A Theoretical Investigation of the Structural, Spectroscopic and Optical Properties of Adenine

Abstract

The structural, spectroscopic (IR, NMR and UV-Vis) and optical properties of adenine (6-aminopurine, C₅H₅N₅) are investigated theoretically using HF/DFT hybrid approach B3LYP. The calculated results are compared with available experimental data. The optimized bond distances and bond angles are converged within ±0.01 Å and ±0.8° with respect to the experimental values. The investigation of ¹H NMR chemical shift spectra of the aromatic C-H protons shows that the maximum deviation of the calculated chemical shift is ~ 0.53 ppm compared to the experimental data. The calculated vibrational spectra analysis shows four distinct IR active mode of vibrations which are assigned as scissoring vibration of –NH₂, symmetric stretching vibration of –NH₂, free –NH vibration and anti-symmetric stretching vibration of –NH₂, respectively. The electronic and optical properties are calculated by Time Dependent Density Functional Theory (TD-DFT) approach. A reasonable agreement is obtained for the calculated optical absorption energy with the experimental value.