Theoretical Studies for the Structural Properties and Electron Transfer Reactivity of C4H5N/C4H5N+ Coupling System

Abstract

The geometries and vibrational frequencies of pyrrole, pyrrole cation, and their corresponding encounter complexes have been determined using density functional theory (DFT) and/or ab initio methods with 6-31G* and/or 6-311+G* basis sets. Optimizations indicate that there are three stable complex modes. One mode has the ring−ring parallel contact (face−face) and each N atom in two rings is vertically over the center of another ring (complex 1). In the second mode (complex 2), two rings are also parallel, but they are directly contacted by only one N−C bond in each ring (side-side). The third mode (complex 3) is H−bond mode, in which the N−H of one pyrrole ring is nearly collinearly directed to the N center of another pyrrole ring and two rings are perpendicular to each other. For three-encounter complexes, their main bond lengths are between those of the pyrrole and those of the pyrrole cation. The character contact distances are 2.754 A (C3···C13), 2.727 A (C3···C12), and 2.632 A (N1···H16) at the B3P86/...