Synthesis and photophysical studies on 5-ethoxycarbonyl-4-cinnamyl-6-methyl- 3,4-dihydropyrimidine-2(1H)-one in various solvents

The 5-ethoxycarbonyl-4-cinnamyl-6-methyl-3,4-dihydropyrimidine-2(1H)-one (DHPM) was synthesized via Biginelli reaction and was characterized by NMR, IR, UV−Visible absorption and fluorescence spectroscopy. The fluorescence of the compound exhibits red shift from its absorption spectra and correlated with the solvent polarity. The quantum yield of fluorescence of the DHPM was found to vary with solvent polarity. The absorption spectrum of DHPM overlaps significantly with anthracene fluorescence spectrum. Therefore fluorescence quenching experiments were performed in 1,4-dioxane. The fluorescence of anthracene was found to be quenched and quenching is in accordance with Stern-Volmer relation. The Stern-Volmer constant (KSV = 2.52 x 103 M-1) was obtained. The quenching rate constant (kq = 7.145 x 1011 M-1 s-1) was calculated from the fluorescence lifetime of anthracene measured on time resolved fluorimeter (TRF) in absence of DHPM. The fluorescence quenching explained on the basis of energy transfer from anthracene to DHPM derivative. The rate constant as well as efficiency of energy transfer depends on the distance between donor and acceptor and found to be r = 6.39 nm which indicates energy transfer.