Fourier-Transform Infrared (FT-IR) spectroscopy supported by Raman spectroscopy has been employed to
explain the conventional and unconventional hydrogen bonding present in the 4,40thiodiphenol: hexamine
and 4,40sulfonyldiphenol: hexamine cocrystals. The possible internal and external vibrational
modes are predicted through factor group analysis. Influence of intra molecular charge transfer (ICT)
interaction caused by the strong ionic ground state hydrogen bonding between charged species, giving
rise to a non centro symmetric structure which is a criterion for second harmonic generation (SHG) efficiency
has been discussed. Intense low wave number hydrogen bond vibrations in Raman which arise
due to electron–phonon coupling are analyzed. Optical quality of adducts is identified through UV–Vis
analysis. The second harmonic generation efficiency of both adducts is determined by Kurtz–Perry
method