A versatile bioinspired metallocatalyst [Ni 2 L 2 (NCS)(Ac)(H 2 O) 0.5 (MeOH) 0.5 ]·1.25H 2 O (HL = 2-((E)-(2-(pyridin-2-yl)ethylimino)methyl)-4-chlorophenol) has been synthesized from a Schiff-base ligand and characterized as reported earlier (Sanyal et al., 2016). It portrays catecholase activity as an oxygen dependent enzymatic radical catalysis under completely aerobic conditions (λ max = 375 nm, ε = 1900 M −1 cm −1 ) against the model substrate 3,5-di-tert-butylcatechol (3,5-DTBC). Interestingly, Michaelis-Menten analysis of pseudo first-order reaction kinetics establishes that DMF medium provides a better catalytic pathway for catecholase activity (k cat = 2.8 × 10 −3 s −1 ) than acetonitrile (9.11 × 10 −4 s −1 ) under excess substrate conditions. Cell viability study, drug uptake assay, reactive oxygen species (ROS) formation, alteration of mitochondrial membrane potential (MMP), apoptosis study and DNA fragmentation demonstrates a significant dose dependent anti-leukemic activity on KG-1A (AML) and K562 (CML) cell lines. Notably, outstanding anti-bacterial property was also observed on multi-drug resistant E. coli and S. aureus bacteria. © 2016

Debasis Das

Chemistry

R SANYAL

S K DASH

P KUNDU

D MANDAL

S ROY

D DAS

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Inorganica Chimica Acta

Two &ldquo;end-off&rdquo; compartmental ligands, 2-formyl-4-chloro-6-N-ethylmorpholine-iminomethylphenol (HL1) and 2-formyl-4-methyl-6-N-ethylpyrrolidine-iminomethyl-phenol (HL2) have been designed and three complexes of Mn(II), one Mono-, one di- and other polynuclear, namely Mn(L1)(SCN)2(H2O)] (1), [Mn2(L1)(OAc)2](BPh4)] (2), and [Mn2(L2)(OAc)2(dca)]n(3) have been synthesized and structurally characterized. Variable temperature magnetic study of 2 and 3 have been performed and data analyses reveal that Mn centers are antiferromagetic coupled with J = - 9.15 cm-1 and J = - 46.89, respectively. Catecholase activity of all the complexes have been investigated using 3,5-di-tert-butyl catechol (3,5-DTBC). All are highly active with activity order on the basis of kcat value is 2&gt;1&gt;3. In order to unveil whether metal centered redox participation or radical pathway is responsible for the catecholase-like activity of the complexes detailed EPR and cyclic voltametric (CV) study have been performed. In addition to six line EPR spectrum characteristic to Mn(II) an additional peak at g~2 is observed when the EPR study is done with the mixture of 3,5-DTBC and catalyst, suggesting the formation of organic radical Page 1 of 31 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 19 November 2015. Downloaded by UNIVERSITY OF OTAGO on 20/11/2015 03:32:46. View Article Online DOI: 10.1039/C5DT03659C 2 most likely ligand centered. CV experiment with the mixture of 3,5-DTBC and catalyst reveals ligand centered reduction rather than reduction of Mn(II) to Mn(I). It is thus inferred that complexes 1-3 show catecholase-like activity due to radical generation.

Fulltext

Dalton Transactions

Mn(ii) complexes of different nuclearity: synthesis, characterization and catecholase-like activity

Four new dinuclear CuII complexes were synthesised from two Mannich-base ligands namely 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-chlorophenol (HL1) and 2-[bis(2- methoxyethyl)aminomethyl]-4-chlorophenol (HL2): [Cu2(L1)(OH)](ClO4)2.CH3OH (1), [Cu2(L2)2](ClO4)2.H2O (2), [Cu2(L2)2(NO3)2] (3) and [Cu2(L2)2(OAc)2].H2O (4) and well characterised. X-ray diffraction analysis of complexes reveal a Cu&hellip;Cu distance of 2.9183(13), 2.9604(6), 3.0278(4) and 3.0569(11) &Aring;, respectively. In 1 the metal coordination geometry is intermediate between trigonal bipyramidal (TBP) and square pyramidal (SP) (&tau; = 0.488), in 2 is TBP (0.828 and 0.639) and in 3 and 4 is SP (&tau; = 0.188 and 0.083, respectively). Spectrophotometric investigations to evaluate the catecholase activity of complexes against 3,5-di-tert-butylcatechol (3,5-DTBC) and tetrachlorocatechol (TCC) in three different solvents (acetonitrile, methanol and DMSO) under completely aerobic conditions reveal that complexes 1-4 are able to oxidise 3,5-DTBC in all the solvents, while TCC can be oxidised only in acetonitrile (kcat = 0.0002-0.02 s-1). Intensive DFT calculations prove a ionic pathway for 1-3 while a unique neutral catalytic cycle for 4.

New Journal of Chemistry

Catecholase activity of Mannich-based dinuclear CuII complexes with theoretical modeling: new insight into the solvent role in the catalytic cycle

A novel dinuclear &mu;-diphenoxo-&mu;-acetato metallohydrolase [Ni2L2(NCS)(Ac)(H2O)0.5(MeOH)0.5]&middot;1.25H2O (HL = 2-((E)-(2-(pyridin-2-yl)ethylimino)methyl)-4-chlorophenol) with an intermetallic separation of 3.099 &Aring; has been synthesized and characterized both structurally and spectroscopically. Temperature dependent (2&ndash;300 K) magnetic susceptibility measurements show that the compound exhibits a global intramolecular ferromagnetic interaction through the diphenoxido and&nbsp;syn&ndash;syn&nbsp;acetate bridges (J&nbsp;= 7.21 cm&minus;1). It is also noticed that a weak antiferromagnetic intermolecular interaction or ZFS effect of the Ni(II) ions is working for lowering of &chi;MT&nbsp;at extreme low temperature. The compound&rsquo;s phosphatase activity, investigated spectrophotometrically on 4-nitrophenylphosphate (4-NPP), demonstrates excellent catalytic efficiency. Additionally, using a DMF medium facilitated a better catalytic pathway (8.18 s&minus;1) than when acetonitrile (MeCN) was used. A plausible 4-NPP hydrolytic reaction mechanism was proposed by utilizing DFT calculations and the results suggest a SN2-like addition&ndash;substitution pathway with two possible catalyst&ndash;substrate binding modes (RC1-1 and RC1-2). RC1-2 is regarded as the direct reactant since the water molecule is adjacent to the electron-deficient phosphorus center of the substrate. More importantly, the poor catalytic behavior in the MeCN medium could be ascribed to MeCN molecules having better coordination properties than DMF molecules, since the formation energies of [Ni&ndash;MeCN] and [Ni&ndash;DMF] are &minus;2.5 and &minus;1.2 kcal mol&minus;1, respectively, according to PCM calculations.

<img alt="Graphical abstract: Role of solvent in the phosphatase activity of a dinuclear nickel(ii) complex of a Schiff base ligand: mechanistic interpretation by DFT studies" src="https://pubs.rsc.org/en/Image/Get?imageInfo.ImageType=GA&amp;imageInfo.ImageIdentifier.ManuscriptID=C6NJ01043A&amp;imageInfo.ImageIdentifier.Year=2016" title="Graphical abstract" />

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Role of solvent in the phosphatase activity of a dinuclear nickel(ii) complex of a Schiff base ligand: mechanistic interpretation by DFT studies

Six zinc(II) complexes have been synthesized from two designed Mannich-base ligands which consist of three dinuclear complex [Zn2(L1 )2X2] (1–3) and three mononuclear complex [ZnH(L2 )X2] (4–6), respectively, where X = Cl- (1,4), Br- (2,5), I- (3,6), as reported earlier by us (Sanyal et al., Inorg Chem 53:85–96, 2014). The catecholase activity of the complexes has been investigated under completely aerobic conditions in DMF- water medium (9:1) at pH 8.5 against the model substrate 3,5-di-tert-butylcatechol (3,5-DTBC). Saturation kinetic studies show that the order of conversion of substrate to product (quinone) follows the trend 5[4[2[1 while 3 and 6 are inactive. The generation of phenoxyl radicals, confirmed by UV–vis and EPR spectral studies, is supposed to be responsible for the oxidation of 3,5-DTBC. The in vitro evaluation of 1–6 comprises the study of their DNA-cleaving ability using plasmid DNA and the assess- ment of their cytotoxic activity against Jurkat (T cell lymphoma) cell line by MTT assay. The mechanisms of toxicity appeared to be predominantly by reactive oxygen species (ROS). The comparative analysis helps to arrive at the following facts under experimental conditions: (1) mononuclear species prevail over the dinuclear ones, unlike the behavior in phosphatase activity as reported in Inorganic Chemistry; (2) the halide substituents at the active site control the overall activity in the order: (a) In catecholase activity, Cl-\Br- (dinuclear) and Cl-[Br- (mononuclear) and (b) in biological activity, Cl-[Br-[I - regardless of nuclearity.

JBIC Journal of Biological Inorganic Chemistry

Catecholase activity, DNA cleavage and cytotoxicity of six Zn(II) complexes synthesized from designed Mannich ligands: higher reactivity of mononuclear over dinuclear

A library of 15 dicopper complexes as synthetic analogues of catechol oxidase has been synthesized with the aim to determine the relationship between the electrochemical behavior of the dicopper(II) species in the absence as well as in the presence of 3,5-di-tert-butylcatechol (3,5-DTBC) as model substrate and the catalytic activity, kcat, in DMSO medium. The complexes have been characterized by routine physicochemical techniques as well as by X-ray single-crystal structure analysis in some cases. Fifteen “end-off” compart- mental ligands have been designed as 1 + 2 Schiff-base condensation product of 2,6-diformyl-4-R-phenol (R = Me, t Bu, and Cl) and five different amines, N-(2-aminoethyl)- piperazine, N-(2-aminoethyl)pyrrolidine, N-(2-aminoethyl)- morpholine, N-(3-aminopropyl)morpholine, and N-(2-aminoethyl)piperidine. Interestingly, in case of the combination of 2,6- diformyl-4-methylphenol and N-(2-aminoethyl)morpholine/N-(3-aminopropyl)morpholine/N-(2-aminoethyl)piperidine 1 + 1 condensation becomes the reality and the ligands are denoted as L21−3 . On reaction of copper(II) nitrate with L21−3 in situ complexes 3, 12, and 13 are formed having general formula Cu2(L21−3 )2(NO3)2. The remaining 12 ligands obtained as 1 + 2 condensation products are denoted as L11−12, which produce complexes having general formula Cu2(L11−12)(NO3)2. Catecholase activity of all 15 complexes has been investigated in DMSO medium using 3,5-DTBC as model substrate. Treatment on the basis of Michaelis−Menten model has been applied for kinetic study, and thereby turnover number, kcat, values have been evaluated. Cyclic voltametric (CV) and differential pulse voltametric (DPV) studies of the complexes in the presence as well as in the absence of 3,5-DTBC have been thoroughly investigated in DMSO medium. From those studies it is evident that oxidation of 3,5-DTBC catalyzed by dicopper(II) complexes proceed via two steps: first, semibenzoquinone followed by benzoquinone with concomitant reduction of CuII to CuI . Our study reveals that apparently there is nearly no linear relationship between kcat and E° values of the complexes. However, a detailed density functional theory (DFT) calculation sheds light on this subject. A very good correlation prevails in terms of the energetics associated with the CuII to CuI reduction process and kcat values, as revealed from the combined theoretical and experimental approach.

Inorganic Chemistry

Relation between the Catalytic Efficiency of the Synthetic Analogues of Catechol Oxidase with Their Electrochemical Property in the Free State and Substrate-Bound State

Journal	Data powered by TypesetInorganica Chimica Acta
Publisher	Data powered by TypesetElsevier S.A.
ISSN	0020-1693