Optical second order nonlinearities in new chromophores obtained by selective mono-reduction of dinitro precursors.

Three new push-pull chromophores of potential interest in second order nonlinear optical applications were synthesized and characterized, also by EFISH determination of molecular second order NLO properties. The chromophores contain a phenyl-azo unit coupled with fluorenonic, stilbenic or 1,3,4-thia-diazolic groups and are OH-functionalized to prompt easy covalent insertion in polymer chains. The selective reduction of only one of the two chemically equivalent nitro groups in the starting precursors is the key step of the synthetic pathway affording the chromophores. These show good chemical and thermal stability. The X-ray structural determination of the fluorenone derived chromophore is also reported.