Synthesis and study of fluorescence properties of novel pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidin-5(6H)-one derivatives

Abstract

New pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidin-5(6H)-one derivatives 5 were prepared by cyclocondensation reaction between heterocyclic o-aminonitriles 3 and carboxylic acids 4 in the presence of sulfuric acid as catalyst. This procedure provides the desired compound in good yield with a simple one-step methodology. The obtained products show interesting fluorescence properties in both solution and solid state; in this way several spectra of absorption and emission were measured for selected compounds 5b, 5e, 5g and 5j, showing a broad and intense emission band around of 470nm. In other to understand the electronic transition processes, theoretical calculations were performed at TD-DFT level, using B3LYP as functional and 6-31(d,p) as basis set, finding a good agreement with experimental measurements.