DNA binding, DNA hydrolase and phosphatase like activity of new polyaza macrobicyclic binuclear copper(II), nickel(II) and zinc(II) complexes

Mapping the working route of phosphate monoester hydrolysis catalyzed by copper based models with special emphasis on the role of oxoanions by experimental and theoretical studies

The mechanistic pathway of phosphate-ester bond hydrolysis with special emphasis on the role of oxoanions was explored by experimental and theoretical study.

Dinuclear metal(ii)-acetato complexes based on bicompartmental 4-chlorophenolate: syntheses, structures, magnetic properties, DNA interactions and phosphodiester hydrolysis

A series of dinuclear metal(ii)-acetato complexes: [Ni2(μ-L(Cl)O)(μ2-OAc)2](PF6)·3H2O (1), [Ni2(μ-L(Cl)O)(μ2-OAc)2](ClO4)·CH3COCH3 (2), [Cu2(μ-L(Cl)O)(μ2-OAc)(ClO4)](ClO4) (3), [Cu2(μ-L(Cl)O)(OAc)2](PF6)·H2O (4), [Zn2(μ-L(Cl)O)(μ2-OAc)2](PF6) (5) and [Mn2(L(Cl)-O)(μ2-OAc)2](ClO4)·H2O (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) complexes 1, 2, 5 and 6, whereas with Cu(ii) complexes a five-coordinate species was obtained with 4, and mixed five- and six-coordinate geometries with a doubly bridged dimetal core were observed in 3. The magnetic properties of complexes 1-4 and 6 were studied at variable temperatures and revealed weak to very weak antiferromagnetic interactions in 1, 2, 4 and 6 (J = -0.55 to -9.4 cm(-1)) and ferromagnetic coupling in 3 (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 complexes 1-5 with supercoiled plasmid ds-DNA did not show any pronounced nuclease activity, but Ni(ii) complexes 1 and 2 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 complexes 1, 3, and 5 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 kcat/KM (kcat = catalytic rate constant, KM = 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.

Remarkable reactivity of alkoxide/acetato-bridged binuclear copper(II) complex as artificial carboxylesterase

Bromo-containing binuclear Schiff base copper(II) complex, Cu₂L(OAc), with an alkoxo/acetato-bridged moiety was employed as a model of carboxylesterases to promote the hydrolytic cleavage of p-nitrophenyl picolinate (PNPP). Furthermore, the reactivity of a mononuclear complex (CuHL) was evaluated for comparing it with that of binuclear one. The results reveal that the as-prepared binuclear Cu₂L(OAc) efficiently accelerated the hydrolysis of PNPP, giving rise to excess four orders of magnitude rate enhancement in contrast to the un-catalyzed reaction. Cu₂L(OAc) represented an enzyme-like bell-shaped pH-responsive kinetic behavior. Moreover, the binuclear one is more reactive than its mononuclear analogue (CuHL) by two orders of magnitude. The total efficiency of Cu₂L(OAc) is about 61-fold than that of its mononuclear analogue, CuHL. In addition, a contrast experiment reveals that binuclear Cu₂L(OAc) displayed good activity in the hydrolysis of PNPP as well another active ester, i.e., S-2-benzothiazolyl 2-amino-alpha-(methoxyimino)-4-thiazolethiolacetate (AE-active ester). Noteworthyly, it was found that mononuclear one inspired more obvious rate enhancement in the hydrolysis of AE-active ester relative to PNPP hydrolysis. The estimated pK _a1 of bound water on the binuclear Cu₂L(OAc) using second derivative method (SDM) is relatively smaller than that for CuHL by a gap of about 0.8 pK unit, which facilitates the hydrolysis of PNPP. Four orders of magnitude rate enhancement was observed for the catalytic hydrolysis of p-nitrophenyl picolinate (PNPP) by one μ-alkoxide/acetato-bridged binuclear copper(II) complex under physiological conditions. Substrate specificity of the resulting binuclear complexes was observed for the hydrolysis of PNPP and AE-active ester.

Role of para-substitution in controlling phosphatase activity of dinuclear NiII complexes of Mannich-base ligands: experimental and DFT studies

Five dinuclear Ni^II complexes synthesized by Mannich reaction portray remarkable phosphatase activity where the tert-butyl complex exhibits the maximum reactivity.

Two new mixed copper(ii)–dipeptide complexes of N,N-donor heterocycle ligands: studies on their non-covalent DNA binding, chemical nuclease, antioxidant and anticancer activities

Two novel mononuclear mixed ligand copper(ii)-dipeptide complexes have been synthesized. The DNA interactions of the complexes were investigated. In addition, the antioxidant and antitumor activities of the complexes were evaluated.

Synthesis and crystal structure determination of a mononuclear cobalt(ii) complex derived from 4-(pyridin-4-ylmethoxy)-benzoic acid: evaluation of the DNA/protein interaction and photo-induced pBR322 DNA cleavage

New Co(ii)-based chemotherapeutic drug candidate was synthesized and thoroughly characterized by spectroscopic, analytical and single crystal X-ray techniques.

Nuclease activity and interaction studies of unsymmetrical binuclear Ni(ii) complexes with CT-DNA and BSA

A new series of binuclear Ni(ii) complexes have been synthesized and their BSA, DNA binding and nuclease activity have been evaluated.

Synthesis, characterization, and biological activities of two Cu(II) and Zn(II) complexes with one polyquinoline ligand

Two new complexes, [CuLCl]ClO4 (1) and [Zn2L2SO4(H2O)2](ClO4)2 (2) [L=N,N-bis(quinolin-2-ylmethyl)quinolin-8-amine], have been synthesized and structurally characterized. The interactions of two complexes with CT-DNA have been investigated by UV absorption, fluorescence spectroscopy, viscosity measurements and gel electrophoresis under physiological conditions. Results show that the complexes bind to CT-DNA with a moderate intercalative mode and exhibit efficient DNA cleavage activity on UV-A light of 365 nm. Furthermore, two complexes could quench the intrinsic fluorescence of BSA in a static quenching process based on BSA binding experiments. Notably, in vitro cytotoxicity study of two complexes on four human tumor cells lines (7404, HeLa, MCF-7, and HepG-2) indicate that both of them have the potential to act as effective anticancer drugs with low IC50 values.

Self-assembled Cu(ii) and Ni(ii) metallamacrocycles formed from 3,3,3′,3′-tetrabenzyl-1,1′-aroylbis(thiourea) ligands: DNA and protein binding studies, and cytotoxicity of trinuclear complexes

The synthesis and characterization of metallamacrocyclic square planar Ni(ii) and Cu(ii) complexes and the interaction of cytotoxic trinuclear complexes with CT DNA and BSA protein are described.

DNA/BSA binding, DNA cleavage and electrochemical properties of new multidentate copper(ii) complexes

A new series of multidentate copper(ii) complexes [Cu(L¹⁻⁵)](ClO₄) (1–5) were synthesized and characterized for their DNA/BSA binding, DNA cleavage, cytotoxic properties and antimicrobial activities.