Spectroscopic and molecular electronic property investigation of 2-phenylpyrimidine-4, 6-diamine via 1H NMR, UV–vis, FT-Raman, FT-IR, and DFT approach

Abstract

Herein, 2-phenylpyrimidine-4, 6-diamine (PPD) was selected to extensively investigate its experimental, spectroscopic (FT-IR, FT-Raman, UV–vis, and 1H NMR) and molecular electronic properties based on first principle density functional theory (DFT) and time-dependent density functional theory (TD-DFT) in gas and solutions. All computational calculations of the studied structure was performed at the B3LYP/6–311++G(d,p) theoretical level. A detailed vibrational energy distribution analysis of the vibrational frequencies of PPD was also investigated in gas and different solvents and appropriately compared with the experimental data. Also, changes in the spectroscopic responsiveness, absorptivity and stability of the studied structure in different solvents (water, ethanol, and chloroform) were equally considered to appraise and comprehend any changes in properties with changes in solvent permittivity. Molecular electronic properties such as FMO, NBO and NLO were as well computed in different solvents to understand the reactivity, stabilization mechanism and optical activity of the studied molecule. The NH2 stretching and bending deformations were calculated and assigned between 3589 and 3707 cm−1, and 1576–1646 cm−1 respectively. Similarly, other functional groups and vibrations were assigned as appropriate. These peaks were observed to be red shifted with solvent permittivity and polarity. A comparison of the experimental frequencies and computed wavenumbers showed excellent conformity. The theoretically computed geometric parameters were able to replicate the experimentally obtained data to a greater extent. All computations prompt PPD to be stable and more reactive in polar solvents than non-polar solvents and suggest its suitability in diverse applications .