New mononuclear copper(II) complex based on a salen derivative ligand with an unusual coordination and its catecholase activity

The new mononuclear copper(II) complex [CuII(H2LDA)(ClO4)](ClO4) (1) ([H2LDA = N,N′-[bis-(2-hydroxy-3- formyl-5-methylbenzyl)(dimethyl)]-ethylenediamine])with an unusual coordination mode of a salen derivative ligand is reported. The most interesting feature of 1 is that the ligand is doubly protonated and presents significant intermolecular π-stacking interactions, contributing to the dimer structure stabilization in the solid state and in CH3CN and methanolic solutions. The complex was characterized by X-ray crystallography and shows catecholase-like activity in the oxidation of the substrate 3,5-di-tert-butylcatechol (3,5-dtbc), with the formation of H2O2, which kinetic parameters are similar to those observed in conventional dinuclear bridged CuII complexes.FAPESCCAPESINCT-Catális

Synthesis, Structure, and Phosphatase-Like Activity of a New Trinuclear Gd Complex with the Unsymmetrical Ligand H(3)L As a Model for Nucleases

The new trinuclear gadolinium complex [Gd(3)L(2)(NO(3))(2)(H(2)O)(4)]NO(3)center dot 8H(2)O (1) with the unsymmetrical ligand 2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-bis(2-hydroxy-2-oxoethyl)aminomethyl] phenol (H(3)L) was synthesized and characterized. The new ligand H(3)L was obtained in good yield. Complex I crystallizes in an orthorhombic cell, space group Pcab. Kinetic studies show that complex 1 is highly active in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate (K(m) = 4.09 mM, V(max) = 2.68 x 10(-2) mM s(-1), and k(cat) = V(max)/[1] = 0.67 s(-1)). Through a potentiometric study and determination of the kinetic behavior of 1 in acetonitrile/water solution, the species present in solution could be identified, and a trinuclear monohydroxo species appears to be the most prominent catalyst under mild conditions. Complex 1 displays high efficiency in DNA hydrolytic cleavage, and complete kinetic studies were carried out (K(m) = 4.57 x 10(-4) M, K(cat)` = 3.42 h(-1), and k(cat)`/K(m) = 7.48 x 10(3) M(-1) h(-1)). Studies with a radical scavenger (dimethyl sulfoxide, DMSO) showed that it did not inhibit the activity, indicating the hydrolytic action of 1 in the cleavage of DNA, and studies on the incubation of distamycin with plasmid DNA suggest that 1 is regio-specific, interacting with the minor groove of DNA.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq[PNPD-151665/2008-7]INCT-cataliseINCT-cataliseINCT-Biologia Estrutural e BioimagemINCT-Biologia Estrutural e BioimagemFundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina (FAPESC)FAPES

An Unprecedented FeIII(μ-OH)ZnII Complex that Mimics the Structural and Functional Properties of Purple Acid Phosphatases

This communication reports the synthesis and X-ray structure of the first mixed-valence FeIIIZnII complex containing the FeIII(μ-OH)ZnII structural unit. Based on the structure, physicochemical solution studies, and the catalytic properties toward the hydrolysis of the diester 2,4-bis(dinitrophenyl)phosphate (BDNPP), it is proposed that complex 1 employs a hydrolytic mechanism similar to that proposed for red kidney bean purple acid phosphatase, including a nucleophilic attack by the terminal, FeIII-bound hydroxide and the concomitant release of 2,4-dinitrophenolate. Furthermore, it is demonstrated that the μ-hydroxo group in the {FeIII(μ-OH)(μ-ROPO3)ZnII} intermediate is unable to hydrolyze the monoester 2,4-dinitrophenylphosphate (DNPP), which suggests that the μ-hydroxo group is a significantly poorer nucleophile than the terminally FeIII-bound OH- group

Second-coordination-sphere effects increase the catalytic efficiency of an extended model for FeIIIMII purple acid phosphatases

Herein we describe the synthesis of a new heterodinuclear FeIIICuII model complex for the active site of purple acid phosphatases and its binding to a polyamine chain, a model for the amino acid residues around the active site. The properties of these systems and their catalytic activity in the hydrolysis of bis(2,4-dinitrophenyl)phosphate are compared, and conclusions regarding the effects of the second coordination sphere are\ud drawn. The positive effect of the polymeric chain on DNA hydrolysis is also described and discussed.Instituto Nacional de Ciência e Tecnologia de Catálise em Sistemas Moleculares e Nanoestruturados (INCT - CMN)Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem (INBEB)CNP

Catecholase and DNase activities of copper(II) complexes containing phenolate-type ligands

Three new homodinuclear complexes containing substituted phenolate-type ligands based on the N(5)O(2) donor (2-(N,N-Bis(2-pyridylmethyl)aminomethyl)-6-(N`,N`-(2-hydroxybenzyl)(2-pyridylmethyl))aminomethyl)-4-methylphenol (H(2)L-H) were synthesized and characterized by X-ray crystallography. Potentiometric titration studies in 70% (v/v) aqueous ethanol show that all three complexes exhibit a common {Cu(II)(mu-phenoxo)(mu-OH)Cu(II)(OH)} core in solution. Kinetic studies on the oxidation reaction of 3,5-di-tert-butylcatechol revealed that the catalytic activity of the metal complexes increases toward the ligand containing an electron-donating group. In addition, these complexes also carried out DNA cleavage by hydrolytic and oxidative pathways. Copyright (C) 2010 John Wiley & Sons, Ltd

New La(III) Complex Immobilized on 3‑Aminopropyl-Functionalized Silica as an Efficient and Reusable Catalyst for Hydrolysis of Phosphate Ester Bonds

Described herein is the synthesis, structure, and monoesterase and diesterase activities of a new mononuclear [La^III(L¹)­(NO₃)₂] (<b>1</b>) complex (H₂L¹ = 2-bis­[{(2-pyridylmethyl)-aminomethyl}-6-[<i>N</i>-(2-pyridylmethyl) aminomethyl)])-4-methyl-6-formylphenol) in the hydrolysis of 2,4-bis­(dinitrophenyl)­phosphate (2,4-BDNPP). When covalently linked to 3-aminopropyl-functionalized silica, <b>1</b> undergoes disproportionation to form a dinuclear species (<b>APS-1</b>), whose catalytic efficiency is increased when compared to the homogeneous reaction due to second coordination sphere effects which increase the substrate to complex association constant. The anchored catalyst <b>APS-1</b> can be recovered and reused for subsequent hydrolysis reactions (five times) with only a slight loss in activity. In the presence of DNA, we suggest that <b>1</b> is also converted into the dinuclear active species as observed with <b>APS-1</b>, and both were shown to be efficient in DNA cleavage

Second-Coordination-Sphere Effects Increase the Catalytic Efficiency of an Extended Model for Fe^IIIM^II Purple Acid Phosphatases

Herein we describe the synthesis of a new heterodinuclear Fe^IIICu^II model complex for the active site of purple acid phosphatases and its binding to a polyamine chain, a model for the amino acid residues around the active site. The properties of these systems and their catalytic activity in the hydrolysis of bis­(2,4-dinitrophenyl)­phosphate are compared, and conclusions regarding the effects of the second coordination sphere are drawn. The positive effect of the polymeric chain on DNA hydrolysis is also described and discussed