Dinuclear metal(ii)-acetato complexes based on bicompartmental 4-chlorophenolate: syntheses, structures, magnetic properties, DNA interactions and phosphodiester hydrolysis. Issue 32 (1st August 2016)

• Record Type: Journal Article
• Authors: Massoud, Salah S.; Ledet, Catherine C.; Junk, Thomas; Bosch, Simone; Comba, Peter; Herchel, Radovan; Hošek, Jan; Trávníček, Zdeněk; Fischer, Roland C.; Mautner, Franz A.
• Is Part Of: Dalton transactions. Volume 45:Issue 32(2016)
• Page Start: 12933
• Page End: 12950
• Publication Date: 2016-08-01
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt02596j
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Dinuclear Ni(ii )-, Cu(ii )-, Zn(ii )- and Mn(ii )-acetato complexes have been used in the cleavage of DNA and the hydrolysis of BDNPP. Abstract : A series of dinuclear metal(ii )-acetato complexes: [Ni2 (μ-L Cl O)(μ2 -OAc)2 ](PF6 )·3H2 O (1 ), [Ni2 (μ-L Cl O)(μ2 -OAc)2 ](ClO4 )·CH3 COCH3 (2 ), [Cu2 (μ-L Cl O)(μ2 -OAc)(ClO4 )](ClO4 ) (3 ), [Cu2 (μ-L Cl O)(OAc)2 ](PF6 )·H2 O (4 ), [Zn2 (μ-L Cl O)(μ2 -OAc)2 ](PF6 ) (5 ) and [Mn2 (L Cl -O)(μ2 -OAc)2 ](ClO4 )·H2 O (6 ), where L Cl O − = 2, 6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenolate, were synthesized. The complexes were structurally characterized by spectroscopic techniques and single crystal X-ray crystallography. Six-coordinate geometries with doubly bridged acetato ligands were found in Ni(ii ), Zn(ii ) and Mn(ii ) complexes1, 2, 5 and6, whereas with Cu(ii ) complexes a five-coordinate species was obtained with4, and mixed five- and six-coordinate geometries with a doubly bridged dimetal core were observed in3 . The magnetic properties of complexes1–4 and6 were studied at variable temperatures and revealed weak to very weak antiferromagnetic interactions in1, 2, 4 and6 ( J = −0.55 to −9.4 cm −1 ) and ferromagnetic coupling in3 ( J = 15.4 cm −1 ). These results are consistent with DFT calculations performed at the B3LYP/def2-TZVP(-f) level of theory. Under physiological conditions, the interaction of the dinculear complexes1–5 with supercoiled plasmid ds-DNA did not show any pronounced nuclease activity, but Ni(ii ) complexes1 and2 revealed a strong ability to unwind the supercoiled conformation of ds-DNA. The mechanistic studies performed on the interaction of the Ni(ii ) complexes with DNA demonstrated the important impact of the nickel(ii ) ion in the unwinding process. In combination with the DNA study, the phosphatase activity of complexes1, 3, and5 was examined by the phosphodiester hydrolysis of bis(2, 4-dinitrophenol)phosphate (BDNPP) in the pH range of 5.5–10.5 at 25 °C. The Michaelis–Menten kinetics performed at pH 7 and 10.7 showed that catalytic efficiencies k cat / K M ( k cat = catalytic rate constant, K M = substrate binding constant) decrease in the order: Ni(ii ), 1 > Zn(ii ), 5 > Cu(ii ), 3 . A similar trend was also observed with the turnover numbers at pH = 7. The results are discussed in relation to the coordination geometry and nature of the metal center as well as the steric environment imposed by the compartmental phenoxido ligand.