Experimental and ab-initio studies of the spectroscopic properties of N,N′,N″-triphenylguanidine and N,N′,N″-triphenylguanidinium chloride

Triphenylguanidinium chloride was synthesized and the corresponding infrared (IR) spectra was measured. Four different conformers of triphenylguanidine, two neutral and two protonated forms, have been studied by means of ab-initio calculations. The four geometries were optimized using Hartree–Fock and DFT/B3LYP 6-31G(d,p)+ level of theory. The calculated vacuum equilibrium geometries are compared with several existing crystal structures. The IR spectra of the neutral and protonated molecules were also computed and the vibrational modes were assigned to the most intense calculated frequencies. The optimized geometries were used in a Time Dependent Density Functional Theory calculation of the optical absorption spectra. Both the IR and visible ab-initio spectra were compared with the triphenylguanidine and triphenylguanidinium chloride experimental spectra.