A series of mononuclear nickel(II) complexes of Schiff-base ligands having N,N,O- and N,N,N-donor sites: Syntheses, crystal structures, solid state thermal property and catecholase-like activity

Guha, Averi; Banu, Kazi Sabnam; Das, Swapan K; Chattopadhyay, Taraprasad; Sanyal, Ria; Zangrando, Ennio; Das, Debasis

doi:10.1016/j.poly.2012.07.088

Cited by 36 publications

(9 citation statements)

References 23 publications

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“…The hydrogen atom (H6a) of the imidazalato nitrogen N(6a) forms bifurcated hydrogen bonds with the perchlorate oxygen atoms (O12 and O13). Such type of hydrogen bonds have been already investigated by earlier workers [80][81][82]. Moreover, the complexes are paired in the crystal about a center of symmetry giving rise to a double H-bond ( Fig.…”

Section: Structural Characterizationmentioning

confidence: 68%

Structure and antioxidant superoxide dismutase activity of copper(II) hydrazone complexes

et al. 2017

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Three new mixed ligand hydrazone complexes viz., [Cu(L)(neocuprin)]NO 3 .H 2 O 1, [Cu(L)(HL)]ClO 4 2 and [Cu 2 (2-(2-pyridyl)benzimidazole) 2 (L) 2 ]ClO 4 3 (L = N'-[(E)phenyl(pyridin-2-yl)methylidene]furan-2-carbohydrazide) have been synthesized by the biomimetic synthesis strategy and their structures were determined by single crystals X-ray analysis. The effect of differing contagious, as well as the rotational conformational versatility of HL, was demonstrated by the difference in structures of complexes 1-3. These complexes exhibited the antioxidant superoxide dismutase enzymatic activity. The geometry of copper(II) atom in complex 1 is distorted square pyramidal while in complexes 2 and 3 the geometries around copper(II) atoms are distorted octahedral. Magnetic measurements and epr spectroscopy of binuclear complex 3 have shown antiferromagnetic exchange interaction with a coupling constant (J) =-10.87 cm-1. Electronic and spectral properties of these newly synthesized hydrazone complexes (1-3) are interpreted by DFT and TDDFT calculations. The results reveal that molecular structures have significant effect on antioxidant superoxide activity. Such biological experimental values (antioxidant SOD activity data) are indicative of the promising application of these complexes into the bioinorganic chemistry of superoxide dismutase.

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Section: Structural Characterizationmentioning

confidence: 68%

Structure and antioxidant superoxide dismutase activity of copper(II) hydrazone complexes

et al. 2017

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“…Nickel(II) has very rich coordination chemistry owing to its inherent ability to adopt various geometries that are often interconvertible, and it is very well documented that such configurational or conformational changes are generally associated with color changes. − Interestingly, how a change in the coordination chemistry of nickel(II) may influence their catalytic property has not yet been properly addressed in the literature. Our group is continuously engaged in studying Schiff-base complexes of transition- and post-transition-metal ions, mainly as small synthetic analogues of metallobiosites like catechol oxidase, phosphatase, and cyt P-450 and as possible mimics of nucleases. − During our study to develop synthetic analogues of catechol oxidase, we synthesized a small dinuclear nickel(II) complex of 2,6-bis( N -ethylpiperazinyliminomethyl)-4-methylphenolate, and to our surprise, we observed an extraordinary catalytic activity of the complex to oxidize not only 3,5-di- tert -butylcatechol (3,5-DTBC) but also tetrachlorocatechol, a substrate that is very difficult to oxidize . Critical analysis revealed that the extra positive charge on the ligand backbone might be instrumental for such extraordinary activity.…”

Section: Introductionmentioning

confidence: 99%

A Combined Experimental and Theoretical Investigation on the Role of Halide Ligands on the Catecholase-like Activity of Mononuclear Nickel(II) Complexes with a Phenol-Based Tridentate Ligand

et al. 2013

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Three new mononuclear nickel(II) complexes, namely, [NiL(1)(H2O)3]I2·H2O (1), [NiL(1)(H2O)3]Br2·H2O (2), and [NiL(1)(H2O)3]Cl2·2H2O (3) [HL(1) = 2-[(2-piperazin-1-ylethylimino)methyl]phenol], have been synthesized and structurally characterized. Structural characterization reveals that they possess similar structure: [NiL(1)(H2O)3](2+) complex cations, two halide counteranions, and lattice water molecules. One of the nitrogen atoms of the piperazine moiety is protonated to provide electrical neutrality to the system, a consequence observed in earlier studies (Inorg. Chem. 2010, 49, 3121; Polyhedron 2013, 52, 669). Catecholase-like activity has been investigated in methanol by a UV-vis spectrophotometric study using 3,5-di-tert-butylcatechol (3,5-DTBC) as the model substrate. Complexes 1 and 2 are highly active, but surprisingly 3 is totally inactive. The coordination chemistries of 1 and 2 remain unchanged in solution, whereas 3 behaves as a 1:1 electrolyte, as is evident from the conductivity study. Because of coordination of the chloride ligand to the metal in solution, it is proposed that 3,5-DTBC is not able to effectively approach an electrically neutral metal, and consequently complex 3 in solution does not show catecholase-like activity. Density functional theory (DFT) calculations corroborate well with the experimental observations and thus, in turn, support the proposed hypothesis of inactivity of 3. The cyclic voltametric study as well as DFT calculations suggests the possibility of a ligand-centered reduction at -1.1 V vs Ag/AgCl electrode. An electron paramagnetic resonance (EPR) experiment unambiguously hints at the generation of a radical from EPR-inactive 1 and 2 in the presence of 3,5-DTBC. Generation of H2O2 during catalysis has also been confirmed. DFT calculations support the ligand-centered radical generation, and thus a radical mechanism has been proposed for the catecholase-like activity exhibited by 1 and 2. Upon heating, 2 and 3 lose water molecules in two steps (first lattice waters, followed by coordinating water molecules), whereas 3 loses four water molecules in a single step, as revealed from thermogravimetric analysis. The totally dehydrated species are red, in all cases having square-planar geometry, and have amorphous nature, as is evident from a variable-temperature powder X-ray diffraction study.

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“…There are only few reports where mononuclear nickel com-plexes have been studied for possible catecholase like activities. 29,30 It has been also indicated in some cases that extra positive charge on ligand induces higher activity towards catechol oxidation. 29,30 Herein, we report the synthesis and characterization of four new mononuclear nickel complexes [Ni(L 1 )]ClO 4 1a [HL 1 = 1-Phenyl-3-(2-piperazin-1-yl-ethylimino)-but-1-en-1-ol], [Ni(L 2 )]-ClO 4 1b [HL 2 = 4-((2-( piperazin-1-yl)ethyl)imino)pent-2-en-2-ol] [Ni(SCN) 3 (CH 3 OH)(aminoethylpiperazineH)] 2a and [Ni(DMSO) 4 -(aminoethylpiperazineH)](ClO 4 ) 3 2b.…”

Section: Introductionmentioning

confidence: 99%

“…29,30 It has been also indicated in some cases that extra positive charge on ligand induces higher activity towards catechol oxidation. 29,30 Herein, we report the synthesis and characterization of four new mononuclear nickel complexes [Ni(L 1 )]ClO 4 1a [HL 1 = 1-Phenyl-3-(2-piperazin-1-yl-ethylimino)-but-1-en-1-ol], [Ni(L 2 )]-ClO 4 1b [HL 2 = 4-((2-( piperazin-1-yl)ethyl)imino)pent-2-en-2-ol] [Ni(SCN) 3 (CH 3 OH)(aminoethylpiperazineH)] 2a and [Ni(DMSO) 4 -(aminoethylpiperazineH)](ClO 4 ) 3 2b. The interaction of complexes 1a and 1b with DNA, BSA and HSA have been also studied, which showed promising results with very high affinity towards DNA and albumin proteins.…”

Section: Introductionmentioning

confidence: 99%

Nickel(ii) complexes with a flexible piperazinyl moiety: studies on DNA and protein binding and catecholase like properties

et al. 2015

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Four new mononuclear Ni(ii) complexes [Ni(L(1))]ClO4 (), [Ni(L(2))]ClO4(), [Ni(SCN)3(CH3OH)(aminoethylpiperazineH)] (), and [Ni(DMSO)4(aminoethylpiperazineH)](ClO4)3()have been synthesized from two Schiff base ligands [L(1) = 1-phenyl-3-((2-(piperidin-4-yl)ethyl)imino)but-1-en-1-ol and L(2) = 4-((2-(piperazin-1-yl)ethyl)imino)pent-2-en-2-ol] by exploiting the flexibility of the piperazinyl moiety. Structural analysis reveals that and are square planar complexes with piperazine rings in boat conformations whereas hydrolysis of Schiff bases (L(1) and L(2)) occurs during formation of octahedral complexes ( and ) with piperazine rings in chair conformations. Screening tests were conducted to quantify the binding ability of complexes (, and ) towards DNA, BSA and HSA and it was found that square planar complexes ( and ) showed more effective binding properties over octahedral complex (). Furthermore, enzyme kinetic studies reflect that square planar complexes ( and ) are also effective in mimicking catecholase like activities over octahedral complex (). Among all the complexes, was found to be the most promising molecule among the series due to its large binding affinity towards different bio-macromolecules and higher T.O.N in the catechol oxidation reaction.

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A series of mononuclear nickel(II) complexes of Schiff-base ligands having N,N,O- and N,N,N-donor sites: Syntheses, crystal structures, solid state thermal property and catecholase-like activity

Cited by 36 publications

References 23 publications

Structure and antioxidant superoxide dismutase activity of copper(II) hydrazone complexes

Structure and antioxidant superoxide dismutase activity of copper(II) hydrazone complexes

A Combined Experimental and Theoretical Investigation on the Role of Halide Ligands on the Catecholase-like Activity of Mononuclear Nickel(II) Complexes with a Phenol-Based Tridentate Ligand

Nickel(ii) complexes with a flexible piperazinyl moiety: studies on DNA and protein binding and catecholase like properties

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