Zn(ii) and Cu(ii) complexes containing bioactive O,O-chelated ligands: Homoleptic and heteroleptic metal-based biomolecules.

Historically, many useful drugs have been developed from natural sources and their mechanisms of action deeply investigated for therapeutic applications. Recently, the interaction between pharmacologically active biomolecules and transition metal ions has opened the way to the construction of new drugs, where the unique properties of metal complexes are combined with the specific mechanisms of action of the coordinated bioligands of natural extraction. In this context, this perspective summarizes some recent research studies devoted to the development of new metal-based drugs containing Zn(ii) or Cu(ii) metal ions.

Improving the bioactivity of Zn(II)-curcumin based complexes.

New Zn(II)-curcumin based heteroleptic complexes (1-5) have been synthesized and fully characterized, with the aim to improve the bioactivity of the precursor derivative [(bpy-9)Zn(curc)Cl] (A), a potentially intercalating antitumor agent recently reported. Some structural changes have been made starting from the reference complex A, in order to introduce new functionalities, such as electrostatic and/or covalent interactions. In particular, keeping the same N,N chelating ligand, namely bpy-9, two completely different Zn(II) species have been obtained: a tetracoordinated Zn(II) cation with tetrafluoroborate as counterion (1) and a dimeric neutral complex in which the sulfate anion acts as a bridging group through two Zn(II) centres (2).

Non-classical anticancer agents: on the way to water soluble zinc(II) heteroleptic complexes.

Two new heteroleptic Zn(II) complexes of the 4,4'-bis(hydroxymethyl)-2,2'-bipyridine have been synthesized by using different stoichiometric ratios of tropolone. In an attempt to induce the formation of metal complex co-crystals, liquid assisted solid state reaction followed by solvent crystallization has been conducted by using the new Zn(II) tropolonate derivatives 1 and 2 with saccharin. The novel Zn(II) species obtained exhibits different structures and properties with respect to their precursors, due to a hydrogen exchange between saccharin and the tropolonate coordinated ligand.