Theoretical Nonlinear optics equivalence between mesoionic and polyenic bridges in push-pull compounds

In this work we report a semiempirical investigation with the purpose of establishing an equivalence in terms of the value of the first static hyperpolarizability, beta(0), of push-pull compounds of the type electron-acceptor( A)-bridge-electron-donor(D), either formed by polyenic bridges or by mesoionic bridges, keeping unchanged both D and A groups. The ground state geometries of the molecules were optimized via AM1 using Mopac93r2 program. The value of beta(0) was calculated by time-dependent Hartree-Fock (TDHF). Our results indicate that a bridge formed by a single mesoionic ring can be equivalent to seven or more conjugated double bonds, depending on the ring, reaffirming that mesoionic rings constitute promising materials for photonics applications.