Exploration of the aminomethylene linkage in carbazole-based donor–pi–acceptor molecules for AIE and hydrazine sensing

Abstract

Carbazole-based donor–pi–acceptor molecules with various active methylene compounds attached via aminomethylene and azo linkages are designed. All the compounds are synthesized and characterized and their photophysical properties are studied. The newly introduced aminomethylene linkage attached to various acceptor moieties in the carbazole-based donor–pi–acceptor molecules has a significant effect on the absorbance and emission band of all the studied compounds. All the compounds with aminomethylene linkages exhibit very good fluorescence in solid, aggregation and solution states. The azo-linked barbituric acid derivatives show significant red shifts in the emission band. Carbazole linked to barbituric acid through both aminomethylene and azo linkages is studied for hydrazine detection and shows significant differences. The NLO properties for all the compounds from both series are calculated using DFT methods, and the azo linkage is found to show prominent enhancement in the first-order hyperpolarizability (β) values.