Triorganotin(IV) complexes of Schiff base derived from 1,2,4-triazole moiety: Synthesis, spectroscopic investigation, DFT studies, antifungal activity and molecular docking studies

Abstract

New triorganotin (IV) complexes of Schiff base (E)-4-amino-3-(2-(4-hydroxybenzylidene)hydrazinyl)-1H-1,2,4-triazole-5(4H)-thione (HL) with general formula R3SnL (where L is the monoanion of Schiff base (HL) and R = n-Bu(1)/Ph(2)) have been synthesized and thoroughly characterized by using analytical and multi-spectroscopic techniques such as FT-IR/Raman, NMR (1H, 13C, 119Sn), 2D-HMQC, ESI-MS spectrometry. A distorted tetrahedral geometry around tin have been proposed for these organotin (IV) derivatives in which Schiff base ligand acts as monoanionic monodentate coordinating through the Ohydroxyl. A density functional theory (DFT) based quantum chemical calculations have been performed at B3LYP/6-31G (d,p)/Def2-SVP(Sn) level of theory. The atomic charges have been calculated at the selected atoms, and the reactive sites have been assigned on the surface of the molecules through molecular electrostatic potential (MEP) map. In order to obtain an insight into the structure and reactivity behaviour, the conceptual-DFT based global and local reactivity descriptors and the frontier molecular orbital analysis was carried out to study the charge transfer within the complex. A comparative analysis of calculated vibrational frequencies with experimental vibrational frequencies was carried out and significant bands were assigned. The nature of O–Sn bonding is discussed in terms of the natural bond orbital (NBO) analysis. In vitro antifungal activity of the triorganotin (IV) complexes and Schiff base ligand were tested to explore their potential antifungal activity and the obtained bioactivity results were further validated by in Silico molecular docking studies.