Tridentate Donor Research Articles

New Cu(II), Co(III) and Ni(II) metal complexes based on ONO donor tridentate hydrazone: Synthesis, structural characterization, and investigation of some biological properties

New Cu(II), Co(III) and Ni(II) metal complexes of N'-(3-ethoxy-2-hydroxybenzylidene)acetohydrazide (ehbahH2) ligand derived from 3-ethoxysalicylaldehyde and acethydrazide were obtained. The K[Cu(ehbah)(OAc)]·2H2O (1), K[Co(ehbah)2]·H2O (2) and [Ni(ehbahH)2] (3) complexes were characterized by elemental analysis, LC-MS and magnetic susceptibility measurements, electronic, IR spectra and thermal experiments (TGA and DTA). The molecular structures of 1 and 2 were also established by single-crystal X-ray diffraction. Both complexes had a complex ion unit and a potassium (I) cation leading to a neutral three-dimensional network. The single-crystal X-ray experiments revealed that the complex ions of 1 and 2 exhibited distortion in the square-planar and octahedral geometry, with ligand in enol form. The characterization studies of the complex 3 showed that the ligand was coordinated in the keto tautomeric form, and the ratio of metal ligand was 1:2. All of the compounds were screened for their in vitro antibacterial and antifungal activity. The cleavage activities of the ligand and its complexes were assayed on supercoiled pBR322 DNA by the agarose gel electrophoresis method in the presence and absence of H2O2. The results indicated that only 1 and 2 effectively cleaved pBR322 DNA. Lastly, all compounds obtained in the study were evaluated for their antioxidant (ABTS radical scavenging) properties.

Synthesis, Characterisation, Crystal Structure and Anti-corrosion Studies of an Organotin(IV) Complex of 2-acetylpyridine 4-ethyl-3-thiosemicarbazone (LH): n-BuSn(L)Cl2

This study explored the possibility of Schiff-base ligand compound, 2-acetylpyridine 4-ethyl-3-thiosemicarbazone (LH) and its organotin(IV) complex (BuSn(L)Cl2) as a corrosion inhibitor for mild steel in 1M hydrochloric acid (HCl) medium. The chemical structures of the synthesised compounds were confirmed by performing elemental analysis, FT-IR, UV-Vis, NMR spectroscopy, and X-ray crystallography diffraction study. The structure showed the LH served as a tridentate (N, N’, S) donor to tin through its pyridyl, azomethine nitrogen, and thiolate sulphur. The corrosion inhibition characteristics of the free Schiff-base ligand and its organotin complex were studied by the standard weight loss method. They showed inhibition activity through adsorption, and this phenomenon was found to obey Langmuir adsorption isotherm. The inhibition efficiency of both compounds was found to increase as their concentration was increased from 1 to 3mM, but the efficiency achieved with the tin complex was greater, being 98.98% at 3mM concentration.

Biologically active novel N, N, O donor tridentate water soluble hydrazide based O-carboxymethyl chitosan Schiff base Cu (II) metal complexes: Synthesis and characterisation

Water soluble hydrazide based O-carboxymethyl chitosan Schiff base ligands have been prepared from chitosan and a mixture of benzoic acidhydrazide with β-diketone by carboxymethylation using mono chloroaceticacid (MCA) through in-situ reaction. The degree of deacetylation of chitosan was determined by elemental analysis and potentiometric titration. Schiff base ligands and the functional groups were characterised by FT-IR, 1H, and 13C NMR spectroscopic techniques. The crystallinity of ligands and complexes was evaluated by X-ray powder diffraction (XRD) studies. Thermal stability of all the synthesized compounds was investigated by thermo gravimetric analysis and differential thermal analysis (TGA-DTA) which revealed the presence of metal oxide (CuO) residue to elevate the temperature to >500 °C. Filed emission scanning electron microscopic (FESEM) analysis revealed that Cu (II) complexes were more amorphous in nature than chitosan and Schiff base ligands. Vibrating sample magnetometer (VSM) studies reported that the d9 configuration of the metal complex was paramagnetic in nature and the geometry of the complex was square pyramidal. The antimicrobial activity of the synthesized hydrazide Cu (II) complexes was characterised by agar plate method, anti-inflammatory study was characterised by egg albumin denaturation technique and total antioxidant activity was characterised by phosphomolybdenum method.

Zinc(ii) centered biologically active novel N,N,O donor tridentate water-soluble hydrazide-based O-carboxymethyl chitosan Schiff base metal complexes: synthesis and characterisation

In this study, novel eco-friendly and water-soluble chitosan Schiff base derivatives have been designed for potential use in antimicrobial applications.

Synthesis & crystal structures of four new biochemical active Ni(II) complexes of thiosemicarbazone and isothiosemicarbazone-based ligands: In vitro antimicrobial study

Four new stable nickel(II) complexes (1–4) with isothiosemicarbazone- and thiosemicarbazone-based ligands, namely, salicylidine S-propyl-isothiosemicarbazone hydroiodide (H2L1.HI), 5-bromo-2-hydroxybenzaldehyde S-propyl-isothiosemicarbazone hydroiodide (H2L2.HI), salicylidine-thiosemicarbazone (H2L3), and 5-bromo-2-hydroxybenzaldehyde thiosemicarbazone (H2L4) accompanied with triphenylphosphine and 2-methylimidazole as ancillary ligands were prepared in good yields. The complexes were characterized using analytical and spectroscopic techniques. Single-crystal X-ray crystallography revealed that the nickel complexes had distorted square planar geometries. H2L1.HI and H2L2.HI acted as NNO, while H2L3 and H2L4 acted as SNO tridentate donor ligands. In vitro antifungal and antibacterial activities of the Ni(II) complexes revealed that 3 exhibited the highest antifungal property especially against Candida albicans with an inhibition zone of 40 mm and a minimum inhibitory concentration, MIC = 1.56 mg/ml). Complex 2 showed the highest antibacterial property especially against Staphylococcus aureus with an inhibition zone of 30 mm and MIC of 1.56 mg/ml. Results indicate that these complexes are potential antimicrobial drugs for the treatment of infectious diseases for further research.

Ni(II) Dimers of NNO Donor Tridentate Reduced Schiff Base Ligands as Alkali Metal Ion Capturing Agents: Syntheses, Crystal Structures and Magnetic Properties

Three trinuclear Ni(II)-Na(I) complexes,[Ni2(L1)2NaCl3(H2O)]·H2O (1), [Ni2(L2)2NaCl3(H2O)] (2), and [Ni2(L3)2NaCl3(OC4H10)] (3) have been synthesized using three different NNO donor tridentate reduced Schiff base ligands, HL1= 2-[(3-methylamino-propylamino)-methyl]-phenol, HL2= 2-[(3-methylamino-propylamino)-methyl]-4-chloro-phenol, and HL3= 2-[(3-methylamino-propylamino)-methyl]-6-methoxy-phenol that had been structurally characterized. Among these complexes, 1 and 2 are isostructural in which dinuclearNi(II) units act as metalloligands to bind Na(I) ions via phenoxido and chlorido bridges. The Na(I) atom is five-coordinated, and the Ni(II) atom possesses hexacordinated distorted octahedral geometry. In contrast, in complex 3, two -OMe groups from the dinuclear Ni(II) unit also coordinate to Na(I) to make its geometry heptacordinated pentagonal bipyramidal. The magnetic measurements of complexes 1–3 indicate ferromagnetic interactions between dimeric Ni(II) units with J = 3.97 cm−1, 4.66 cm−1, and 5.50 cm−1for 1–3, respectively, as is expected from their low phenoxido bridging angles (89.32°, 89.39°, and 87.32° for 1–3, respectively). The J values have been calculated by broken symmetry DFT method and found to be in good agreement with the experimental values.

Synthesis, characterization, DFT and antimicrobial studies of transition metal ion complexes of a new schiff base ligand, 5-methylpyrazole-3yl-N-(2́-hydroxyphenylamine)methyleneimine, (MPzOAP)

A new pyrazole based ‘NNO’ tridentate ligand, 5-methylpyrazole-3yl-N-(2́-hydroxyphenylamine)methyleneimine, (MPzOAP) was synthesized and characterized by elemental analyses, mass, IR, 1H NMR spectral parameters. The versatile coordination mode of the ligand was established by the synthesis of Co(III), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) metal ion complexes. These complexes were characterized by elemental analyses, conductance and magnetic susceptibility measurements, UV–Vis, IR, 1H NMR spectroscopy, PXRD and thermal analysis. The structures of the ligand and complexes were also investigated using the DFT method. The ligand structure contains the coordination function of the tertiary nitrogen atom of pyrazole ring, the azomethine nitrogen and the phenolic oxygen atom, suitably spaced for chelation with a metal ion and acting as a ‘NNO’ tridentate donor ligand. In vitro antimicrobial activity of the reported ligand and the metal ion complexes were screened and the mode of action was also studied by scanning electron microscopy (SEM) against some pathogenic bacteria.

Tetraruthenium Metallamacrocycles with Potentially Coordinating Appended Functionalities

We present four new tetraruthenium macrocycles built from two 1,4-divinylphenylene diruthenium and two isophthalic acid building blocks with peripheral, potentially mono- or tridentate donor functions attached to the isophthalic linkers. These macrocycles are characterized by multinuclear NMR spectroscopy, mass spectrometry and, in the case of the thioacetyl-appended complex 4, by X-ray crystallography. Cyclic and square wave voltammetry establish that the macrocycles can be oxidized in four consecutive redox steps that come as two pairs of two closely spaced one-electron waves. Spectroscopic changes observed during IR and UV/Vis/NIR spectroelectrochemical experiments (NIR = near infrared) show that the isophthalate linkers insulate the electroactive divinylphenylene diruthenium moieties against each other. The macrocycles exhibit nevertheless pronounced polyelectrochromism with highly intense absorptions in the Vis (2+/4+ states) and the NIR (2+ states) with extinction coefficients of up to >100,000 M−1·cm−1. The strong absorptivity enhancement with respect to the individual divinylphenylene diruthenium building blocks is attributed to conformational restrictions imposed by the macrocycle backbone. Moreover, the di- and tetracations of these macrocycles are paramagnetic as revealed by EPR spectroscopy.

Disulfide-masked iron prochelators: Effects on cell death, proliferation, and hemoglobin production

The iron metabolism of malignant cells, which is altered to ensure higher acquisition and utilization, motivates the investigation of iron chelation strategies in cancer treatment. In a prochelation approach aimed at increasing intracellular specificity, disulfide reduction/activation switches are incorporated on iron-binding scaffolds resulting in intracellularly activated scavengers. Herein, this strategy is applied to several tridentate donor sets including thiosemicarbazones, aroylhydrazones and semicarbazones. The novel prochelator systems are antiproliferative in breast adenocarcinoma cell lines (MCF-7 and metastatic MDA-MB-231) and do not result in the intracellular generation of oxidative stress. Consistent with iron deprivation, the tested prochelators lead to cell-cycle arrest at the G1/S interface and induction of apoptosis. Notably, although hemoglobin-synthesizing blood cells have the highest iron need in the human body, no significant impact on hemoglobin production was observed in the MEL (murine erythroleukemia) model of differentiating erythroid cells. This study provides new information on the intracellular effects of disulfide-based prochelators and indicates aroylhydrazone (AH1-S)2 as a promising prototype of a new class of antiproliferative prochelator systems.

Structural resemblance and variation in transition metal complexes derived from dipicolinic acid and guanylhydrazine

New aminoguanidinium transition metal dipicolinates of the formula (AgunH)[MIII(dip)2]·xH2O, M = Cr, x = 1.5; Fe, x = 2, (AgunH)2[MII(dip)2]·nH2O, where M = Mn, n = 2; Co or Ni, n = 0 and Zn, n = 1, and [Cu(Agun)2][Cu3(dip)4(Agun)2]·4H2O have been prepared by the reaction of respective metal nitrates with aqueous mixture of dipicolinic acid (H2dip) and aminoguanidine bicarbonate (AgunH·HCO3) in appropriate mole ratios. These compounds have been characterized by various physico-chemical techniques. Among them Ni, Cu, Cr and Fe complexes have been structurally characterized. The asymmetric units of the Ni and Cr structures contain two independent molecules, whereas Fe has four. Unlike these, the copper compound has a unique structure with a tri-nuclear centrosymmetric anionic complex and cationic bis(aminoguanidine)copper(II). In all of these compounds, the dipicolinate dianion is acting as a tridentate (O,N,O) donor ligand, except copper in-which one of the dipicolinates is tetradentate (O,N,O,O). Cytotoxicity and DPPH scavenging activity studies reveal that the copper complex exhibits superior activity to that of cobalt and nickel.

Ambidentate Ligand Reactivity with the Rhenium(I) Compounds [BrRe(CO)4]2 and cis‐BrRe(CO)4L: A Kinetic and Mechanistic Study

The reaction of the halo‐bridged dimer [BrRe(CO)4]2 with the ambidentate donor 2‐(diphenylphosphanyl)pyridine (PN) has been investigated. The substitution reaction is rapid at room temperature and regioselective for phosphorus coordination to yield exclusively cis‐BrRe(CO)4(κP‐PN) (1). Thermolysis of 1 furnishes the PN‐chelated product fac‐BrRe(CO)3(κP,N‐PN) (2) and CO. The kinetics for the conversion of 1 → 2 + CO have been measured by UV/Vis spectroscopy in toluene over the temperature range of 323–343 K. On the basis of the activation parameters [ΔH‡ = 28.0(0.9) kcal/mol and ΔS‡ = 31(3) eu], a dissociative process is supported, and this was corroborated by electronic structure calculations. The regioselectivity in the ligand‐substitution reaction involving [BrRe(CO)4]2 and the tridentate donor 6‐(diphenylphosphanyl)‐2‐formylpyridine (PON) was also studied, and consistent with the PN donor, only the κP‐product, cis‐BrRe(CO)4(κP‐PON) (3) is formed. The reaction of the dimer [BrRe(CO)4]2 with 2‐(diphenylphosphanyl)pyridine (PN) has been computationally modeled by DFT calculations. The energetics for the creation of an unsaturated intermediate through the cleavage of one of the bridging bromide ligands, followed by the addition of the donor to the unsaturated rhenium center versus the direct attack of the pnictogen donor on the dimer have been evaluated. The latter process is computed as the preferred route for dimer activation, with an attack of the pyridyl moiety slightly favored compared to the phosphine moiety. The computed pnictogen preference agrees with the kinetic data published by Zingales and coworkers. Concerning the reaction of the PN ligand with [BrRe(CO)4]2, we predict the initial formation of the κN‐isomer of 1 as the kinetic product of substitution, which in turn undergoes a rapid isomerization to furnish the thermodynamically more stable κP‐isomer through a reversible ligand dissociation process. The intramolecular linkage isomerization of κN‐1 to κP‐1 in 1 was also investigated by DFT, and the concerted process was found to lie 6.5 kcal/mol above the two‐step process involving ligand dissociation.

Interactions Between Thiocyanate-Free Bis-Tridentate Ru Complexes and Iodide in Dye-Sensitized Solar Cells

Abstract The intermolecular interactions of thiocyanate-free Ru terpyridyl complexes containing a 2,6-disubstituted pyridine as a tridentate donor ligand (BTP, FT19, and TUS-29 dyes) with iodide ions are investigated using density functional theory. Similar to N749 dye with three thiocyanate ligands, the oxidized thiocyanate-free complexes mainly interact with I − and I 2 − ions via the donor ligands. Oxidized BTP with a pyridine-2,6-ditetrazolyl ligand can be regenerated by three different mechanisms: (A) by one I − through a one-step mechanism, (B) by two I − ions via a two-step mechanism, or (C) by I 2 − via a one-step mechanism. Oxidized FT19 with a pyridine-2,6-dicarboxylate ligand can be regenerated via mechanism B or C. Although oxidized TUS-29 with a pyridine-2,6-dicarboxyamidato ligand can be reduced through mechanism C, the regeneration reaction is rather incomplete. The much lower dye-sensitized solar cell performance using TUS-29 dye than N749 is attributed to its inferior regeneration ability.

Steric and electronic factor comparisons in hydrotris(3-phenylpyrazolyl)borate nickel(II) aryloxides

Hydrotris(pyrazolyl)borate (Tp) ligands, also known as scorpionates, are potent tridentate donors that effectively bind metal ions in a face-capping array. Hydrotris(3-phenylpyrazolyl)borate enforces a tetrahedral environment on NiII to model metalloenzymes. The syntheses and structural characterizations of a number of [hydrotris(3-phenylpyrazolyl)borato]nickel(II) aryloxides were performed to provide insight into the environment of the model active site; these compounds are chlorido[hydrotris(3-phenylpyrazolyl-κN2)borato](3-phenyl-1H-pyrazole-κN2)nickel(II) chloroform monosolvate, [Ni(C27H22BN6)Cl(C9H8N2)]·CHCl3, (2), [hydrotris(3-phenylpyrazolyl-κN2)borato](phenolato-κO)nickel(II), [Ni(C27H22BN6)(C6H5O)], (3), (2,6-dimethylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN2)borato]nickel(II) [Ni(C27H22BN6)(C8H9O)], (4), (4-tert-butylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN2)borato]nickel(II), [Ni(C27H22BN6)(C10H13O)], (5), and [hydrotris(3-phenylpyrazolyl-κN2)borato](phenolato-κO)(tetrahydrofuran-κO)nickel(II) tetrahydrofuran monosolvate, [Ni(C27H22BN6)(C6H5O)(C4H8O)]·C4H8O, (6). Alkyl groups, e.g. tert-butyl in (5) and methyl in (4), electronically activate the aryloxide group to intramolecular π-π stacking but can be frustrated by steric encumbrance at the interacting ring faces. The flexibility at the nickel coordination site, afforded by the uncrowded B atom of the TpPh ligand, allows tetrahydrofuran coordination in the phenolate compound.

Synthesis, spectroscopic characterization and antimicrobial studies of oxomolybdenum(V) and dioxomolybdenum(VI) complexes with NNS donor tridentate Schiff base ligands

Synthesis, spectroscopic characterization and antimicrobial studies of oxomolybdenum(V) and dioxomolybdenum(VI) complexes with NNS donor tridentate Schiff base ligands

Synthesis, characterization and self-assembly of three dicyanamide bridged polynuclear copper(II) complexes with N2O donor tridentate Schiff bases as blocking ligands

Three copper(II) complexes [Cu(L1)(μ1,5-dca)]n (1), [Cu(L2)(μ1,5-dca)]n (2) and [Cu(L3)(μ1,5-dca)]n (3) [where HL1=(1-(2-(dimethylamino)ethylimino)ethyl) naphthalene-1-ol, HL2=(1-(2-(methylamino)ethylimino)ethyl) naphthalene-1-ol and HL3=(1-(2-(ethylamino)ethylimino)ethyl)naphthalene-1-ol] have been synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy. The structure of each complex has been confirmed by single-crystal X-ray diffraction studies. In all three complexes, copper(II) centres are bridged by dicyanamide in end to end fashion. Complexes 1 and 2 are zigzag polymers, whereas complex 3 is a helical one. The weak forces like C–H⋯π and π⋯π interactions influence the self-assembly process in all three complexes. Such types of interactions lead to the formation of interesting supra molecular networks in three complexes.

Construction of Hetero‐Four‐Layered Tripalladium(II) Cyclophanes by Transannular π⋅⋅⋅π Interactions

AbstractA synthetic strategy for the generation of new molecular species utilizing a provision of nature is presented. Nano‐dimensional (23(2)×21(1)×16(1) Å3) hetero‐four‐layered trimetallacyclophanes were constructed by proof‐of‐concept experiments that utilize a suitable combination of π⋅⋅⋅π interactions between the central aromatic rings, tailor‐made short/long spacer tridentate donors, and the combined helicity. The behavior of the unprecedented four‐layered metallacyclophane system offers a landmark in the development of new molecular systems.

Construction of Hetero-Four-Layered Tripalladium(II) Cyclophanes by Transannular π⋅⋅⋅π Interactions.

A synthetic strategy for the generation of new molecular species utilizing a provision of nature is presented. Nano-dimensional (23(2)×21(1)×16(1) ų) hetero-four-layered trimetallacyclophanes were constructed by proof-of-concept experiments that utilize a suitable combination of π⋅⋅⋅π interactions between the central aromatic rings, tailor-made short/long spacer tridentate donors, and the combined helicity. The behavior of the unprecedented four-layered metallacyclophane system offers a landmark in the development of new molecular systems.

Synthetic and Structural Studies of Mixed Sodium Bis(trimethylsilyl)amide/Sodium Halide Aggregates in the Presence of η(2)-N,N-, η(3)-N,N,N/N,O,N-, and η(4)-N,N,N,N-Donor Ligands.

When n-hexane solutions of an excess of sodium bis(trimethylsilyl)amide (NaHMDS) are combined with cesium halide (halide = Cl, Br, or I) in the presence of the tetradentate donor molecule [tris[2-(dimethylamino)ethyl]amine] (Me6TREN), the isolation and characterization of a series of sodium amide/sodium halide mixed aggregates was forthcoming. Cesium halide was employed because it efficiently reacted with NaHMDS to produce a molecular, soluble source of sodium halide salt (which was subsequently captured by an excess of NaHMDS) via a methathetical reaction. These mixed sodium amide/sodium halide complexes are formally sodium sodiates, are deficient in halide with respect to the amide, and have the general formula [{Na5(μ-HMDS)5(μ5-X)}{Na(Me6TREN)}] [where X = Cl (1), Br (2), or I (3)]. The influence of the donor ligand was studied for the NaI/NaHMDS system, and when n-hexane solutions of this composition were treated with tridentate donors such as N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDETA) or N,N,N',N'-tetramethyldiaminoethyl ether (TMDAE), solvent-separated ion-pair cocomplexes [Na5(μ-HMDS)5(μ5-I)](-)[Na3(μ-HMDS)2(PMDETA)2](+) (4) and [Na5(μ-HMDS)5(μ5-I)](-)[Na(TMDAE)2](+) (5) were isolated. However, upon reaction with bidentate proligands such as the chiral diamine (R,R)-N,N,N',N'-tetramethylcyclohexane-1,2-diamine [(R,R)-TMCDA] or N,N,N',N'-tetramethylethylenediamine (TMEDA), neutral complexes [Na4(μ-HMDS)3(μ4-I)(donor)2] [donor = (R,R)-TMCDA (6) and TMEDA (7)] were produced. To illustrate the generality of the latter reaction with other halides, [Na4(μ-HMDS)3(μ4-Br)(TMEDA)2] (8) was also prepared by employing NaBr in the synthesis instead of NaI.

Developing lithium chemistry of 1,2-dihydropyridines: from kinetic intermediates to isolable characterized compounds.

Generally considered kinetic intermediates in addition reactions of alkyllithiums to pyridine, 1-lithio-2-alkyl-1,2-dihydropyridines have been rarely isolated or characterized. This study develops their "isolated" chemistry. By a unique stoichiometric (that is, 1:1, alkyllithium/pyridine ratios) synthetic approach using tridentate donors we show it is possible to stabilize and hence crystallize monomeric complexes where alkyl is tert-butyl. Theoretical calculations probing the donor-free parent tert-butyl species reveal 12 energetically similar stereoisomers in two distinct cyclotrimeric (LiN)3 conformations. NMR spectroscopy studies (including DOSY spectra) and thermal volatility analysis compare new sec-butyl and iso-butyl isomers showing the former is a hexane soluble efficient hydrolithiation agent converting benzophenone to lithium diphenylmethoxide. Emphasizing the criticalness of stoichiometry, reaction of nBuLi/Me6 TREN with two equivalents of pyridine results in non-alkylated 1-lithio-1,4-dihydropyridine⋅Me6 TREN and 2-n-butylpyridine, implying mechanistically the kinetic 1,2-n-butyl intermediate hydrolithiates the second pyridine.

A polymer grafted oxidomethoxidovanadium(V) complex of an ONO donor ligand mimicking peroxidase activity

The reaction between [VIVO(acac)2] and the ONO donor tridentate ligand H2hap-iah (I) [H2hap-iah=Schiff base obtained by the condensation of equimolar amounts of o-hydroxyacetophenone (hap) and indole-3-acetic hydrazide (iah)] in an equimolar ratio under an oxygen atmosphere in refluxing methanol gives [VVO(OMe)(hap-iah)] (1). Treatment of 1 in methanol with H2O2 in the presence of KOH results in the formation of K[VVO(O2)(hap-iah)] (2). Complex 1 has been grafted into chloromethylated polystyrene cross-linked with 5% divinylbenzene {now abbreviated as PS-[VVO(OMe)(hap-iah)] (3)} via covalent bonding through the imino nitrogen atom of the indole group. The two complexes have been characterized by various spectroscopic techniques (IR, electronic, 1H, 13C and 51V NMR, ESI-MS), analytical and thermal studies. The polymer-grafted complex 3 has also been analyzed by field-emission scanning electron micrographs (FE-SEM) as well as energy dispersive X-ray (EDAX) studies. The polymer-grafted complex 3 has been used as a catalyst for the peroxidase-like oxidation of pyrogallol to purpurogallin in pH 7 buffer solution. Its high peroxidase mimicking ability, easy separation from the reaction medium and the reusability, without any considerable decrease in activity, suggest the practical utility of the catalyst.