Synthesis and characterization of bis[dicarboxylatotetraorganodistannoxane] units involving 5-[( E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids: An investigation of structures by X-ray diffraction, NMR, electrospray ionisation MS and assessment of in vitro cytotoxicity

Abstract

Reactions of 5-[( E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L 1HH′: R = H; L 2HH′: R = 2′-CH 3; L 3HH′: R = 3′-CH 3; L 4HH′: R = 4′-CH 3; L 5HH′: R = 4′-Cl; L 6HH′: R = 4′-Br) with n Bu 2SnO in a 1:1 molar ratio yielded complexes of composition {[ n Bu 2Sn(LH)] 2O} 2. The complexes have been characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119 m Sn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of {[ n Bu 2Sn(L 1H)] 2O} 2 ( 1), {[ n Bu 2Sn(L 4H)] 2O} 2 ( 4), {[ n Bu 2Sn(L 5H)] 2O} 2 ( 5) and {[ n Bu 2Sn(L 6H)] 2O} 2 ( 6) were determined. The compounds are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn 4O 2 core in which two μ 3-oxo O-atoms connect an Sn 2O 2 ring to two exocyclic Sn-atoms. The four carboxylate ligands display two different modes of coordination where both modes involve bridging of two structurally distinct Sn-atoms. The solution structures were confirmed by 119Sn NMR spectroscopy by observing two tin resonances in compounds 1, and 4– 6. The observed difference between the two tin resonances was about 3 ppm while the differences in 13C resonances were even smaller. Compounds {[ n Bu 2Sn(L 2H)] 2O} 2 ( 2) and {[ n Bu 2Sn(L 3H)] 2O} 2 ( 3) undergo a very complex exchange processes in deuteriochloroform solution. The in vitro cytotoxic activity of compounds 1 and 4 against WIDR, M19 MEL, A498, IGROV, H226, MCF7 and EVSA-T human tumour cell lines is reported.