Donor-linker-acceptor (D-π-A) diazine chromophores with extended p-conjugated cores: synthesis, photophysical and second order nonlinear optical properties

The synthesis of a series of push-pull pyrimidine and quinoxaline chromophores with extended p-conjugated cores is reported. Starting from a bromoarylvinyldiazine derivative, the key step in the preparation of the chromophores consists of a Sonogashira cross-coupling reaction. The photophysical properties of the compounds are described. A strong positive emission solvatochromism, typical for dyes presenting Intramolecular Charge Transfer (ICT), is observed, in particular for amino substituted derivatives with larger solvatochromic range than known analogous chromophores with smaller p-conjugated cores. The second order non linear optical (NLO) properties were investigated for some of the compounds and a comparison with the NLO responses of already described diazine chromophores exhibits a significant enhancement of the NLO properties by extension of the pi-conjugated core.