Pii: S0022-328x(00)00589-1

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 (b) ranging from 8.6 to 1226.0×10 cm esu 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. © 2000 Elsevier Science B.V. All rights reserved.