Synthesis and structure dependent photophysical properties of novel 2-pyrazolines

Abstracts zoline derivatives (6–10) were synthesized from dibenzalacetones (1–5), formic acid and hydrazine hydrate in ethanol. The structures were elucidated by UV–Vis, FT-IR, ESI-MS, 1H NMR, 13C NMR, and microanalysis. Absorption and fluorescence spectra were recorded in methanol. Emissions occurred between 310 nm and 370 nm. Compound 6 with C-3 phenylvinyl (styryl) substituent showed remarkable red shift both in absorption and emission in comparison to compound 0 with C-3 phenyl substituent. Substitutions in compound 6 did not shift the band positions but intensity of emission increased with chloro and bromo substituents in o- and p-positions in styryl group. Compound, 10 with p-bromo substituent was found to have maximum emission intensity.