Polyhedral-based nonlinear optical materials. Part 1. Theoretical investigation of some new high nonlinear optical response compounds involving carboranes and charged aromatic donors and acceptors

A calculational investigation using semiempirical methods of the molecular and electronic structures, along with the nonlinear optical responses, of a series of compounds in which icosahedral carborane polyhedra bridge charged aromatic donor and acceptor moieties, specifically tropyl (C₇H₇⁺) and cyclopentadienyl (C₅H₅^-) groups, found that these molecules show exceptionally large calculated second-order responses. These compounds were found to give calculated first hyperpolarizabilities (β) ranging from 8.6 to 1226.0×10^-30 cm⁵ esu^-1 at 0.5 eV excitation energy. These nonlinear optical responses are understood within the framework of the two-state model using molecular orbital and electronic structure considerations.