Electronic Structure Explanation for the Structure and Reactivity of di- n -Butyltin(IV) Derivative of Glycylphenylalanine

The density functional theory (DFT)-based quantum-chemical calculations have been performed on di- n -butyltin(IV) derivative of glycylphenylalanine (H 2 L) using the Gaussian 09 software package. The molecular geometry of n -Bu 2 SnL was optimized at B3LYP/6-31G(d,p)/LANL2DZ(Sn) level of theory without any symmetry constraint. The harmonic vibrational frequencies were computed at the same level of theory to find the true potential energy surface (PES) minima. The various geometrical and thermochemical parameters for the studied complex are obtained in the gas phase. The atomic charges at all the atoms were calculated using Mulliken Population Analysis, Hirshfeld Population Analysis and Natural Population Analysis. The charge distribution within the studied complex is explained on the basis of molecular electrostatic potential maps, the frontier molecular orbital analysis and conceptual-DFT-based reactivity (global as well as local) descriptors, using the finite difference approximation method. The nature of O–Sn, N–Sn, N → Sn and C–Sn bonds is discussed in terms of the conceptual-DFT-based reactivity descriptors. The structural analysis of the studied complex has been carried out in terms of the selected bond lengths and bond angles. The structural and atomic charge analysis suggests a distorted trigonal bipyramidal arrangement consisting of negatively charged centres around the positively charged central Sn atom.