Tautomeric purine forms of 2-amino-6-chloropurine (N9H10 and N7H10): Structures, vibrational assignments, NBO analysis, hyperpolarizability, HOMO-LUMO study using B3 based density functional calculations

► FT-IR and FT-Raman investigations of ACP (N9H10) were carried out. ► Geometrical parameters and vibrational frequencies of purine tautomers ACP (N9H10 and N7H10) were calculated. ► The complete assignments are performed on the basis of the potential energy distribution (PED). ► Hyperpolarizability, HOMO and LUMO energies were calculated.