Organogold(III) metallacyclic chemistry. Part 4. Synthesis, characterisation, and biological activity of gold(III)-thiosalicylate and -salicylate complexes

The silver(I) oxide mediated reactions of the gold(III) dichloride complex [{C₆H₃(CH₂

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uCl₂] 2a with thiosalicylic or salicylic acid gives the respective complexes [{C₆H₃(CH₂

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)-2}] 3a (X=S) or 6b (X=O), containing chelating thiosalicylate or salicylate dianion ligands. X-ray studies show that for the thiosalicylate system, the thiosalicylate sulfur atom is trans to the N,N-dimethylamino group, whereas in the structure of the salicylate complex, it is the carboxylate group that is trans to NMe₂. Both complexes show puckered metallacycles in the solid state. Electrospray mass spectrometry (ESMS) shows strong [M+H]⁺ and [2M+H]⁺ ions for both the gold-thiosalicylate and -salicylate complexes, and these ions possess a high stability towards cone voltage-induced fragmentation. ESMS was also used to identify a minor impurity, the bis(cyclo-aurated) cationic complex [A

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Me₂)-2-(OMe)-5}2]⁺ in the starting dihalide complex 2a and in the product 3a. This complex can be formed by reaction of Me₄N[AuCl₄] with 2 equivalents of the organomercury precursor [Hg{C₆H₃(CH₂NMe₂)-2-(OMe)-5}Cl]. The biological (antitumour, antimicrobial and antiviral) activities are also reported, and these reveal the complexes have moderate to high anti-tumour, antibacterial and antifungal activity.