Theoretical investigation of structure diversity and electronic properties in the series isomeric [26]hexaphyrin (1.1.1.1.1.1) and [28]hexaphyrin (1.1.1.1.1.1)

By analyzing the geometric structure, FMOs, electronic transition properties and nonlinear optical properties of five isomeric [26]hexaphyrin (1.1.1.1.1.1) and corresponding [28]hexaphyrin (1.1.1.1.1.1) molecules, thienyls act as the electron donating groups and influence more tremendous to the FMOs and electronic transition properties. Absorption characteristics of B-like band of aromatic molecules originate from the transition between HOMO (HOMO−1) and LUMO (LUMO+1), but for the Hückel antiaromatic molecules, the strongest absorption characteristics come from the HOMO → LUMO+2 and HOMO−2 → LUMO. For the molecules of the same shape, the β0 value of antiaromatic molecules is greater than that of aromatic molecules, because of their different transition properties.