Synthesis and photophysical study of new fluorescent proton transfer dihydropyrimidinone hybrids as potential candidates for molecular probes

A series of fluorescent aldehydes were synthesized and used in a conventional Biginelli multicomponent reaction under Lewis acid CeCl3·7H2O catalysis. The photoactive hybrid dihydropyrimidin-2-ones (Flu-DHPM) were isolated in reasonable to good yields. The compounds presented emission in the visible region with a large Stokes’ shift and low quantum yield of fluorescence as expected, ascribed to the phototautomerism in the excited state (ESIPT). Moreover, the ESIPT process allowed for Flu-DHPM with intense emission in the solid state compared to the dihydropyrimidin-2-ones (DHPMs) without the benzazolic core. The observed photophysical features were successfully used to explore these compounds as fluorescent probes in biological media. In addition, cell imaging experiments demonstrated that these photoactive hybrids have potential for use as cellular markers.