Ligand assembly and metal ion complexation: syntheses and X-ray structures of Ni(II) and Cu(II) benzoate and 4-tert-butylbenzoate complexes of cyclam

The syntheses and X-ray structures of trans-[Ni(O-benzoato)₂(cyclam)], trans-[Cu(H₂O)₂(cyclam)]-(benzoate)₂·2H₂O and trans-[Cu(H₂O)₂(cyclam)](4-t-butyl-benzoate)₂ (where cyclam is 1,4,8,11-tetraazacyclotetradecane) are described. The nickel complex has a tetragonally distorted octahedral coordination geometry with cyclam occupying the equatorial plane in a stable trans-III arrangement, with benzoate ligands filling the axial positions. The structure closely resembles the arrangement in the previously described hydrogen-bonded (metal-free) ligand assembly [(cyclamH₂)·(4-t-butyl benzoate)₂]·2(benzoic acid) if the latter benzoic acid moieties, which do not interact directly with the cyclam moiety, are ignored. The 2?:?1 fragment thus may be viewed as a ligand assembly “preorganized” for nickel ion complexation. In contrast to the nickel structure, the two trans-axial sites in both copper structures are occupied by aqua rather than O-carboxylate ligands. Although they do not form part of the inner coordination sphere in either complex, the two carboxylate anions remain hydrogen bound to the (coordinated) cyclam ligand, with the mode of packing being generally similar in each complex.     

Thermal, spectral and magnetic characterization of Co(II), Ni(II) AND Cu(II) 4-chloro-2-nitrobenzoates

Physico-chemical properties of 4-chloro-2-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono- and trihydrates with a metal ion to ligand ratio of 1:2. All analysed 4-chloro-2-nitrobenzoates are polycrystalline compounds with colours depending on the central ions: pink for Co(II), green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293–523 K, because it was found that on heating in air above 523 K 4-chloro-2-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step and anhydrous compounds are formed. The final products of their decomposition are the oxides of the respective transition metals. From the results it appears that during dehydration process no transformation of nitro group to nitrite takes place. The solubilities of analysed complexes in water at 293 K are of the order of 10^–4–10^–2 mol dm^–3. The magnetic moment values of Co²⁺, Ni²⁺ and Cu²⁺ ions in 4-chloro-2-nitrobenzoates experimentally determined at 76–303 K change from 3.89 to 4.82 μ_B for Co(II) complex, from 2.25 to 2.98 μ_B for Ni(II) 4-chloro-2-nitrobenzoate, and from 0.27 to 1.44 μ_B for Cu(II) complex. 4-chloro-2-nitrobenzoates of Co(II), and Ni(II) follow the Curie–Weiss law. Complex of Cu(II) forms dimer.     

Thermal, spectral and magnetic behaviour of 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II) AND Cu(II)

Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505–517 K. Next in the range of 505–1205 K they decompose to the following oxides: Mn₃O₄, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390–443 K it loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of 10^–3 mol dm^–3 for the Mn(II) complex and 10^–4 mol dm^–3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77–300 K change from 5.64–6.57 μB (for Mn²⁺), 4.73–5.17 μB (for Co²⁺), 3.26–3.35 μB (for Ni²⁺) and 0.27–1.42 μB (for Cu²⁺). 2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss law, whereas that of Cu(II) forms a dimer.     

The Structure of Nickel(Ii) and Copper(Ii) Complexes with 1,4,8,11-Tetraazacyclotetradecanein Aqueous Solution as Studied by the X-Ray Diffraction Method

The structure of 1,4,8,11-tetraazacyclotetradecane (cyclam) complexes with nickel(II) and copper(II) ions in aqueous solution has been determined by the x-ray diffraction method at 25°C. The [Ni-(cyclam)]²⁺ complex has a square-planar structure with four nitrogen atoms of the cyclam, and the Ni-N bond length has been determined to be 198 pm. Upon the addition of ammonia, the color of the nickel(II)-cyclam solution turns to deep purple and the [Ni(NH₃)₂(cyclam)]²⁺ complex is formed. The complex has a regular octahedral structure with an additional two NH₃ molecules along the axis vertical of the cyclam plane, and the Ni-N (NH₃ and cyclam) bond lengths are 209 pm. The copper(II)-cyclam complex in the aqueous solution is a distorted octahedron with two water molecules along the elongated axis. The axial Cu—O and equatorial Cu—N bond lengths are 277 and 210 pm, respectively.     

Complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 4-chloro-2-methoxybenzoic acid anion

The complexes of 4-chloro-2-methoxybenzoic acid anion with Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ were obtained as polycrystalline solids with general formula M(C₈H₆ClO₃)₂·nH₂O and colours typical for M(II) ions (Mn – slightly pink, Co – pink, Ni – slightly green, Cu – turquoise and Zn – white). The results of elemental, thermal and spectral analyses suggest that compounds of Mn(II), Cu(II) and Zn(II) are tetrahydrates whereas those of Co(II) and Ni(II) are pentahydrates. The carboxylate groups in these complexes are monodentate. The hydrates of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) heated in air to 1273 K are dehydrated in one step in the range of 323–411 K and form anhydrous salts which next in the range of 433–1212 K are decomposed to the following oxides: Mn₃O₄, CoO, NiO and ZnO. The final products of decomposition of Cu(II) complex are CuO and Cu. The solubility value in water at 293 K for all complexes is in the order of 10^–3 mol dm^–3. The plots of χ_M vs. temperature of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) follow the Curie–Weiss law. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in these complexes were determined in the range of 76−303 K and they change from: 5.88–6.04 μ_B for Mn(C₈H₆ClO₃)₂·4H₂O, 3.96–4.75 μ_B for Co(C₈H₆ClO₃)₂·5H₂O, 2.32–3.02 μ_B for Ni(C₈H₆ClO₃)₂·5H₂O and 1.77–1.94 μ_B for Cu(C₈H₆ClO₃)₂·4H₂O.     

Synthesis,crystal structure and magnetic properties of a new binuclear copper(II)-copper(II) complex of a macrocyclic oxamide

The binuclear metal complex [Cu(μ-exoO₂)cyclamCu(bpy)](ClO₄)₂·H₂O (bpy?=?2,2′-bipyridine and (exoO₂)cyclam?=?1,4,8,11-tetraazacyclotradecanne-2,3-dione) has been synthesized and characterized by single-crystal X-ray analysis and spectroscopic and magnetic measurements. The structure consists of homobinuclear [Cu(μ-exoO₂)cyclamCu(bpy)]²⁺ cations, a weakly coordinated water molecule and perchlorate ions. In each binuclear unit, Cu1, coordinated by four nitrogen atoms of the macrocyclic organic ligand is connected to Cu2 via the exo-cis oxygen atoms of the macrocyclic ligand with Cu···Cu separations of 5.151?Å; Cu2 assumes square-pyramidal geometry. Magnetic properties measured at 2–300?K show antiferromagnetic exchange between adjacent copper(II) ions.     

Tricyclic ligands on cyclam core and X-ray crystallographic structure of hexachloro-(1,11:4,8-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,8-diazonia-4,11-diazacyclotetradecane) - dimanganese(II) dimethanol dihydrate solvate

The synthesis of tricyclic compounds on functionalized cyclam core is described. The addition of four methyl acrylate molecules and consecutive condensation of this derivative with ethylenediamine resulted in formation of 1,4,8,11-tetrakis(2-(N-(2-aminoethyl)carbamoyl)ethyl)-1,4,8,11-tetraazacyclotetradecane (3). Compound 3 was the substrate for further condensation with dialdehydes: iso-phthaldialdehyde and 2,6-pyridinedicarbaldehyde, resulting in spontaneous macrocycle ring closure to give tricyclic derivatives: 1,11:4,8-bis(benzene-1,3-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (4) in the reaction of 3 with iso-phthaldialdehyde and three isomers: 1,4:8,11-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (5A), 1,11:4,8-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (5B), and 1,8:4,11-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (5C) when 2,6-pyridinedicarbaldehyde was used. The compounds 4, 5B, and 5C were identified crystallographically. The isolated 5A converted in solution into the mixture of 5B and 5C as monitored by the ¹H NMR spectroscopy. The tricycle 5 is able to accept two manganese(II) metal ions by reacting with manganese(II) dichloride with simultaneous diprotonation of 5. Structure of the resulting Mn₂(5BH₂)Cl₆·(CH₃OH)₂(H₂O)₂ was determined crystallographically.     

Physical Image vs. Structure Relation. Part 3 [1]. Basic Properties and Protonation Mechanism of Some Tetraaza Macrocyclic Ligands

The protonation constants, log K, for 1,4,7,11-tetraazacyclotetradecane (isocyclam, 2), 1-(2-aminoethyl)-1,4,8,11-tetraazacyclotetradecane (scorpiand, 3), 5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane (Me₂cyclam, 4) and 5,5,7,12,14,14-hexamethyl-1,4,8,11- tetraazacyclotetradecane (Me₆cyclam, 5) were determined pH-metrically. Attempts of correlation of the calculated enthalpy of protonation in the gas phase (AM1 method) with experimental values of the protonation constants for ligands 1, 2, 4–7 were done 1,4,8,11-tetraazacyclotetradecane, cyclam, 1; 1,4,7,10-tetraazacyclotetradecane, cyclen, 6; 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, (N-Me)₄cyclam, 7. Extensive NMR pH-titrations, i.e., determination of pH vs. chemical shifts (¹H and/or ¹³C) plots, (_X = f(pH), allowed to suggest the most likely protonation schemes of all nitrogen atoms in the cyclic polyamines 1–3. The possibility of the formation-breaking of the intramolecular hydrogen bonds, as well as the change of conformation of these polybasic macrocycles during protonation-deprotonation steps, has been considered on the basis of the supplementary theoretical calculations (MMX/STO-3G study).     

Poly(propylene imine) dendrimer complexes of Cu(II), Zn(II), and Co(III) as catalysts of hydrolysis of p-nitrophenyl diphenyl phosphate

Poly(propylene imine) dendrimers having 8, 32, and 64 primary amine end groups form diamino Cu(II), diamino Zn(II), and tetramino Co(III) complexes that are identified spectrophotometrically and titrimetrically. The dendrimer–metal ion complexes catalyze the hydrolysis of p-nitrophenyl diphenyl phosphate in zwitterionic buffer solutions at pH ≤ 8.1 with relative activities Cu(II) > Zn(II) > Co(III). The rates of hydrolysis are faster with sodium perchlorate than with sodium chloride to control ionic strength. In sodium perchlorate solutions with Cu(II) the rates increase with increasing size of the dendrimer. In sodium chloride solutions with Cu(II) the rates decrease with increasing size of the dendrimer. Rate constants in buffered sodium chloride solutions of dendrimers and 1.0mM Cu(II) are 1.3–6.3 times faster than in the absence of Cu(II). The fastest hydrolyses occurred at a dendrimer primary amine to Cu(II) ratio NH₂/Cu ≤ 2. At NH₂/Cu = 4 and with the 1,4,7,10-tetraazacyclodecane complex of Cu(II) hydrolysis rates were much slower. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2727–2736, 1999     

Synthesis and Characterization of Ni(II), Cu(II), Zn(II) and Cd(II) Complexes of a New Vic-Dioxime Ligand

In this study, 1,2-dihydroxyimino-3,7-di-aza-9,10-O-α-methyl benzal decane (LH₂) was synthesized starting from 1,2-O-α-methyl benzal-4-aza-7-amino heptane (RNH₂) and antichloroglyoxime. With this ligand, complexes were synthesized using Ni(II) and Cu(II) salts with a metal:ligand ratio of 1:2. However, the reaction of the ligand with salts of Zn(II) and Cd(II) gave products with metal:ligand ratio of 1:1. Structures of the ligand and its complexes are proposed based on elemental analyses, IR, ¹³C- and ¹H-NMR spectra, magnetic susceptibility measurements and thermogravimetric analyses (TGA).     

Synthesis, crystal structure, spectroscopic and photoluminescence studies of manganese(II), cobalt(II), cadmium(II), zinc(II) and copper(II) complexes with a pyrazole derived Schiff base ligand

Varying coordination modes of the Schiff base ligand H₂L [5-methyl-1-H-pyrazole-3-carboxylic acid (1-pyridin-2-yl-ethylidene)-hydrazide] towards different metal centers are reported with the syntheses and characterization of four mononuclear Mn(II), Co(II), Cd(II) and Zn(II) complexes, [Mn(H₂L)(H₂O)₂](ClO₄)₂(MeOH) (1), [Co(H₂L)(NCS)₂] (2), [Cd(H₂L)(H₂O)₂](ClO₄)₂ (3) and [Zn(H₂L)(H₂O)₂](ClO₄)₂ (4), and a binuclear Cu(II) complex, [Cu₂(L)₂](ClO₄)₂ (5). In the complexes 1-4 the neutral ligand serves as a 3N,2O donor where the pyridine ring N, two azomethine N and two carbohydrazine oxygen atoms are coordinatively active, leaving the pyrazole-N atoms inactive. In the case of complex 5, each ligand molecule behaves as a 4N,O donor utilizing the pyridine N, one azomethine N, the nitrogen atom proximal to the azomethine of the remaining pendant arm and one pyrazole-N atom to one metal center and the carbohydrazide oxygen atom to the second metal center. The complexes 1-4 are pentagonal bipyramidal in geometry. In each case, the ligand molecule spans the equatorial plane while the apical positions are occupied by water molecules in 1, 3 and 4 and two N bonded thiocyanate ions in 2. In complex 5, the two Cu(II) centers have almost square pyramidal geometry (τ = 0.05 for Cu1 and 0.013 for Cu2). Four N atoms from a ligand molecule form the basal plane and the carbohydrazide oxygen atom of a second ligand molecule sits in the apex of the square pyramid. All the complexes have been X-ray crystallographically characterized. The Zn(II) and Cd(II) complexes show considerable fluorescence emission while the remaining complexes and the ligand molecule are fluorescent silent.     

Bioactive Co(II), Ni(II), and Cu(II) Complexes Containing a Tridentate Sulfathiazole-Based (ONN) Schiff Base

New Co(II), Ni(II), and Cu(II) complexes were synthesized with the Schiff base ligand obtained by the condensation of sulfathiazole with salicylaldehyde. Their characterization was performed by elemental analysis, molar conductance, spectroscopic techniques (IR, diffuse reflectance and UV–Vis–NIR), magnetic moments, thermal analysis, and calorimetry (thermogravimetry/derivative thermogravimetry/differential scanning calorimetry), while their morphological and crystal systems were explained on the basis of powder X-ray diffraction results. The IR data indicated that the Schiff base ligand is tridentate coordinated to the metallic ion with two N atoms from azomethine group and thiazole ring and one O atom from phenolic group. The composition of the complexes was found to be of the [ML₂]∙nH₂O (M = Co, n = 1.5 (1); M = Ni, n = 1 (2); M = Cu, n = 4.5 (3)) type, having an octahedral geometry for the Co(II) and Ni(II) complexes and a tetragonally distorted octahedral geometry for the Cu(II) complex. The presence of lattice water molecules was confirmed by thermal analysis. XRD analysis evidenced the polycrystalline nature of the powders, with a monoclinic structure. The unit cell volume of the complexes was found to increase in the order of (2) < (1) < (3). SEM evidenced hard agglomerates with micrometric-range sizes for all the investigated samples (ligand and complexes). EDS analysis showed that the N:S and N:M atomic ratios were close to the theoretical ones (1.5 and 6.0, respectively). The geometric and electronic structures of the Schiff base ligand 4-((2-hydroxybenzylidene) amino)-N-(thiazol-2-yl) benzenesulfonamide (HL) was computationally investigated by the density functional theory (DFT) method. The predictive molecular properties of the chemical reactivity of the HL and Cu(II) complex were determined by a DFT calculation. The Schiff base and its metal complexes were tested against some bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The results indicated that the antibacterial activity of all metal complexes is better than that of the Schiff base.     

Synthesis and photoluminescent properties of a Schiff-base ligand and its mononuclear Zn(II), Cd(II), Cu(II), Ni(II) and Pd(II) metal complexes

Mononuclear Zn(II), Cd(II), Cu(II), Ni(II) and Pd(II) metal complexes of Schiff-base ligand(HL₁) derived from 8-acetyl-7-hydroxycoumarin and P-phenylenediamine were prepared and characterized by microanalytical, mass, UV–Vis, IR, ¹H NMR, ¹³C NMR, ESR, conductance and fluorescence studies. The measured low molar conductance values in DMSO indicate that the complexes are non-electrolytes. The structures of the solid complexes under study are established by using IR, electronic and ESR spectroscopy suggesting that Zn(II) and Ni(II) complexes are octahedral, Cd(II) complex is tetrahedral, Cu(II) and Pd(II) complexes are square planar. The ESR spectrum of the Cu(II) complex in DMSO at 298 and 150 K was recorded and its salient features are reported, it supports the mononuclear structure. The Schiff base exhibited photoluminescence originating from intraligand (π–π*) transitions. Metal-mediated enhancement is observed on complexation of HL with Zn(II) and Cd(II), whereas metal-mediated fluorescence quenching occurs in Cu(II), Ni(II) and Pd(II).     

Synthesis,characterization, and in vitro antiproliferative and antibacterial studies of tetraazamacrocyclic complexes of Co(II) and Cu(II) with pyromellitic acid

New cationic tetranuclear Co(II) and neutral binuclear Cu(II) complexes with tpmc (N,N′,N″,N″′-tetrakis-(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane) and bridging pyromellitate ligand pma (tetraanion 1,2,4,5-benzenetetracarboxylic acid) were isolated. The composition of the compounds is proposed based on elemental analyses (C, H, N, M=Cu, Co), molar conductivity determination, UV-Vis, FTIR, EPR, LC-MS and reflectance spectroscopy, magnetic measurements, cyclic voltammetry, as well as TG and DTA. It is proposed that in [Co₄(pma)(tpmc)₂](ClO₄)₄·6H₂O (1), cobalt(II) is six-coordinate out of cyclam rings and one OCO^? from pma participates in coordination with one Co(II). In the case of [Cu₂(pma)tpmc]?8H₂O (2), one OCO^? from pma bridges two Cu(II). The cytotoxic activity of 1 and 2 was tested against tumor cell lines human cervix adenocarcinoma (HeLa), estrogen-receptor-positive human breast cancer (MCF-7), human myelogenous leukemia (K562), and the human Caucasian Burkitt’s lymphoma (Ramos). The IC₅₀ values for 1 and 2 were within the range 44.66 ± 2.39 to 152.40 ± 2.28 μM, and from 140.88 ± 3.51 to 192.05 ± 2.09 μM, respectively. Both 1 and 2 were tested for antimicrobial activity. We determined that minimal inhibitory concentration for 1 against Staphylococcus aureus, Bacillus subtilis, and Klebsiella pneumoniae was 25 mM. Complex 2 did not express activity against tested microbial strains.     

Hg(II), Tl(III), Cu(I), and Pd(II) Complexes with 2,2'-Diphenyl-4,4'-Bithiazole (DPBTZ), Syntheses and X-Ray Crystal Structure of [Hg(DPBTZ)(SCN)2]

Reaction of the ligand 2,2′-diphenyl-4,4′-bithiazole (DPBTZ) with Hg(SCN)₂, Tl(NO₃)₃, CuCl, and PdCl₂ gives complexes with stoichiometry [Hg(DPBTZ)(SCN)₂], [Tl(DPBTZ)(NO₃)₃], [Cu(DPBTZ)(H₂O)Cl]_, and [Pd(DPBTZ)Cl₂]. The new complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of [Hg(DPBTZ)(SCN)₂] determined by X-ray crystallography. The Hg atom in the title monomeric complex, (2,2′-diphenyl-4,4′-bithiazole)mercury(II)bisthiocyanate, [Hg(C₁₈H₁₂N₂S₂)(SCN)₂], is four-coordinate having an irregular tetrahedral geometry composed of two S atoms of thiocyanate ions [Hg-S 2.4025(15) and 2.4073(15) Å] and two N atoms of 2,2′-diphenyl-4,4′-bithiazole ligand [Hg-N 2.411(4) and 2.459(4) Å]. The bond angle S(3)-Hg(1)-S(4) of 147.46(5)° has the greatest derivation from ideal tetrahedral geometry. Intermolecular interaction between Hg(1) and two S atoms of two neighboring molecules, 3.9318(15) and 3.9640(18) Å, make the Hg(1) distort from a tetrahedron to a disordered octahedron. The attempts for preparation complexes of Tl(I), Pb(II), Bi(III), Cd(II) ions with 2,2′-diphenyl-4,4′-bithiazole ligand were not successful and also the attempts for preparation complexes of 4,4′,5,5′-tetraphenyl-2,2′-bithizole ligand with Cu(II), Ni(II), Co(II), Co(III), Mn(II), Mn(III), Fe(II), Fe(III), Cr(III), Zn(II), Tl(III), Pb(II), Hg(II), Cu(I), Pd(II) were not successful. This point can be regarded as the initial electron withdrawing of phenyl rings and also their spatial steric effects.     

Dinaphthotetraaza[14]annulene copper(II) complexes in the electrocatalytic reduction of carbon dioxide and bisulfite anion

A modified synthetic route for the complexes [Cu(II)5,7,12,14-tetramethyldinaphtho [b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)tmdnTAA], and [Cu(II) 5,7,12,14-tetramethyl-6,13-dichloro-dinaphtho[b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)dCltmdnTAA], is presented in this work. The electrochemical characterization of both complexes and their precursors, [bis(2,4-pentanedionato)copper(II)], [Cu(II)(acac)₂] and [bis(3-chloro-2,4-pentanedionato)copper(II)], [Cu(II)(3-Cl-acac)₂], respectively, under nitrogen and carbon dioxide is also presented. The voltammetric response of [Cu(II)(acac)₂] and [Cu(II)(3-Cl-acac)₂] are different compared to [Cu(II)tmdnTAA] and [Cu(II)dCltmdnTAA] under nitrogen. Precursors show the reduction of Cu(I) to Cu(0) and the tetraazadinaphtho[14]annulene complexes do not. The chlorine substituted complex has a lower reduction potential than the unsubstituted homologue under nitrogen atmosphere. However, the contrary response is obtained in the presence of carbon dioxide: the unsubstituted complex is more catalytic in terms of potential because the current discharge appears 270?mV shifted to the anodic region. These facts can be explained in terms of electronic and steric effects. The modified electrode obtained by oxidative electropolymerization of [Cu(II)tmdnTAA] over glassy carbon electrode presented a suitable amperometric response for the sulfite reduction in acidic medium (pH?=?2.7). A linear correlation was observed for the catalytic current and sulfite concentration between 0.6–6.0?mM range.     

Synthesis,characterization, and anticancer activity of some azole‐heterocyclic complexes with gold(III), palladium(II), nickel(II), and copper(II) metal ions

Four new complexes of Au(III), Pd(II), Ni(II), and Cu(II) ions were synthesized, derived from a novel heterocyclic ligand (L) that has both triazole and tetrazole rings. The ligand synthesis was through successive steps to achieve both heterocyclic rings. The synthesized compounds were characterized using conventional techniques like infrared, ultra violet—visible and proton/carbon nuclear magnetic resonance spectroscopy, metal and thermal analyses, and molar conductivity. All complexes were suggested to have square planar geometry, gold, nickel, and palladium complexes were salts while copper neutral complexes have the chemical formulas; [AuL₂]Cl.2H₂O, [PdL₂]Cl₂.2H₂O, [NiL₂]Cl₂.2H₂O, and [CuL₂]. The cytotoxic effect was studied on breast cancer cell line (MCF‐7 cell line) at different concentrations by using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay method, for the ligand (L) and complexes. The results showed that gold(III) and nickel(II) complexes have the highest cytotoxicity among all compounds against cancer cell lines.     

Synthesis and magnetic properties of binuclear cobalt(Ⅱ), nickel(Ⅱ) and copper(Ⅱ) complexes bridged by oxamidate group

Four binuclear Co(Ⅱ), Ni(Ⅱ) and Cu(Ⅱ) complexes bridged by oxamidate (oxd) group have been synthesized, namely Co2(byp)2(oxd)(ClO4)2 (1), Co2(Me2bpy)2(oxd)(ClO4)2.H2O (2), Ni2(bpy)2(oxd)(ClO4)2.2H2O (3) and Cu2(Me2bpy)2(oxd)(NO3)2 (4). (bpy=2,2'-bipyridyl, Me2-bpy=4,4'-dimethylbipyridyl, oxd=oxamidate) The complexes are characterized by IR, UV spectra, EPR and variable-temperature magnetic susceptibility (4-300 K). The susceptibility data for. complexes 1 and 3 were least-squares fit to the susceptibility equation derived from the spin Hamiltonian H=-2J . S1 . S2. The exchange integral, J, was found to be equal to -3.62 cm-1 in 1 and -1.82 cm-1 in 3. This indicates a weak antiferromagnetic spin exchange interaction between the metal ions.     

SEVERAL COORDINATION MODES OF 5-AMINO-1,3,4-THIADIAZOLE-2-SULFONAMIDE (HATS) WITH Cu(II), Ni(II) AND Zn(II): MIMETIC TERNARY COMPLEXES OF CARBONIC ANHYDRASE-INHIBITOR

Abstract

The coordination properties of 5-amino-1,3,4-thiadiazole-2-sulfonamide (Hats) with Cu(II), Ni(II) and Zn(II) ions, are analyzed. Although the ligand presents several donor atoms, we have only observed three coordination behaviors: (i) as a monodentate ligand through the N_sulfonamido atom, (ii) as a bridging ligand linking the metal ions through the N_sulfonamido and N_thiadizole atoms and (iii) as a bridging ligand linking metal ions through the N and O atoms of the sulfonamidate group. It is noteworthy that coordination mode (iii) is observed for the first time in heterocyclic sulfonamides complexes. In addition, the conformation of the Hats as counter-ion is analyzed and compared with the conformations that the ligand adopts in metal complexes.     

Co(II), Ni(II), Cu(II) and Zn(II) complexes of aminothiazole‐derived Schiff base ligands: Synthesis,characterization, antibacterial and cytotoxicity evaluation,bovine serum albumin binding and density functional theory studies

Transition metal complexes of type M(L)₂(H₂O)_x were synthesized, where L is deprotonated Schiff base 2,4‐dihalo‐6‐(substituted thiazol‐2‐ylimino)methylphenol derived from the condensation of aminothiazole or its derivatives with 2‐hydroxy‐3‐halobenzaldehyde and M = Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ (x = 0 for Cu²⁺ and Zn²⁺; x = 2 for Co²⁺ and Ni²⁺). The synthesized Schiff bases and their metal complexes were thoroughly characterized using infrared, ¹H NMR, electronic and electron paramagnetic resonance spectroscopies, elemental analysis, molar conductance and magnetic susceptibility measurements, thermogravimetric analysis and scanning electron microscopy. The results reveal that the bidentate ligands form complexes having octahedral geometry around Co²⁺ and Ni²⁺ metal ions while the geometry around Cu²⁺ and Zn²⁺ metal ions is four‐coordinated. The geometries of newly synthesized Schiff bases and their metal complexes were fully optimized in Gaussian 09 using 6–31 + g(d,p) basis set. Fluorescence quenching data reveal that Zn(II) and Cu(II) complexes bind more strongly to bovine serum albumin in comparison to Co(II) and Ni(II) complexes. The ligands and their complexes were evaluated for in vitro antibacterial activity against Escherichia coli ATCC 25922 (Gram negative) and Staphylococcus aureus ATCC 29213 (Gram positive) and cytotoxicity against lever hepatocellular cell line HepG2.