摘要
在B3LYP/6-311++G^(**)水平上利用振动二阶微扰理论对2-吡啶酮,尿嘧啶及其5-取代物:5-溴-尿嘧啶、5-氯-尿嘧啶、5-氟-尿嘧啶、5-三氟甲基-尿嘧啶、5-腈-尿嘧啶、5-羟基-尿嘧啶(排斥式和氢键式)、胸腺嘧啶分子做了非谐性计算,研究这些分子在1 600~1 850 cm-1指纹区间振动模式的非谐性频率,非谐性常数与取代基影响的关系,并计算了费米共振峰,用振动激子模型模拟了耦合常数.和2-吡啶酮中的C=O和C=C伸缩振动相比,不同的5位取代基引起嘧啶分子中C=O跃迁偶极矩波动,取代基的电负性使C=C伸缩的跃迁偶极矩增加,并使得嘧啶分子中C=O和C=C伸缩振动之间的相互作用值改变显著,跃迁偶极耦合常数值和跃迁振动电子立方密度充分说明电子相互作用对模式间的耦合起着关键作用.
Anharmonic calculations were performed on 2-pyridone, uracil, and its 5-substituted mole-cules, such as 5-brom-uracil, 5-chlor-uracil, 5-fluor-uracil, 5-trifluormethyl-uracil, 5-cyano-uracil,5-hydroxyl （repulsive）-uracil, 5-hydroxyl （hydrogen bonded）-uracil, and 5-methyl-uracil （thymine）using the second order vibrational perturbation theory at B3LYP / 6-311＋＋G^＊＊ level. Anharmonic frequencies, diagonal and off-diagonal anharmonicities in the finger-print range of 1 600 - 1 850 cm^-1were studied. Fermi resonance bands were also presented. The coupling constants were evaluated usingvibrational excitonic model. In all case, transition dipole coupling constants and vibrational transitiondensity cube analysis sufficiently illustrated that electron interaction is key in the coupling betweenmodes, and vice versa, changed their vibrational frequencies and intensities. Compared to the C = Oand C = C stretching in 2-pyridine, various substituents on 5-position in the pyrimidine ring inducefluctuations of the transition dipole moment of C =O, and enhance that of C =C stretching due to negative electricity. The interactions between C =O and C =C are significantly altered. The transition dipolecoupling approximation and vibrtional transition density cube analysis demonstrate that electro interactions play the key role in the intermode coupling.
出处
《化学研究》
CAS
2018年第1期49-58,共10页
Chemical Research
基金
菏泽学院校级基金(XY13BS03)
关键词
尿嘧啶
尿嘧啶的5位取代物分子
红外光谱
非谐性振动耦合
uracil
5-substituent uracil derivatives
infrared spectroscopy
anharmonic vibrationalcoupling
