Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, NO-0315 Oslo, Norway.
J Phys Chem A. 2011 Jul 7;115(26):7559-65. doi: 10.1021/jp202319q. Epub 2011 Jun 7.
The microwave spectrum of 1-vinylimidazole has been investigated in the 21-80 GHz spectral region. The spectra of two conformers have been assigned. One of these forms is planar, while the other is nonplanar with the imidazole ring and the vinyl group forming an angle of 15(4)° from coplanarity. The planar form is found to be 5.7(7) kJ/mol more stable than the nonplanar rotamer by relative intensity measurements. The spectra of 10 vibrationally excited states of the planar form and one excited-state spectrum of the nonplanar form were assigned. The vibrational frequencies of several of these states were determined by relative intensity measurements. The microwave work has been augmented by quantum chemical calculations at the CCSD/cc-pVTZ, MP2/cc-pVTZ, and B3LYP/cc-pVTZ levels of theory. The B3LYP calculations predict erroneously that both forms of 1-vinylimidazole are planar, whereas the MP2 and CCSD calculations correctly predict the existence of a planar and a nonplanar conformer of this compound.
1-乙烯基咪唑的微波光谱已在 21-80GHz 光谱区域进行了研究。已分配了两种构象体的光谱。其中一种形式是平面的，而另一种是非平面的，咪唑环和乙烯基基团与平面形成 15(4)°的角度。通过相对强度测量发现，平面形式比非平面旋转体稳定 5.7(7)kJ/mol。已分配了平面形式的 10 个振动激发态和非平面形式的一个激发态光谱的光谱。通过相对强度测量确定了这些状态中的几个的振动频率。微波工作已通过在 CCSD/cc-pVTZ、MP2/cc-pVTZ 和 B3LYP/cc-pVTZ 理论水平的量子化学计算得到补充。B3LYP 计算错误地预测了 1-乙烯基咪唑的两种形式都是平面的，而 MP2 和 CCSD 计算正确地预测了该化合物存在平面和非平面构象体。
