Synthesis, Spectral Analysis, and Structural Investigations of Tin (IV) and Organotin (IV) Complexes with Schiff Base Ligands: A Review

Abstract

The chemistry of tin(IV) and organotin(IV) complexes has garnered significant attention due to their intriguing structural diversity and wide spectrum of biological applications. In this study, novel tin(IV) and organotin(IV) complexes were synthesized using Schiff base ligands derived from salicylaldehyde and various primary amines. The synthesized ligands and their corresponding complexes were characterized through a combination of analytical and spectroscopic techniques including elemental analysis, infrared (IR), ultraviolet-visible (UV-Vis), proton and carbon-13 nuclear magnetic resonance (¹H and ¹³C NMR), and mass spectrometry. The IR spectral data confirmed the successful coordination of the azomethine nitrogen and phenolic oxygen atoms to the metal centers, as evidenced by characteristic shifts in ν(C=N) and ν(C–O) bands. NMR spectroscopy provided insights into the geometry and electronic environment around the tin atom, indicating the formation of tetra-, penta-, and hexa-coordinated species depending on the ligand and the organotin precursor used. UV-Vis spectra supported the presence of metal-ligand charge transfer transitions, consistent with the proposed coordination structures. The complexes exhibited significant stability in ambient conditions and demonstrated moderate to high solubility in common organic solvents.

Additionally, preliminary biological screening of the complexes revealed enhanced antimicrobial and cytotoxic properties in comparison to the free ligands, highlighting the potential pharmacological relevance of these metal complexes. The observed increase in biological activity upon complexation is attributed to the chelation effect, which improves lipophilicity and cellular uptake. These findings contribute to the growing field of organometallic medicinal chemistry and underscore the potential of tin(IV) coordination compounds in therapeutic applications. Further work involving detailed biological assessments and crystallographic studies is ongoing to explore structure–activity relationships.