Dibenzofuran Based Donor-Pi-Acceptor Molecules: Effect of Azo and Aminomethylene Linkages on Photophysical and NLO Properties.

We report here dibenzofuran-based D-π-A molecules containing azo and aminomethylene linkages. Both linkages are used to attach donor dibenzofuran to various active methylene compounds, such as un/substituted barbituric acid, Meldrum's acid, etc. Compounds 8a-c and 9a-f are studied for their photophysical properties, aggregation-induced emission in polar aprotic solvents and mercury sensing done with compound 9f. The DFT and TD-DFT calculations are performed to correlate the observed photophysical properties with calculated properties, which are further used to confirm the intramolecular charge transfer for both azo and aminomethylene linkages in excited states. Designed dibenzofuran-based D-π-A molecules are planar in both ground and excited states, making them suitable candidates for non-linear optical properties. The first hyperpolarizability values are calculated to explore the effect of the replacement of the azo linkage by the aminomethylene linkage on NLO properties.