ABSTRACT
A quantum chemical perspective of 31 structures contains electron acceptors: ASCl3 (arsenic trichloride), PCl3 (phosphorous trichloride) and NCl3 (nitrogen trichloride); forming non-covalent bond with various nitrogen-based electron donors that resulted in pnicogen bonds, AS...N, P...N and N...N were calculated at M062X/def2-QZVP level of theory. Besides the above method, MP2/def2-QZVP and CCSD(T)/def2-QZVP level of theories have also been analysed to have in depth knowledge about the bonds formed. The nature of the bonds was assumed from the electrostatic potential evaluated for all the monomers, where σ hole is positive for all the monomers. The strongest pnicogen bonds are ASCl3-NF2H, PCl3-NCH3CH3CH3 and NCl3-NCH3CH3CH3 having interaction energies as -4.15, -11.58 and -3.25 kcal/mol, respectively, at MP2/def2-QZVP level of theory. Further at CCSD(T)/def2-QZVP level of theory, ASCl3-NF2H and NCl3-NCH3CH3CH3 are found to be the most stable with interaction energies as -3.53 and -2.45 kcal/mol, respectively. The potential energy surface scan was performed for all the stable complexes in order to confirm the existences of energies are true minima. Moreover to confirm the halogen and pnicogen bonds, AIM analysis was carried out. The results from the above factors of pnicogen bond will help crystal growth, material science and engineering community to explore novel materials, which abide for modernization. Graphical abstract PCl3-NCH3CH3CH3 complex with 2.61 Å and pnicogen angle of 178.54° is strong, and interaction energy is -11.58 kcal/mol. Electron donors - ASCl3, PCl3 and NCl3 and electron acceptors -NCH3CH3CH3, NH3C2 and NHCO have strong electrostatic contribution. High and low values of (ρ) ∇2(ρ) reveal the strong and weak pnicogen bond. Schematic representation of acceptors surrounded by its donors and Electrostatic Potential map.
ABSTRACT
The present study aims to spotlight on the strength of interaction between different fatty acids with the Bovine-lactoglobulin (LGB) protein side chains along with the crystal water molecules at M062X/def2-QZVP level of theory. To analyse the role of carboxylic acid and its interaction with side chains and to reveal the significance of carboxylic acid, it was replaced by Acyl chloride (COCl), Acyl Bromide (COBr) and Acyl-Fluorine (COF) group and COS group. The ligands are linear with a straight and branched chain of carbon atoms, but extended methyl group make the ligand bend resulting in non-planar geometry. The least and highest band gap energy reveals the conductivity properties of ligands. 3UEW, the Palmitic acid is well-built owing to the interaction with the amino acid side chains Lys 69 and Glu 62 resulting in interaction energy of -124.98kcal/mol. 3D-NCIplot isosurface map and 2D-NCIplot graph plays a key role to confirm and analyse the occurrence of various non covalent interactions. The overall analysis of the fatty acids implies the fact that depending on the aliphatic chain length, the carboxyl group was capable of positioning favourable binding site.
