Structural and solution studies of phenylbismuth(III) sulfonate complexes and their activity against Helicobacter pylori

Three bis-phenylbismuth sulfonates [Ph(2)Bi(O(3)SR)](infinity) (R = p-tolyl 1, mesityl 2 or S-(+)-10-camphoryl 3) have been synthesised and characterised. Their tendency for ligand redistribution in solution, and activity against the bacterium Helicobacter pylori have been investigated. The structures of 2 and 3 have been authenticated by X-ray diffraction crystallography. They are structurally very similar with polymeric helical chain structures composed of four coordinate Bi atoms which bridge between two sulfonate O atoms with near linear O-Bi-O bond angles. The two phenyl rings are cis to one another and trans to the stereochemically active lone pair. Upon dissolution of the pure compounds 1, 2 and 3, a ligand redistribution reaction occurs in which the mono-phenylbismuth bis-sulfonates, the bismuth tris-sulfonates and triphenylbismuth are formed. Two further complexes of general formula [PhBi(O(3)SR)(2)](infinity) (where R = p-tolyl 4, and mesityl 5) were thus obtained and their crystal structures determined. The presence of the single sulfonato ligand in compounds 1, 2 and 3 resulted in a dramatic increase in bacteriocidial activity towards H. pylori (MIC values of >= 6.25 mu g mL(-1)) relative to BiPh(3) (>64 mu g mL(-1)) and the sulfonic acids, which were essentially inactive.