A quantum chemical perspective on the potency of electron donors and acceptors in pnicogen bonds (AS...N, P...N, N...N).

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.