A Density Functional Theory (DFT) Study on Di-n-Butyltin(IV) Derivative of Glycyltryptophane

The density functional theory (DFT) based quantum-mechanical calculations have been performed on di-n-butyltin (IV) derivative of glycyl-tryptophane (H₂L) using the Gaussian09 software package. The molecular geometry of n-Bu₂SnL was optimized with B3LYP functional with the standard 3-21G basis set for all the atoms, except the tin (IV) atom which was described by LANL2DZ basis set along with the effective core potential, 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 thermo chemical parameters for n-Bu₂SnL have been obtained in gas phase and in the solvent field. 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 and conceptual-DFT based reactivity (global as-well-as local) descriptors, using the finite difference approximation method. The calculated parameters suggest a distorted tetrahedral geometry around the central Sn atom. 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 vibrational analysis of characteristic infrared vibrational frequencies of the studied complex has also been carried out.