×103cm-1.所有结果表明,由于分子内氢键强弱不同,导致水杨酸甲酯、3-硝基水杨酸甲酯和5-硝基水杨酸甲酯的光谱性质不一样.

Methyl 3-nitrosalicylate （3-MNS） and methyl 5-nitrosalicylate （5-MNS） were synthesized by a nitration reaction between methyl salicylate （MS） and iron （Ⅲ） nitrate under reflux. 3-MNS and 5-MNS were characterized by infrared spectra （IR）, proton nuclear magnetic resonance spectra QH-NMR）, electronic absorption spectra （UV-Vis）, and photoluminescence （PL）. The structures of 3-MNS and 5-MNS were fully optimized at the B3LYP/6-31G^＊＊ level. The optimized results and nature bond orbital （NBO） analysis results were used to illustrate the red-shift of the O-H and C=O stretching vibrations in the IR, the lower field shift of the phenol hydroxyl proton chemical shift in ^1H-NMR, and the bathochromic shift in the UV-Vis spectra of 3-MNS. Potential energy surfaces for the intramolecular proton transfer of ground （GSIPT） and excited （ESIPT） states of MS and 3-MNS were obtained and the Stokes-shift values for MS and 3-MNS were computed to be 8.4 ×10^3 and 8.9×10^3 cm^-1 using CIS/6-31G^＊＊, respectively. All these results demonstrate that differences in intramolecular hydrogen bonding in MS, 3-MNS, and 5-MNS give rise to large differences in their spectral properties.