Synthesis, characterization, DFT and TD-DFT study of novel bis(5,6-diphenyl-1,2,4-triazines)

•Synthesis of novel series of bis(5,6-diphenyl-1,2,4-triazines).•Confirmation of their chemical structures by spectroscopic techniques.•Studies of their absorption and excited-emission spectra experimentally in ethanol solvent.•Calculation of their electronic absorption and emission spectra in gas and ethanol solvent using time dependent density functional theory (TDDFT). Due to the numerous biological as well as pharmacological activities of 1,2,4-triazine derivatives, we reported a synthesis of novel series of bis(5,6-diphenyl-1,2,4-triazines) via alkylation of 5,6-diphenyl-1,2,4-triazine-3(4H)-thione with the appropriate bis(halo) compounds in ethanolic KOH. The chemical structures of these compounds were confirmed by spectroscopic techniques. The absorption and excited-emission spectra of the studied novel series were monitored experimentally in ethanol solvent. The molecular structures of these triazines were optimized using B3LYP/6–31G(d) level of theory. The electronic absorption and emission spectra of the novel compounds, in gas and ethanol solvent, were calculated using time dependent density functional theory (TDDFT) at mPW1PW91/ 6–31 G (d) level. The obtained theoretical results were compared to experimental ones. The results show that, the computational optical properties of the studied novel series are in agreement with experimental results. [Display omitted]