Computational and spectroscopic studies of biologically active coumarin-based fluorophores.

We used density functional theory (DFT) calculations to examine the various molecular properties of two coumarin derivatives, namely 4-(5-amino-[1,3,4]thiadiazol-2-ylsulfanylmethyl)-7-methyl-chromen-2-one and 4-(5-amino-[1,3,4]thiadiazol-2-ylsulfanylmethyl)-7-methoxy-chromen-2-one at different levels of theory and basis sets. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies revealed that the investigated molecules were chemically active with a tendency for molecular interactions. The theoretical vibrational frequencies of these molecules were found to be consistent with the experimentally obtained frequencies.