Computational spectroscopic and NLO activity studies ON 2-amino-4,6 dimethylpyrimidine, 2-amino benzoic acid and the effect of substituent groups

This study aims at the structural and spectral analysis of 2-amino-4, 6-dimethylpyrimidine, 2 aminobenzoic acid, along with the substitution of hydroxyl (-OH), amino (-NH2), methyl (-CH3) and methoxy (-OCH3) groups. The calculations were done using DFT with B3LYP/6-311G (d, p) level of theory. The natural bond orbital analysis was carried out to identify the delocalisation of charges that is taking place due to intramolecular interactions. The electronic properties, such as molecular electrostatic potential and Frontier molecular orbital analysis, were executed to identify the reactive site and charge transfer within the molecule. The potential energy scan was performed to identify the most stable conformer. The topological analysis, namely interaction region indicator, reduced density gradient, electron localisation function and localised orbital locator were carried out to determine the intermolecular hydrogen bonding. ELF and LOL have shown an illustrative proof of intra – and intermolecular charge transfer interaction; this raises the molecule's NLO activity. To show the non-linear optical active nature of the material, hyperpolarisability calculations were carried out. The second order hyperpolarisability of 2-amino-4,6 dimethylpyrimidine – 2,6-diamino benzoic acid was estimated to be 1087.127 e.s.u, proving the potential NLO application.