2,2'-联噻吩的构象分析：使用(13)C卫星光谱的(1)H液晶核磁共振研究。

Conformational analysis of 2,2'-bithiophene: a (1)H liquid crystal NMR study using the (13)C satellite spectra.

作者信息

Concistré Maria, De Lorenzo Luana, De Luca Giuseppina, Longeri Marcello, Pileio Giuseppe, Raos Guido

机构信息

Dipartimento di Chimica, Universita della Calabria, Via P. Bucci, 87030 Arcavacata di Rende (Cs), Italy.

出版信息

J Phys Chem A. 2005 Nov 10;109(44):9953-63. doi: 10.1021/jp054003f.

DOI:10.1021/jp054003f

PMID:16838912

Abstract

We have obtained a very large data set of spectral parameters from the analysis of (1)H NMR and (13)C satellite spectra of 2,2'-bithiophene dissolved in anisotropic, partially orienting mesophases. In particular, this parameter set includes 33 dipolar couplings, which are directly related to the interatomic distances, the dihedral angle phi between the two thiophenic rings, and the anisotropic solute-solvent interaction potential. This allows an exhaustive investigation of the conformational equilibrium of 2,2'-bithiophene in a liquidlike phase. Comparison with the predictions of high-level theoretical calculations for the isolated molecule provides evidence of a strong flattening as well as the sharpening effect of the medium on the conformer population. The approximations needed to apply vibrational corrections to flexible molecules are discussed in detail and some general conclusions concerning their effect on structure and conformational equilibria are proposed.

摘要

我们通过对溶解在各向异性、部分取向中间相中的2,2'-联噻吩的(1)H NMR和(13)C卫星光谱进行分析，获得了一个非常大的光谱参数数据集。特别地，该参数集包括33个偶极耦合，它们与原子间距离、两个噻吩环之间的二面角φ以及各向异性溶质-溶剂相互作用势直接相关。这使得我们能够对2,2'-联噻吩在类液相中的构象平衡进行详尽的研究。与孤立分子的高水平理论计算预测结果进行比较，提供了介质对构象异构体群体的强烈扁平化以及锐化效应的证据。详细讨论了对柔性分子应用振动校正所需的近似方法，并提出了一些关于它们对结构和构象平衡影响的一般结论。