Theoretical insights on Organotin (IV)-protein interaction: Density Functional Theory (DFT) studies on di-n-butyltin(IV) derivative of Glycylvaline

Abstract

The density functional theory (DFT) based quantum-mechanical calculations have been performed on di-n-butyltin(IV) derivative of glycyl-valine using the Gaussian09 software package. The ground state optimization of the possible trigonal bipyramidal structure was carried out using 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 charge distribution within the dipeptide and its di-nbutyltin(IV) derivative was calculated using Mulliken population analysis, Hirshfeld population analysis and natural bond orbital analysis. The frontier molecular orbital analysis was carried out to calculate the energies of highest occupied molecular orbital (EHOMO) and lowest unoccupied molecular orbital (ELUMO). The conceptual-DFT based global reactivity descriptors such as, electronic chemical potential, electronegativity, chemical hardness, global softness and electrophilicity index have been obtained for the dipeptide and its di-n-butyltin(IV) derivative using the frontier molecular orbital analysis. The nature of O-Sn, N-Sn, N→Sn and C-Sn bonds is discussed in terms of the Mulliken population analysis and natural bond orbital analysis. The structural analysis of the dipeptide and its di-nbutyltin(IV) derivative has been carried out in terms of the selected bond lengths and bond angles. In order to explain the formation of the studied derivative, the vibrational analysis of its characteristic infrared vibrational frequencies has also been carried out.