Bismuth(III) saccharinate and thiosaccharinate complexes and the effect of ligand substitution on their activity against helicobacter pylori

Andrews, Philip C.;Ferrero, Richard L.;Forsyth, Craig M.;Junk, Peter C.;Maclellan, Jonathan G.;Peiris, Roshani M.

Abstract

Five bismuth(III) saccharinate and thiosaccharinate complexes, [Ph2Bi(sac)]∞1, [Bi(sac)3]n2, [Ph2Bi(tsac)]∞4, [PhBi(tsac)2]n5, [Bi(tsac)3]n6 (sacH = saccharin, tsacH = thiosaccharin), have been synthesized and fully characterized. The tendency for ligand redistribution in [Ph2Bi(sac)]∞ has been investigated in solution by NMR spectroscopy. The structures of [Ph2Bi(sac)]∞1 and [Ph2Bi(tsac)]∞4 have been confirmed by X-ray crystallography. In Ph2Bi(sac) the sac ligand is bound to a four-coordinate bismuth center via its imino nitrogen atom with an accompanying long-range Bi–O interaction. However, in the structure of [Ph2Bi(tsac)]∞ the ligand is σ-bound through the exocyclic sulfur atom, giving a thiolate complex, confirming the more thiophilic nature of bismuth(III). Both complexes consist of polymeric chain structures with formally four-coordinated bismuth atoms. The complexes were assessed for their activity against H. pylori. The activity is both ligand dependent and sensitive to the degree of ligand substitution. The saccharinate complexes, 1 and 2, show activity comparable with standard tris-carboxylato bismuth(III) compounds, 6.25 μg/mL, while the activity of the thiolato complexes, 4–6, increases dramatically on increasing the number of thiolate groups from one to three (range 50–6.25 μg/mL). Saccharin, thiosaccharin, and BiPh3 were found to be inactive.

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Organometallics

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1520-6041

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American Chemical Society

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DOI

10.1021/om2008869