Nonlinear optical properties of ionic NLO chromophores: An attempt to bridge the gap between computation and experiment

We present a quantum chemical analysis of the molecular structure and first hyperpolarizabilities of a series of stilbazolium ions and compare their results with corresponding neutral molecules. The molecular geometries are obtained via B3LYP/6-31G** optimization, including the self-consistent reaction field/polarizable continuum model (SCRF/PCM) approach. The static first hyperpolarizabilities (00) are calculated using the ab initio coupled perturbed Hartree-Fock (CPHF) method, while the dynamic first hyperpolarizability (beta) is investigated using the ZINDO/correction vector (CV) method, including solvent effects. The effects of donor-acceptor properties, solvent polarity, the dispersion effect, and aggregation on the first hyperpolarizibility are methodically evaluated with an attempt toward developing the engineering guidelines for the enhancement of the molecular optical nonlinearities of charged chromophores. We compare our theoretical results with the experimental values wherever available in the literature and evaluate the results in detail about the agreements and disagreements between theoretical and experimental findings. (c) 2005 Wiley Periodicals, Inc. Int J Quantum Chem 105: 348-358, 2005.