This paper reports results of a theoretical study about the effect of ionization on the infrared and Raman spectra of α,α'-bis(aminomethyl)quaterthiophene with the objective of obtaining a deeper insight into the geometry and spectral changes occurring upon doping of the oligothiophenes and polythiophene. For these purposes, we determine the structures, vibrational frequencies and infrared intensities of the neutral compound and of its radical cation and dication. Ab initio calculations, at the B3LYP/6-31G * * and RHF/6-31G * * levels of theory, are employed to assess the structural and spectral information for the neutral and charged states.