Experimental (FT-IR, FT-Raman, and NMR) and DFT studies of the structures and spectral properties of diphenylcarbazone and diphenylthiocarbazone

•Diphenylcarbazone and Dipheylthiocarbazone are commonly used analytical reagents for detecting various metals by forming colorful complexes.•The analysis of the rotational isomers of these molecules was systematically carried out to determine the more stable isomer and tautomeric form in the gas and aqueous phase.•Experimental FTIR-IR, FT-Raman, and NMR spectra of these molecules were recorded, and the results were supported by DFT calculations.•The effect of solvents on the conformational stability of the molecules was theoretically examined.