Ruthenium(II) 1,4,7-trithiacyclononane complexes of curcumin and bisdemethoxycurcumin: Synthesis, characterization, and biological activity

Two cationic ruthenium(II) 1,4,7-trithiacyclononane ([9]aneS3) complexes of curcumin (curcH) and bisdemethoxycurcumin (bdcurcH), namely [Ru(curc)(dmso-S)([9]aneS3)]Cl (1) and [Ru(bdcurc)(dmso-S)([9]aneS3)]Cl (2) were prepared from the [RuCl2(dmso-S)([9]-aneS3)] precursor and structurally characterized, both in solution and in the solid state by X-ray crystallography. The corresponding PTA complexes [Ru(curc)(PTA)([9]aneS3)]Cl (3) and [Ru(bdcurc)(PTA)([9]aneS3)]Cl (4) have been also synthesized and characterized (PTA = 1,3,5-triaza-7-phosphaadamantane). Bioinorganic studies relying on mass spectrometry were performed on complexes 1–4 to assess their interactions with the model protein lysozyme. Overall, a rather limited reactivity with lysozyme was highlighted accompanied by a modest cytotoxic potency against three representative cancer cell lines. The moderate pharmacological activity is likely connected to the relatively high stability of these complexes.