Half-sandwich type rhodium(iii)–aminohydroxamate complexes: the role of the position of the amino group in metal ion binding12. (28th March 2018)

• Record Type: Journal Article
• Authors: Parajdi-Losonczi, Péter László; Buglyó, Péter; Skakalova, Hana; Kasparkova, Jana; Lihi, Norbert; Farkas, Etelka
• Is Part Of: New journal of chemistry. Volume 42:Number 10(2018)
• Page Start: 7659
• Page End: 7670
• Publication Date: 2018-03-28
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c7nj04711h
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Relative order of the pH-dependent conditional stability of the hydroxamate type (O, O) and (Namino, Nhydroxamato ) chelates determines the coordination modes in the various mono- and dinuclear complexes of [(η 5 -Cp*)Rh III (H2 O)3 ] 2+ with α-, β- and γ-aminohydroxamic acids. Abstract : Complex formation equilibria between [(η 5 -Cp*)Rh III (H2 O)3 ] 2+ and aminohydroxamic acids (L-2-amino- N -hydroxyacetamide (α-alahaH), 3-amino- N -hydroxypropanamide (β-alahaH) and 4-amino- N -hydroxybutanamide (GABAha, γ-abhaH)) having the primary amino group in different chelatable positions relative to the hydroxamic function were studied using pH-potentiometric, 1 H NMR and ESI-MS methods and the formation constants of the complexes present in aqueous solution are reported. The relative order of the pH-dependent conditional stability of the hydroxamate type (O, O) and (Namino, Nhydroxamato ) chelates was found to determine to a great extent the coordination modes both in the mono- and various dinuclear species formed. While with α-alaha −, a 5-membered (N, N) chelated mononuclear complex predominates, with β-alaha − in a wide pH-range, very stable dinuclear cluster ions exist. With γ-abha −, in the most stable complexes, two ligands (in reverse variation) link two half-sandwich cations, coordinating each ligand via the hydroxamate chelate to one metal centre, while via the amino-N to the other one. This arrangement seems to be further stabilized by a hydrogen bond as DFT calculations support the extra stabilization effect of internal H-bonding in [{(η 5 -Cp*)Rh III }2 H−1 (γ-abha)2 ] + . The synthesis, spectral (NMR and IR) and MS characterization of a novel complex with an iridium analogue, [(η 5 -Cp*)Ir III (α-alaha)Br] (1 ) is also described. This complex was tested for its in vitro cytotoxicity using human-derived cancer cell lines (A2780, HeLa, DU-145, A549, and MCF-7) and showed insignificant anti-proliferative activity in the micromolar concentration range.