Studies on the synthesis and fluorescent properties of long-chained 2-(5-alkyl-1, 3, 4-oxadiazol-2-yl)-3H-benzo[f]chromen-3-ones

Abstract

The synthesis and fluorescent properties of some new benzocoumaryl heterocyclic molecules are presented. Condensation of 2-hydroxy-1-naphthaldehyde with diethyl malonate in the presence of catalytic amount of piperidine in ethanol affords benzocoumarin-3-ethyl carboxylate 2 in fairly good yield (90%). Further the compound 2 on treatment with hydrazine hydrate afforded compound 3 with excellent yield (95%). Thus compounds 4a-e have been obtained by direct cyclization of 3 with various fatty acids in the presence of POCl 3 . The structures of all newly synthesized compounds were confirmed by IR, 1 H NMR, 13 C NMR and UPLC-Mass spectral data. Fluorescent experimental results revealed remarkable photoluminescence properties. Luminescent properties of all newly synthesized compounds were determined and observed that they exhibited strong blue-green fluorescent properties. The fluorescence spectral properties of compounds 4a-e are similar to each other and the Stoke's shift ranges from 54 to 59 nm. Both the absorption and fluorescence maxima of the benzocoumarin-oxadiazole compounds showed good bathochromic shift.