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

The origin of catecholase-like activity of Mn(ii)–Schiff-base complexes has been explored by studying structurally characterized mono-, di- and polynuclear Mn(ii) complexes of two "end-off" compartmental Schiff-base ligands

Auxiliary Part of Ligand Mediated Unique Coordination Chemistry of Copper (II)

Six N,N,O-donor Schiff-base ligands, HL1-HL6, [HL1/HL2/HL3= {2-(2-piperazin-1-yl)ethylimino)methyl)-4-(Cl/H/Me)-phenol}; HL4/HL5/HL6={2-(2-morpholine/piperidine/ pyrrolidine 1-yl)ethylimino)methyl)-4-chlorophenol}, have been designed by combining 5-R-2-hydroxy-benzaldehyde, (R=Cl/H/Me) and N-(2-aminoethyl)-Y, (Y=piperazin/morpholine/ piperidine/pyrrolidine) with the view to explore the role of R and X (part of Y excluding coordinating N) on the coordination chemistry of Cu (II) in presence of bromide as counter anion. HL1-HL6 formed in situ on reaction with Cu(II)Br2 produce complexes 1\u20136, respectively. Complex 1, [Cu(II)2Cu(I)2(L1)(MeOH)2Br7.30], is a mixed valence Cu(I)-Cu(II) species having phenyl ring brominated at ortho position with 0.65 occupancy. Complexes 2\u20134 are mononuclear species with general formula [Cu{L2/L3/L4)}Br2]. Complexes [Cu3(L5)Br4] (5) and [Cu3(L6)Br4] (6) are trinuclear species having similar structure but exhibit different magnetic property, 5 is ferro- (J= +16.64 cm1 ) and 6 is antiferromegnetic (J= \u201311.76 cm1). The influence of R and X on bromination, magnetic property and nuclearity issues have been rationalized by DFT calculations

Bioactive Heterometallic CuII–ZnII Complexes with Potential Biomedical Applications

[EN]A series of multinuclear heterometallic Cu-Zn complexes of molecular formula [(CuL)2Zn(dca)2] (1), [(CuL)2Zn(NO3)2] (2), [(CuL)2Zn2(Cl)4] (3), and [(CuL)2Zn2(NO2)4] (4) have been synthesized by reacting [CuL] as a "metalloligand (ML)" (where HL = N,N′-bis(5-chloro-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine) and by varying the anions or coligands using the same molar ratios of the reactants. All of the four products including the ML have been characterized by infrared and UV-vis spectroscopies and elemental and single-crystal X-ray diffraction analyses. By varying the anions, different structures and topologies are obtained which we have tried to rationalize by means of thorough density functional theory calculations. All of the complexes (1-4) have now been applied for several biological investigations to verify their therapeutic worth. First, their cytotoxicity properties were assessed against HeLa human cervical carcinoma along with the determination of IC50 values. The study was extended with extensive DNA and protein binding experiments followed by detailed fluorescence quenching study with suitable reagents to comprehend the mechanistic pathway. From all of these biological studies, it has been found that all of these heterometallic complexes show more than a few fold improvement of their therapeutic values as compared to the similar homometallic ones probably because of the simultaneous synergic effect of copper and zinc. Among all of the four heterometallic complexes, complex 3 exhibits highest binding constants and IC50 values suggest for their better interaction toward the biological targets and hence have better clinical importance

A Deep Insight into the Photoluminescence Properties of Schiff Base Cd(II) and Zn(II) Complexes

A tridentate N,N,O donor ligand 2,4-dichloro-2-[(2-piperazine-4-yl-ethylimino)-methyl]-phenol (HL) was designed, and eight new Zn(II) and Cd(II) complexes, namely, [Zn(LH)(SCN)2] (1), [Zn(LH)(N3)2] (2), [Zn(LH)(NO2)2] (3), [Zn(LH)(dca)(OAc)] (4), [Cd2(LH)2(SCN)4] (5), [Cd(LH)(N3)2] (6), [Cd(LH)(NO2)2] (7), and [Cd(LH)(dca)(OAc)] (8) [where dca = dicyanamide anion] were synthesized. Five of them (1, 2, 4, 5, 7) were structurally characterized through single-crystal X-ray diffraction analysis. H-Bonding interactions are found to be the major stabilizing factor for crystallization in the solid state. Experimental and computational studies were performed in cooperation to provide a rationalization of the photoluminescence properties of those complexes. The quantum yields are anion-dependent, with enhanced efficiencies in the following order: LH < Cd-SCN(5) < Cd-dca(8) < Cd-N3(6) < Cd-NO2(7) < Zn-dca(4) < Zn-N3(2) < ZnNO2(3) < ZnSCN(1). By using quantum chemical calculations we rationalized the above trends. Moreover, the diverse lifetimes observed for those eight complexes were also quantitatively explained by considering the subtle competition between different photo-deactivation pathways

Azido bridge mediated catecholase activity, electrochemistry and magnetic behavior of a dinuclear copper(II) complex of a phenol based "end-off" compartmental ligand

A dinuclear Cu(II) species [Cu2L2(H2O)2(N3)](NO3)2 (L = 2,6-bis(N-ethylpyrrolidine-iminomethyl)-4-methyl-phenolato) where two Cu centers are bridged by phenoxido and l1,1-azido bridges with Cu\u2013Cu separation of 3 \uc5 have been synthesized with the view to explore the role of azido bridge on catecholase activity and electrochemical property and the roles of both the bridging groups on magnetic coupling of two copper centers. The complex exhibits excellent catecholase activity in acetonitrile as well as in DMSO medium not only by oxidizing 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very thorny to oxidize, under aerobic conditions and becomes the first example of its own kind. CV study reveals three quasi-reversible reductive couples which are tentatively assigned as Cu2 II to CuIICuI and CuICuI reduction followed by reduction of CuICuI complex to Cu0Cu0 species. Variable temperature magnetic study suggests the presence of an antiferromagnetic spin\u2013exchange interaction between Cu(II) ions in the dimer via double bridge where the antiferromagnetic contribution of phenoxido bridge predominates over the ferromagnetic interaction of azido bridge

Solvent dependent ligand transformation in a dinuclear copper(ii) complex of a compartmental Mannich-base ligand: Synthesis, characterization, bio-relevant catalytic promiscuity and magnetic study

7siAn “end-off” pentadentate compartmental ligand HL has been synthesized by Mannich base condensation using p-cresol and 2-benzyl amino ethanol and structurally characterized. A dinuclear copper(II) complex, namely [Cu2(L)(m-OH)(H2O)(ClO4)2], has been prepared by treating HL with Cu(ClO4)2$6H2O in methanolic solution with the aim of investigating its catalytic promiscuity. Single crystal structural analysis reveals that the Cu–Cu separation is 2.9 °A. Catecholase activity of the complex has been investigated in anhydrous DMSO as well as in a DMSO–water mixture with progressively increasing the quantity of water up to a 1 : 1 volume ratio in order to assess the bio compatibility of the catalyst using 3,5-DTBC as a model substrate. In anhydrous DMSO the catalytic activity reaches its peak and decreases with increasing water concentration, a feature most likely due to insolubility of 3,5-DTBQ, the product formed in the catalysis, in water. The complex also shows excellent phosphatase-like activity by exploiting the Lewis acidity, the necessary requirement for that activity, under different pH. Thorough investigation reveals that no activity is observed at pH 6 but the activity increases with increasing pH and attains a maximum at pH 9. A variable temperature magnetic study shows that the two Cu centers are antiferromagnetically coupled at low temperature with a J value of 78.63 1.30 cm1. In acetonitrile medium the complex shows very exciting behavior. A new transformed ligand is generated that has been assigned as a Schiff-base ligand, 2,6-bis-[(2-hydroxy-ethylimino)-methyl]-4-methylphenol. The genesis of the new ligand is a consequence of dealkylation from HL followed by oxidation. This oxidation is counterbalanced by reduction of Cu(II) to Cu(I) as is evidenced from isolation of [Cu(MeCN)4](ClO4) from the mixture followed by X-ray structural characterization of the species.reservedmixedMajumder, Ishani; Chakraborty, Prateeti; Das, Sudhanshu; Kara, Hulya; Chattopadhyay, Shymal Kumar; Zangrando, Ennio; Das, DebasisMajumder, Ishani; Chakraborty, Prateeti; Das, Sudhanshu; Kara, Hulya; Chattopadhyay, Shymal Kumar; Zangrando, Ennio; Das, Debasi

Photometric Study of the Interaction of Zinc (II) Complexes of Schiff Bases with Cetyltrimethyl Ammonium Bromide

A detailed photophysical behavioral study of zinc (II) complexes of Schiff bases 2,6-bis((E)-((2-(dimethylamino) ethyl)imino)methyl)-4-R-phenol, where R = methyl (1)/isopropyl (2)/tertiary butyl (3)/chloro (4) for ligands 1 to 4 (HL1 to HL4) have been done by utilising the surfactant cetyltrimethyl ammonium bromide as the biomimicking environment. Steady state absorption and emission studies have been studied to investigate the course of deciphering of the photophysical behavior of the complexes. The study reveals modification of the photophysical properties of the complexes based on the effect of polarity of the micellar environment. The studies reported in the present investigation describe the initial reduction of fluorescent intensity of all the four complexes followed by an escalation in intensity. The binding constant values reveal that the Schiff bases bind to the micellar compartment. The course of binding is however found to be dependent on the functional group of the ligand which is studied and reported in the present context.</p

Influence of para substituents in controlling photophysical behavior and different non-covalent weak interactions in zinc complexes of a phenol based "end-off" compartmental ligand

Three dinuclear zinc(II) complexes with "end-off" compartmental ligands, namely 2,6-bis(N-ethylmorpholine-iminomethyl)-4-R-phenol (I: R = -CH3, Cl, tBu) were synthesized with the aim of exploring the role of the para substituent present in the ligand backbone in controlling the structural diversity, photophys. properties and different weak interactions of the complexes. The complexes are [Zn2L1(CH3CO2)2]1/2[Zn(NCS)4].3/2H2O (1), [Zn2L2(CH3CO2)2]1/2[Zn(NCS)4] (2), and [Zn2L3(CH3CO2)2]1/2[Zn(NCS)4] (3),. All three species, with the general formula 2[Zn2L(CH3COO)2][Zn(NCS)4], show the complex anion Zn(NCS)42- as a common structural feature decisive for crystn. All of them possess several noncovalent weak interactions where the nature of the "R'' group plays an essential role as exposed by DFT study. Besides exhibiting fluorescence behavior, the complexes also show para substitution controlled phosphorescence both at room and low temp. Anisotropy studies suggest the existence of complexes 2 and 3 as dimers in soln. The origins of the unusual room temp. phosphorescence and fluorescence behavior of the complexes were rationalized in the light of theor. calcns. [on SciFinder(R)

A Deep Insight into the Photoluminescence Properties of Schiff Base Cd^II and Zn^II Complexes

A tridentate N,N,O donor ligand 2,4-dichloro-2-[(2-piperazine-4-yl-ethylimino)-methyl]-phenol (HL) was designed, and eight new Zn^II and Cd^II complexes, namely, [Zn­(LH)­(SCN)₂] (<b>1</b>), [Zn­(LH)­(N₃)₂] (<b>2</b>), [Zn­(LH)­(NO₂)₂] (<b>3</b>), [Zn­(LH)­(dca)­(OAc)] (<b>4</b>), [Cd₂(LH)₂­(SCN)₄] (<b>5</b>), [Cd­(LH)­(N₃)₂] (<b>6</b>), [Cd­(LH)­(NO₂)₂] (<b>7</b>), and [Cd­(LH)­(dca)­(OAc)] (<b>8</b>) [where dca = dicyanamide anion] were synthesized. Five of them (<b>1</b>, <b>2</b>, <b>4</b>, <b>5</b>, <b>7</b>) were structurally characterized through single-crystal X-ray diffraction analysis. H-Bonding interactions are found to be the major stabilizing factor for crystallization in the solid state. Experimental and computational studies were performed in cooperation to provide a rationalization of the photoluminescence properties of those complexes. The quantum yields are anion-dependent, with enhanced efficiencies in the following order: LH < Cd-SCN­(<b>5</b>) < Cd-dca­(<b>8</b>) < Cd–N₃(<b>6</b>) < Cd-NO₂(<b>7</b>) < Zn-dca­(<b>4</b>) < Zn–N₃(<b>2</b>) < ZnNO₂(<b>3</b>) < ZnSCN­(<b>1</b>). By using quantum chemical calculations we rationalized the above trends. Moreover, the diverse lifetimes observed for those eight complexes were also quantitatively explained by considering the subtle competition between different photo-deactivation pathways

Probing the binding interaction of zinc (II) Schiff bases with bovine serum albumin: A spectroscopic and molecular docking study

Entrapping of potent Schiff base with biomimetic environment using fluorescence properties enables better understanding of their interaction for drug-based application. A detailed photophysical study of zinc (II) Schiff bases, 2,6-bis((E)-((2-(dimethylamino) ethyl)imino)methyl)-4-R-phenol, where R = methyl/tertiary butyl/chloro is reported by utilizing bovine serum albumin (BSA) as the bio membrane. Steady state absorption and emission studies of Schiff base-protein system have been found to get altered by change in the compartmental ligand. Alternation of polarity caused by such compartmental ligands is reported by comparing the fluorescence behavior of the probes in microheterogeneous environment in a mixture of dioxane and water of varying composition. Hildebrand equation accounts for negative binding constants among BSA with Schiff base with Cl (-I) group as the compartmental ligand in contrast to the positive magnitudes with ligands exhibiting +I effect. Functionality of such compartmental ligands (intra interactions studied using Hirshfeld analyses) upon binding with the protein is also studied in terms of quenching and denaturation studies. Schiff base with Me is found to be the most favorable ligand that bound to BSA as corroborated from the binding, quenching, micropolarity, and docking studies. Molecular docking studies predict the affinity energies for suitable binding conformations to be similar to - 6 kcal mol(-1) for BSA-Schiff base (with Me ligand)