Oxygen bridged nitroanilines for quadratic nonlinear optics

Several nitro aromatic compounds bridged by an oxygen atom have been synthesized and their linear and nonlinear optical properties have been investigated. In one of the compounds (1), a powder SHG efficiency of 6.2 times of urea was observed while its absorption lies in the UV region. The highest molecular hyperpolarizability β, measured was 230×10⁻³⁰ for a compound (8f) with increased conjugation. Thermal stability of these compounds has been checked using differential scanning calorimetry and the decomposition temperature (T_d) was found to be high and lying between 266-298 °C. These molecules have potential importance as thermally stable, visible-transparent second order NLO materials.