Structural conformations, tautomerization and vibrational spectral study of 6-amino-1-methylpurine with density functional theoretical calculations

•The calculated vibrational values are in good agreement when they are compared with IR and Raman experimental data.•Amine–imine tautomerism is studied in detail.•The NBO analysis has been performed to elucidate the intra molecular interaction and delocalization.

The FT-IR and FT-Raman spectra of 6-amino-1-methylpurine (AMP) have been recorded in the region 4000–400 cm−1 and 3500–50 cm−1 respectively. The optimized geometry, frequency and intensity of the vibrational bands of AMP have been obtained by DFT level of theory using B3LYP method with 6-311++G(d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. Purines, including substituted purines and their tautomers, are the most widely occurring nitrogen-containing heterocyclic in nature. Purines and pyrimidines make up the two groups of nitrogenous bases, including the two groups of nucleotide bases. Two of the four deoxyribonucleotides and two of the four ribonucleotides, the respective building-blocks of DNA and RNA, are purines. The calculated vibrational values are in good agreement when they are compared with IR and Raman experimental data. Amine–imine tautomerism of 6-amino-1-methyl purine is studied in detail. In agreement with experimental results, it was found that imine tautomer is more stable than amine tautomer.

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