杯[4]吡咯与含氧阴离子及其离子对弱相互作用的理论研究

在M06-2X/6-31+G(d,p)计算水平上,对杯4]吡咯(CP)与3种不同构型的含氧阴离子OH-(C(v)、NO3-(D3h)、ClO4-(Td)形成的组装体系进行了理论研究。比较了各体系的构型、结合能、自然键轨道(NBO),利用多功能波函数软件Multiwfn对相互作用力等进行可视化分析。结果发现,无论主-客体的组装计量比是1∶1还是2∶1,阴离子的构型直接影响组装体系的构型。阴离子空间构型越大、整体电负性越强,越倾向于2∶1复合体系。考虑到杯4]吡咯是典型的离子对受体,本文还研究了主体与NH4+-阴离子的离子对体系的相互作用。在离子对的组装过程中,由于阴、阳离子间的作用占据了主导,从而减弱了阴离子与主体间氢键作用,无论阴离子构型如何,主体与离子对的组装都倾向于1∶1的作用体系。本文结果对深入理解杯吡咯类受体的离子识别作用本质,拓展该类超分子主体的应用范围具有重要的理论意义。

Theoretical Investigation on the weak Interaction between Calix[4]pyrrole and Oxoanions/ Ion pairs

The systematic theoretical study on the assembled systems formed by calix4]pyrrole (CP) and anions with different configurations, such as OH- (C?v), NO3- (D3h),and ClO4-(Td)), were explored at the M06-2X/6-31 G (d, p) level of theory. Based on the optimized geometries, the natural bond orbital (NBO) analyses, binding energies, and the multifunctional wavefunction (Multiwfn) analyses for these systems were carried out comparatively. The calculated results showed that the anion configuration had a direct effect on the structure of assembled systems no matter the host-guest stoichiometry as 1:1 or 2:1. The larger the steric size and the stronger the electronegativity of an anion was, the more easily the 2:1 complex formed. Considering calix4]pyrrole as an ion-pair receptor, the interaction between CP and NH4 -X (X= OH-, NO3-, and ClO4-) ion-pairs were also investigated in this work. In the assembled systems formed by CP and ion-pairs, the hydrogen-bond interaction between anion and CP weakened due to the ion-pairing of anion and cation as the dominant force. The 1:1 stoichiometric systems of CP and ion-pairs were more advantageous whatever anionic spatial configurations. This work has great theoretical significance in understanding deeply of the calixpyrroles recognition and in extending the range of application of them as the supramolecular hosts.