Zamora Miguel A, Suvire Fernando D, Enriz Ricardo D
Departamento de Química, Universidad Nacional de San Luis, Chacabuco 917, 5700 San Luis, Argentina.
J Comput Chem. 2008 Jan 30;29(2):280-90. doi: 10.1002/jcc.20789.
The multidimensional conformational potential energy hypersurfaces (PEHSs) for cis-cis-cis 1,4,7 cyclononatriene (I), Tribenzocyclononatriene (TBCN) (II), and cis-cis-cis cyclic triglycine (III) were comprehensively investigated at the Hartree-Fock (HF/6-31G(d)) and density functional theory (B3LYP/6-31G(d,p)) levels of theory. The equilibrium structures, their relative stability, and the transition state (TS) structures involved in the conformational interconversion pathways were analyzed. Altogether, four geometries (two low-energy conformations and two transition states) were found to be important for a description of the conformational features of compounds I-III. B3LYP/aug-cc-pvdz//B3lYP/6-31G(d,p) and MP2/6-31G(d,p)//B3LYP/6-31G(d,p) single point calculations predict that the conformational interconversion between crown and twist forms requires 14.01, 26.71, and 17.79 kcal/mol for compounds I, II, and III, respectively, which is in agreement with the available experimental data. A topological study of the conformational PEHSs of compounds I-III was performed. Our results allow us to form a concise idea about the internal intricacies of the PEHSs of compounds I-III, describing the conformations as well as the conformational interconversion process in these hypersurfaces.
在Hartree-Fock（HF/6-31G(d)）和密度泛函理论（B3LYP/6-31G(d,p)）理论水平上，对顺-顺-顺1,4,7-环壬三烯（I）、三苯并环壬三烯（TBCN）（II）和顺-顺-顺环三甘氨酸（III）的多维构象势能超曲面（PEHSs）进行了全面研究。分析了平衡结构、它们的相对稳定性以及构象互变途径中涉及的过渡态（TS）结构。总共发现四种几何结构（两种低能构象和两种过渡态）对于描述化合物I-III的构象特征很重要。B3LYP/aug-cc-pvdz//B3LYP/6-31G(d,p)和MP2/6-31G(d,p)//B3LYP/6-31G(d,p)单点计算预测，对于化合物I、II和III，冠型和扭曲型之间的构象互变分别需要14.01、26.71和17.79 kcal/mol，这与现有的实验数据一致。对化合物I-III的构象PEHSs进行了拓扑研究。我们的结果使我们能够对化合物I-III的PEHSs的内部复杂性形成一个简洁的概念，描述这些超曲面中的构象以及构象互变过程。
