Molecular properties of 5-(1H-Benzo[D]Oxa, thia, imid azole-2-Yl)-2-methyl quinazolin-4-ol fluorescent brighteners: Theoretical and experimental approach

Abstract

A series of seven new fluorescent brighteners 5-(1H-benzo[d]oxazole, thiazole, imidazole-2-yl)-2-methyl quinazolin-4-ol were synthesized by chemical reaction of 2-Methyl-4-oxo-3,4-dihydroquinazoline-5-carboxylic acid and derivatives of 2-aminophenol/2-aminothiophenol/1,2-phenylenediamine attributes to its computational and experimental comparison. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations was performed by PCM model maintaining C1 symmetry in ground state both in gas and DMF solvent. The electronic distribution over the molecules has built up strong relationship with its fluorescence quantum efficiency. HOMO and LUMO energies defined electron donor acceptor relationship and shows two distinct plane which are less responsive towards the π-π electronic transition and has inductive electronic effect control their fluorescence properties. The fluorescent brighteners 6a-6g exhibits 0.6–22% and 0.6–7.4% deviation for UV-absorption and fluorescence emission respectively. The theoretical and experimental results for absorption and emission are in well agreement that certainly believe to perform theoretical calculations before experimental setup. The thermally stable fluorescent brightening agents have been systematically investigated. The color space method was used to evaluate the brightening values on polyester fabrics in terms of L*, a* and b*.