Hydrolysis and substitution effects on the optical properties of coumarin derivatives studied by vibrational spectroscopy and DFT calculation

A series of coumarin derivatives have been successfully synthesized. All compounds have been characterized by means of IR and Raman vibrational spectroscopic techniques at the solid state level. Optical absorption and photoluminescence measurements were performed on thin solid films. All compounds show absorption bands involving both pi-pi* and n-pi* electronic transitions and strong emissions in the blue-green spectral range. A large Stokes shift has been noticed and may explain the light emission stability even at ambient temperature. We have mainly interested to the hydrolysis and the methoxy substitution at position 8 effects the optical properties using experimental results and theoretical calculations. Discussions revealed that the maximum of absorption and emission spectra were affected and shifted by tuning the gap energy and enhancement of the Stokes shift. One noticed a good agreement between experimental and theoretical results. (C) 2018 Published by Elsevier B.V.