Laboratory of Spectroscopy, Molecular Modeling, Materials, Nanomaterials, Water, and Environment, Faculty of Sciences, Mohammed V University, Av Ibn Battouta, Rabat B.P. 1014, Morocco.
Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, 94010 Créteil, France.
Molecules. 2023 Apr 13;28(8):3419. doi: 10.3390/molecules28083419.
The microwave spectra of benzothiazole were measured in the frequency range 2-26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer. Hyperfine splittings arising from the quadrupole coupling of the N nucleus were fully resolved and analyzed simultaneously with the rotational frequencies. In total, 194 and 92 hyperfine components of the main species and the S isotopologue, respectively, were measured and fitted to measurement accuracy using a semi-rigid rotor model supplemented by a Hamiltonian accounting for the N nuclear quadrupole coupling effect. Highly accurate rotational constants, centrifugal distortion constants, and N nuclear quadrupole coupling constants were deduced. A large number of method and basis set combinations were used to optimize the molecular geometry of benzothiazole, and the calculated rotational constants were compared with the experimentally determined constants in the course of a benchmarking effort. The similar value of the quadrupole coupling constant when compared to other thiazole derivatives indicates only very small changes of the electronic environment at the nitrogen nucleus in these compounds. The small negative inertial defect of -0.056 uÅ hints that low-frequency out-of-plane vibrations are present in benzothiazole, similar to the observation for some other planar aromatic molecules.
使用脉冲分子喷射傅里叶变换微波光谱仪，在 2-26.5GHz 的频率范围内测量了苯并噻唑的微波光谱。完全解析了来自 N 核的四极耦合的超精细分裂，并与旋转频率同时进行了分析。总共测量并拟合了主要物质和 S 同位数的 194 个和 92 个超精细分量，其精度达到了测量精度，使用了补充有考虑 N 核四极耦合效应的哈密顿量的半刚性转子模型。推导出了高精度的转动常数、离心变形常数和 N 核四极耦合常数。使用了大量的方法和基组组合来优化苯并噻唑的分子几何形状，并在基准测试过程中比较了计算的转动常数与实验确定的常数。与其他噻唑衍生物相比，四极耦合常数的值相似，表明这些化合物中 N 核的电子环境仅发生了很小的变化。负的惯性缺陷值为-0.056 uÅ，表明苯并噻唑中存在低频面外振动，类似于一些其他平面芳香族分子的观察结果。
