Density functional theory study of interaction, bonding and affinity of group IIb transition metal cations with nucleic acid bases

► We studied the complexes formed by free nucleobases and transition metal cations. ► We located the stable tautomers of the free nucleobases. ► The tautomerization paths of the nucleobases have been determined. ► We estimated the metal ion affinities for all the tautomers of the nucleobases. ► We calculated the enthalpy, entropy and free energy of the complexes at 298 K.