Synthesis, crystal structure, in vitro anticholinesterase activity, molecular docking and DFT investigation of three 1,10-phenanthroline-tin(IV) complexes

Abstract

This work describes the synthesis, the crystal structure and the properties of three tin complexes derivatives of 1,10-phenanthroline, namely C24H19N3SnCl2 (C1), C24H20N4SnCl2 (C2) and C27H22N4SnCl2 (C3). Their structures were elucidated by X-ray diffraction, IR and NMR (1H &13C). The in vitro anticholinesterase activity was investigated and compared to docking findings. The obtained results showed that the C2 complex presents the closest IC50 value (10.99±0.34 μM) to that of galantamine (4.14±0.07 μM) and corroborated by the docking results, where C2 and C1 showed a score of 54.08, 51.32 for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity, respectively. The optimized structures obtained by density functional theory (DFT) gave comparable geometrical parameters around the tin(IV) cation of hexacoordination environment. The computed HOMO-LUMO gaps are large predicting stable compounds. The natural population analysis attributes negative charges of chlorine, carbon and nitrogen atoms directly bound to the tin(IV) cation. However, the natural charges of tin(IV) of +1.63 in both C1 and C2 compounds are lower than +1.74 calculated for C3, suggesting different electron transfers. The FMOs localizations and Fukui functions predict that C1 and C2 behave differently from C3 with regard to the reactivity towards protein targets, in agreement with the experimental data and the molecular docking results.