Insights into structural, solvent effect, molecular properties and NLO behavior of hemithioindigo-photoisomerization : A DFT study

Abstract The influence of the strength of the electron donor groups on the quantum chemical properties of the Z and E isomerization of some hemithiondigo molecules was investigated via density functional theory (DFT). Electronic, spectroscopic, and thermodynamic properties were studied using DFT and TD-DFT. It was found that 3a is the most reactive molecule compared to 3b and 3c. Moreover, the Z isomer of 3a exhibited small excitation energy, large absorption bands, charge transfer, chemical reactivity, and a higher reaction rate. Molecule 3a also displayed a high electrostatic potential. The most significant NLO response was obtained for Z isomers of 3a (191.80 × 10−30 esu), mainly due to the strong electron-donor group (Diphenylaminyl (-N(Ph)2) present at the para-position of the stilbene part. Based on all the obtained results, it can be concluded that the Z isomer of 3a is a promising HTI switch.