Puzzarini Cristina
Dipartimento di Chimica "Giacomo Ciamician", Università di Bologna , Via Selmi 2, I-40126 Bologna, Italy.
J Phys Chem A. 2015 Nov 25;119(47):11614-22. doi: 10.1021/acs.jpca.5b09489. Epub 2015 Nov 16.
The structures, relative stabilities, and rotational and vibrational parameters of the Z-C-, E-C-, and N-cyanomethanimine isomers have been evaluated using state-of-the-art quantum-chemical approaches. Equilibrium geometries have been calculated by means of a composite scheme based on coupled-cluster calculations that accounts for the extrapolation to the complete basis set limit and core-correlation effects. The latter approach is proved to provide molecular structures with an accuracy of 0.001-0.002 Å and 0.05-0.1° for bond lengths and angles, respectively. Systematically extrapolated ab initio energies, accounting for electron correlation through coupled-cluster theory, including up to single, double, triple, and quadruple excitations, and corrected for core-electron correlation and anharmonic zero-point vibrational energy, have been used to accurately determine relative energies and the Z-E isomerization barrier with an accuracy of about 1 kJ/mol. Vibrational and rotational spectroscopic parameters have been investigated by means of hybrid schemes that allow us to obtain rotational constants accurate to about a few megahertz and vibrational frequencies with a mean absolute error of ∼1%. Where available, for all properties considered, a very good agreement with experimental data has been observed.
已使用最先进的量子化学方法评估了Z-C-、E-C-和N-氰基亚甲基亚胺异构体的结构、相对稳定性以及旋转和振动参数。通过基于耦合簇计算的复合方案计算了平衡几何结构，该方案考虑了外推到完整基组极限和核心相关效应。事实证明，后一种方法提供的分子结构在键长和键角方面的精度分别为0.001 - 0.002 Å和0.05 - 0.1°。通过耦合簇理论系统地外推了考虑电子相关性的从头算能量，包括单重、双重、三重和四重激发，并对核心电子相关性和非谐零点振动能量进行了校正，已用于以约1 kJ/mol的精度准确确定相对能量和Z-E异构化势垒。通过混合方案研究了振动和旋转光谱参数，这使我们能够获得精度约为几兆赫兹的旋转常数和平均绝对误差约为1%的振动频率。在所有可用的情况下，对于所考虑的所有性质，均观察到与实验数据非常吻合。
