Mesoionic rings as efficient asymmetric bridges for the design of compounds with large optical nonlinearities

Through semi-empirical AM1 calculations of second-order nonlinear optical properties of molecules containing mesoionic rings, we propose that these should be considered as promising substitutes for the polyene bridges normally present in compounds displaying large hyperpolarizabilities, β. In order to substantiate our reasoning, we computed the AM1 static hyperpolarizabilities, β(0), of twenty molecules whose experimental values have already been determined. Our results indicate that the AM1 β(0) are indeed able to yield qualitative inferences about experimentally obtained values. Finally, we present a number of theoretically designed molecular structures which should display high hyperpolarizability values.