Abstract

Relativistic two-component density functional theory employing sf-X2C-S-TD-DFT/SOC method has been used to explore the detailed electronic spectra of molecules with thiazole skeleton named as ethyl 2-(2-Iodobenzylidenehydrazinyl)thiazole-4-carboxylate (2d) and its meta and para isomers (2e and 2f). Four different kinds of functionals including hybrid, meta-hybrid and long-range types have been employed to explore coupled states in 2d, 2e and 2f. Electronic excited states computed with different functionals has been benchmarked with second-order algebraic diagrammatic construction method i.e. ADC(2). However, spin–orbit couplings between electronic states of different multiplicities are only computed with sf-X2C-S-TD-DFT/SOC method. It has been explored that; excited electronic states which involved transitions into sigma antibonding orbital (σ∗) between carbon and iodine atom gave birth to strong spin–orbit couplings. Thus, transitions that involve addition or removal of electron density across iodine atom lead to strongly coupled states.