Divalent transition metal complexes of 3,5-pyrazoledicarboxylate

New divalent transition metal 3,5-pyrazoledicarboxylate hydrates of empirical formula Mpz(COO)₂(H₂O)₂, where M=Mn, Co, Ni, Cu, Zn and Cd (pz(COO)₂=3,5-pyrazoledicarboxylate), metal hydrazine complexes of the type Mpz(COO)₂N₂H₄ where M=Co, Zn or Cd and Mpz(COO)₂nN₂H₄·H₂O, where n=1 for M=Ni and n=0.5 for M=Cu have been prepared and characterized by physico-chemical methods. Electronic spectroscopic data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of unidentate carboxylate anion (Δν=ν_asy(COO^–)–ν_sym(COO^–)>215 cm^–1) in all the complexes and bidentate bridging hydrazine (ν_N–N=985–950 cm^–1) in the metal hydrazine complexes. Both metal carboxylate and metal hydrazine carboxylate complexes undergo endothermic dehydration and/or dehydrazination followed by exothermic decomposition of organic moiety to give the respective metal oxides as the end products except manganese pyrazoledicarboxylate hydrate, which leaves manganese carbonate. X-ray powder diffraction patterns reveal that the metal carboxylate hydrates are isomorphous as are those of metal hydrazine complexes of cobalt, zinc and cadmium.     

Synthesis,characterization and anti-bacterial activity of divalent transition metal complexes of hydrazine and trimesic acid

Transition metal complexes of trimesic acid and hydrazine mixed-ligands with a general formula M(Htma)(N₂H₄)₂, where, M = Mn, Co, Ni, Cu and Zn; H₃tma = trimesic acid, have been prepared and characterized by elemental, structural, spectral and thermal analyses. For the complexes, the carboxylate ν_asym and ν_sym stretchings are observed at about 1626 and 1367 cm^?1 respectively, with Δν between them of ～260 cm^?1, showing the unidentate coordination of each carboxylate group. The hydrazine moieties are present as bridging bidentates. Electronic and EPR spectral studies suggest an octahedral geometry for the complexes. All these complexes show three steps of decomposition in TGA/DTA. SEM images of CuO and MnO residues obtained from the complexes show nano-sized clusters suggesting that the complexes may be used as precursors for nano-CuO and nano-MnO preparation. The antimicrobial activities of the prepared complexes, against four bacteria have been evaluated.     

Coordination and inclusion compounds formed by addition of quinoline (Q) or isoquinoline (Iq) to a metal(II) dibenzoylmethanate (Co, Ni, Zn, Cd)

Three isomorphous series of new compounds are reported: complexes [M(DBM)₂Q₂] and [M(DBM)₂Iq₂] (M = M(II) = Co, Ni, Zn, Cd; DBM is C₆H₅COCHCOC₆H₅ ^?) and inclusion compounds [M(DBM)₂Q₂]*Q (M = Co, Zn, Cd). All the compounds comprise a trans configured octahedral complex molecule. Inclusion compounds of modified Zn and Cd DBM complexes are reported for the first time and their inclusion ability is attributed to the trans isomeric state induced by the bulky Q or Iq ligand. The TG measurements indicate the following order of thermal stability of the complexes defined by the strength of the metal–ligand bonds: Ni > Co > Cd > Zn. The inclusion compounds do not follow this trend.     

Synthesis and characterisation of Co(II), Ni(II), Zn(II) and Cd(II) complexes with 5-bromo-N,N′-bis-(salicylidene)-o-tolidine

New complexes of type [M(HL)(CH₃COO)(OH₂)_m]·nH₂O (where M:Co, m = 2, n = 2; M:Ni, m = 2, n = 1.5; M:Zn, m = 0, n = 2.5 and M:Cd, m = 0, n = 0; H₂L:5-bromo-N,N′-bis-(salicylidene)-o-tolidine) have been synthesized and characterized by microanalytical, IR, UV–Vis-NIR and magnetic data. Electronic spectra of Co(II) and Ni(II) complexes are characteristic for an octahedral stereochemistry. The IR spectra indicate a chelate coordination mode for mono-deprotonated Schiff base and a bidentate one for acetate ion. The thermal transformations are complex according to TG and DTA curves including dehydration, acetate decomposition and oxidative degradation of the Schiff base. The final product of decomposition is the most stable metallic oxide.     

Spectroscopic and antimicrobial studies of macrocyclic metal complexes derived from 1,8-diaminonaphthalene and dimedone

A new series of macrocyclic metal complexes have been synthesized and characterized by the template condensation reaction of 1,8-diaminonaphthalene and dimedone in presence of divalent transition metals, resulting into the formation of the macrocyclic complexes of the type: [M(C₃₆H₃₆N₄)X₂]; where M = Co(II), Ni(II), Cu(II), Zn(II) and X = Cl^?, NO₃ ^?, CH₃COO^?. The synthesized macrocyclic complexes have been characterized with the aid of elemental analysis, conductance measurements, magnetic susceptibility measurements, electronic, infrared, NMR, Mass and ESR spectral studies. The complexes were also investigated for their fluorescence activity. Electronic spectra along with magnetic moments suggest the six coordinated octahedral geometry for all these complexes. The low value of molar conductance indicates them to be non-electrolyte. The in vitro antimicrobial activities of these macrocyclic complexes have also been investigated against some bacterial strains and yeast. Further minimum inhibitory concentration shown by these complexes against these pathogens was compared with MIC shown by standard antibiotic and standard antifungal drug.     

Synthesis, spectral and thermal studies of N,N − -pyridine-2,6-diyl bis[N −-phenyl(thiourea)] and its metal complexes

Four new metal complexes with the general formula, [ML·mH₂O]nH₂O (where, M = Cu(I), Co(II), Ni(II) or Zn(II); L = N,N ^?-pyridine–2,6-diyl bis[N ^?-phenyl (thiourea)] (PDPT); m = 1 or 3 and n = 0.5 or 4.0), have been synthesized and characterized by elemental analyses, spectral analyses (IR, UV–Vis., ¹H-NMR and MS), thermal analyses (TGA), conductivity and magnetic measurements. The results showed that the ligand (PDPT) acts in a mononegative tridentate manner towards Cu(I) ion coordinating via the two thiol sulfurs and pyridyl nitrogen groups with displacement of only one hydrogen atom from the thiol group, while the ligand behaves in a binegative tridentate manner towards the Co(II), Ni(II) and Zn(II) ions with displacement of two hydrogen atoms from the two thiol groups. The value of magnetic measurements showed a diamagnetic character of the copper complex indicating the reduction of Cu(II) to Cu(I). Semi-empirical calculations of the ligand and its metal complexes have been used to study the molecular geometry using ZINDO/1, PM3 and AM1. Also, the harmonic vibration spectra of the ligand and its metal complexes have been investigated with the purpose to assist the experimental assignment of metal complexes. The results of the optical absorption studies reveal that the optical transition is direct with band gaps energy (E_g) values 2.62, 1.98 and 1.85 eV for Cu, Co and Ni complexes, respectively, indicating that these complexes can behave as semi-conductors.     

Characterization and TG-MS studies of lactato and bipyridine-lactato complexes of Co(II) and Ni(II)

Two lactates and four new mixed ligand complexes with formulae Co(lact)₂·2H₂O, Ni(lact)₂·3H₂O, Co(4-bpy)(lact)₂, Co(2,4'-bpy)₂(lact)₂, Ni(4-bpy)(lact)₂·2H₂O and Ni(2,4'-bpy)₂(lact)₂ (where 4-bpy=4,4'-bipyridine, 2,4'-bpy=2,4'-bipyridine, lact=CH₃CH(OH)COO^-) were isolated and investigated. The thermal behaviour of compounds was studied by thermal analysis (TG, DTG, DTA). In the case of hydrated complexes thermal decomposition starts with the release of water molecules. The compounds decompose at high temperature to metal(II) oxides in air. A coupled TG-MS system was used to analyse the principal volatile products of thermolysis and fragmentation processes of obtained complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mononuclear transition and non-transition complexes of amlodipine besylate as antihypertensive agent: synthesis,spectral, thermal,and antimicrobial studies

Mononuclear Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Mg(II), Sr(II), Ba(II), Ca(II), Pt(IV), Au(III), and Pd(II) complexes of the drug amlodipine besylate (HL) have been synthesized and characterized by elemental analysis, spectroscopic technique (IR, UV–Vis, solid reflectance, scanning electron microscopy, X-ray powder diffraction, and ¹H-NMR) and magnetic measurements. The elemental analyses of the complexes are confirmed by the stoichiometry of the types [M(HL)(X)₂(H₂O)]·nH₂O [M = Mn(II), Co(II), Zn(II), Ni(II), Mg(II), Sr(II), Ba(II), and Ca(II); X = Cl^? or NO₃ ^?], [Cd(HL)(H₂O)]Cl₂, [Pd(HL)₂]Cl₂, [Pt(L)₂]Cl₂, and [Au(L)₂]Cl, respectively. Infrared data revealed that the amlodipine besylate drug ligand chelated as monobasic tridentate through NH₂, oxygen (ether), and OH of besylate groups in Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Mg(II), Sr(II), Ba(II), Ca(II), and Au(III) complexes, but in Pt(IV) and Pd(II) complexes, the amlodipine besylate coordinates via NH₂ and OH (besylate) groups. An octahedral geometry is proposed for all complexes except for the Cd(II), Pt(IV), and Pd(II) complexes. The amlodipine besylate free ligand and the transition and non-transition complexes showed antibacterial activity towards some Gram-positive and Gram-negative bacteria and the fungi (Aspergillus flavus and Candida albicans).     

Novel Co(II) and Cd(II) complexes with non-steroidal anti-inflammatory drugs

New metal(II) complexes with empirical formulae Co(ibup)₂·4H₂O, Cd(ibup)₂·3H₂O, Co(nap)₂·H₂O, Cd(nap)₂·3H₂O (where ibup=(CH₃)₂CHCH₂C₆H₄CH(CH₃COO⁻) and nap=CH₃O(C₁₀H₆)CH(CH₃COO⁻)) were isolated and investigated. The complexes were characterized by elemental analysis, molar conductance, IR spectroscopy and thermal decomposition. The thermal behavior was studied by TG, DTG, DTA methods under non-isothermal conditions in air atmosphere. The hydrated complexes lose water molecules in first step. All complexes decompose via intermediate products to corresponding metal oxides CoO and CdO. A coupled TG-MS system was used to detect the principal volatile products of thermolysis and fragmentation processes of Co(nap)₂·H₂O. The IR spectra of studied complexes revealed also absorption of the carboxylate group. Principal concern with the position of asymmetric, symmetric frequencies. The value of their separation allow to deduce about type of coordination these groups.     

Thermal behaviour and spectroscopic investigation of some methyl 2-pyridyl ketone complexes

Pyridine derivative complexes are widely employed as biological active materials especially as antibacterial agents. Five transition metal(II) mpk complexes (mpk = methyl 2-pyridyl ketone) were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV–Vis–NIR) and conductometric measurements. The general formulae established from experimental data were found to be [M(mpk)₂(NO₃)₂]·xH₂O (x = 0 for M = Cd(II), Zn(II), x = 2 for M = Cu(II)) and [M(mpk)₂(H₂O)₂](NO₃)₂ (M = Co(II), Ni(II)). These compositions were further confirmed by thermal analysis and their thermal stability in dynamic air atmosphere investigated.     

Synthesis, spectral and thermal studies of new copper (II) complexes with 1,2-di(imino-2-aminomethylpyridil)ethane

New copper (II) complexes of Schiff bases with 1,2-di(imino-2-aminomethylpyridil)ethane with the general composition CuLX _m (H₂O) _x , [L = Schiff base, X = Cl^?, Br^?, NO₃ ^?, ClO₄ ^?, CH₃COO^?, m = 2; X = SO₄ ^2?, m = 1] were prepared by template synthesis. The complexes were characterized by elemental analysis, conductivity measurements, magnetic moments, IR, UV–VIS and EPR spectra. The thermal behavior of complexes was studied using thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Infrared spectra of all complexes are in good agreement with the coordination of a neutral tetradentate N₄ ligand to the cooper (II) through azomethinic and pyridinic nitrogen. Magnetic, EPR and electronic spectral studies show a monomeric distorted octahedral geometry for all Cu(II) complexes. Conductance measurements suggest the non-electrolytic nature of the compounds, except for copper (II) nitrate and perchlorate complexes which are 1:2 electrolytes. Heats of decomposition, ΔH, associated with the exothermal effects were also determined.     

Novel complexes of Co2+, Ni2+, and Cu2+ with N-(phosphonomethyl)aminosuccinic acid

Complexes of Co²⁺, Ni²⁺, and Cu²⁺ with N-(phosphonomethyl)aminosuccinic acid (H₄PMAS) of general formula Na₂MPMAS·nH₂O [M=Co(II), Ni(II), Cu(II), n—number of water molecules] were synthesized. Based on interpretation of diffusion reflectance spectroscopy, structure of all complexes is based on distorted octahedral. Analysis of IR spectra of Co(II), Ni(II), and Cu(II) N-(phosphonomethyl)aminosuccinates demonstrated that metal ions are coordinated to the ligand through nitrogen atom of the imino group, oxygen atoms of the α- and β-carboxyl groups as well as oxygen atom of the phosphonic group of the H₄PMAS. We demonstrated that thermal stability of complexes increases in sequence Cu(II) < Ni(II) < Co(II), obviously as a result of change over from the dimeric to polymeric character of the initial complex. Complete decomposition of ligand occurs at these temperatures and is accompanied by release of H₂O, CO₂, and NO₂. The final products of thermal decomposition of the complexes are mixtures of oxides and phosphates of respective metals.     

Mixed Ligand Complex Formation of Cetirizine Drug with Bivalent Transition Metal(II) Ions in the Presence of 2-Aminomethylbenzimidazole: Synthesis,Structural, Biological,pH-Metric and Thermodynamic Studies

Mononuclear copper(II), cobalt(II) and nickel(II) complexes of cetirizine (CTZ = 2-[2-[4-[(4-chlorophenyl)phenyl methyl]-piperazine-1-yl]-ethoxy]acetic acid) in the presence of 2-aminomethyl-benzimidazole·2HCl (AMBI), as a representative example of heterocyclic bases, were synthesized and studied by different physical techniques. All mixed-ligand complexes have been fully characterized with the help of elemental analyses, molecular weight determinations, molar conductance, magnetic moments and spectroscopic data. The formulae of the isolated complexes are [M(AMBI)(CTZ)(NO₃)(H₂O)₂]·nH₂O where AMBI is the neutral bidentate 2-aminomethylbenzimidazole, CTZ the deprotonated cetirizine and n = 1 for Co(II) or 0 for Cu(II) and Ni(II) complexes. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytes. The formation equilibria of the ternary complexes have been investigated. Ternary complexes are formed by a simultaneous mechanism. Stoichiometry and stability constants for the complexes formed are reported. The concentration distribution of the complexes in solution was evaluated as a function of pH. The thermodynamic parameters were calculated from the temperature dependence of the equilibrium constants and are discussed. The synthesized metal chelates have been screened for their antimicrobial activities against the selected types of Gram-positive (G⁺) and Gram-negative (G^?) bacteria. They were found to be more active against Gram positive than Gram negative bacteria. The antimicrobial activity in terms of metal ions obeys this order: Cu(II) > Ni(II) > Co(II).     

Synthesis, characterization and electro-spectroelectrochemical studies of four macrocyclic Schiff-base Co(II) complexes having N2O2 set of donor atoms

Four macrocyclic Schiff-base cobalt complexes, [CoL¹][NO₃]₂ · 3H₂O, [CoL²][NO₃]₂ · 4H₂O, [CoL³][NO₃]₂ · 4H₂O and [CoL⁴][NO₃]₂ · 2H₂O, were synthesized by reaction of salicylaldehyde derivatives with 1,4-bis(3-aminopropoxy)butane or (±)-trans-1,2-diaminocyclohexane and Co(NO₃)₂ · 6H₂O by template effect in methanol. The metals to ligand ratio of the complexes were found to be 1:1. The Co(II) complexes are proposed to be tetrahedral geometry. The macrocyclic Co(II) complexes are 1:2 electrolytes as shown by their molar conductivities (Λ_M) in DMF (dimethyl formamide) at 10^?3 M. The structure of Co(II) complexes is proposed from elemental analysis, Ft-IR, UV–visible spectra, magnetic susceptibility, molar conductivity measurements and mass spectra. Electrochemical and thin-layer spectroelectrochemical studies of the complexes were comparatively studied in the same experimental conditions. The electrochemical results revealed that all complexes displayed irreversible one reduction processes and their cathodic peak potential values (E _pc) were observed in around of ?1.14 to 0.95 V. It was also seen that [CoL¹][NO₃]₂ · 3H₂O and [CoL²][NO₃]₂ · 4H₂O exhibited one cathodic wave without corresponding anodic wave but, [CoL³][NO₃]₂ · 4H₂O and [CoL⁴][NO₃]₂ · 2H₂O showed one cathodic wave with corresponding anodic wave, probably due to the presence of different ligand nature even if the complexes have the same N₂O₂ donor set. In view of spectroelectrochemical studies [CoL³][NO₃]₂ · 4H₂O showed distinctive spectral changes in which the intensity of the band (λ = at 316 nm, assigned to n → π* transitions) decreased and a new broad band in a low intensity about 391 nm appeared as a result of the reduction process based on the cobalt center in the complex.     

Effective reduction of <Emphasis Type="Italic">p</Emphasis>-nitrophenol catalyzed by nickel(II) adamantane complexes

Two Ni(II) adamantane complexes, [Ni(bqad)Cl₂] (1) and [Ni(bpad)(dmbp)(H₂O)](ClO₄)₂·CH₃OH H₂O (2) (bqad = N,N′-bis(2-quinolinylmethyl) amantadine, bpad = N,N′-bis(2-pyridylmethyl)amantadine, dmbp = 5,5′-dimethyl-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, infrared spectroscopy and single crystal X-ray diffraction. The nickel centers in complex 1 have a distorted tetragonal pyramidal geometry, while the coordination polyhedron of 2 can be described as a distorted octahedron. The reaction kinetics for reduction of p-nitrophenol to p-aminophenol catalyzed by these complexes has been investigated by UV–visible spectrophotometry. Complex 1 exhibits a higher turnover frequency of 1.4 min^?1 for the reduction of p-nitrophenol.     

Polyoxidovanadate complexes: synthesis,structures and catalytic oxidative bromination of phenol red

By selecting appropriate ligands, two polyoxidovanadate complexes, [Ni(en)₂]₃[V₁₈O₄₂Cl]·7H₂O·2H₃O⁺ (1) and [H₂N(CH₃)₂]₃[PV₁₄O₄₂]·2TMP·6H₃O⁺ (2), have been synthesized at different pH values using V₂(SO₄)₃, Ni(CH₃COO)₂, and H₆TTHA (for 1), VO(acac)₂ and TPP (for 2) (en = C₂H₈N₂, TPP = thiamine pyrophosphate, TMP = thiamine monophosphate, H₆TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid). The complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TG), and single crystal X-ray diffraction. The complexes catalyze the oxidation of the organic substrate phenol red in the presence of H₂O₂ and bromide, and the reaction system is considered as a model for hydrogen peroxide determination. The reaction rate constants (k) for 1 and 2 are calculated as 3.729 × 10³ and 4.083 × 10³ (mol L)^?2 s^?1. The maximum conversion rate of phenol red for 1 is 83.32%, while for 2 is 81.12%.     

Synthesis and Characterization of Transition Metal Complexes of Potassium 3‐(Pyridine‐4‐Carbonylmethyl)‐Dithiocarbazate

The preparation and characterization of some dipositive metalion complexes de rived from potassium 3‐(pyridine‐4‐carbonylmethyl)‐dithiocarbazate (PCDHK) are reported. The solid complexes of the composition ML·nH₂O (M=Cu(II), Co(II), Mn(II), Zn(II), Cd(II), Ni(II), Pb(II), L = PCD^?2, n = 0, 1, PCD^?2=PCDHK‐K⁺‐H⁺) and ML₂·2H₂O (M=UO₂(IV), L=PCDH^?1, PCDH^?1=PCDHK‐K⁺) have been characterized by elemental analyses, IR, UV, and ¹HNMR spectra. The IR spectral data indicate that PCDHK be haves as either a mononegative or binegative ligand and coordinates in a tridentate or bridging tetradentate manner.     

Half-sandwich scorpionate nickel complexes with aliphatic dicarboxylic acid co-ligands

A series of new nickel complexes, namely [Tp*Ni(sub)]·EtOH (1), [Tp*Ni(ad)]·EtOH (2), [Tp*Ni(seb)(H₂O)] (3), and [Tp*Ni(μ–suc)NiTp*(MeOH)₂] (4) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate, H₂sub = suberic acid, H₂ad = adipic acid, H₂seb = sebacic acid, H₂suc = succinic acid), were synthesized in mixed solvents at room temperature. The complexes were characterized by physico-chemical and spectroscopic methods. In addition, X-ray crystal structure analysis indicates that the four complexes share a common scorpionate (Tp*) Ni core with different aliphatic dicarboxylic acid ligands, and the nickel atom is in a distorted octahedral environment with the N₃O₃ donor set. Surface voltage spectroscopy indicates that these complexes exhibit surface photovoltage responses in the range of 300–800 nm, which can be assigned to LMCT and d → d ^* electronic transitions. In addition, quantum chemistry calculations on the complexes were performed and are discussed.     

Syntheses and structures of two NiIICoIINiII complexes of macrocyclic ligands

Two new linear trinuclear complexes, [Co(NiL¹)₂(SCN)₂] (1) and [Co(NiL²)₂(H₂O)₂](ClO₄)₂?·?2C₂H₅OH (2), have been prepared by using Co(ClO₄)₂?·?6H₂O and two macrocyclic complex ligands NiL¹ and NiL². L¹ and L² are the doubly deprotonated forms of dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazabicyclo[12.4.0^15,16]13,18-dicarboxylate and dimethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate, respectively. X-ray single crystal analyses reveal the coordination geometries around Ni(II) in both 1 and 2 are identical and slightly distorted square planar with N₄ donors; all Ni–N bonds in the two complexes are very short. The Co(II) ions are at the centers of the trinuclear complexes and have distorted octahedral coordination geometries of O₄N₂ donors in 1 and an O₆ in 2. π?···?π interactions involving aromatic and non-aromatic π-systems join the trinuclear entities to form 2-D layers in the crystals of 1 and 2.     

fac-Cobalt(III)-azido complexes derived from substituted pyridyl-based tridentate amines

Four new mononuclear triazido-cobalt(III) complexes [Co(L ^1/2/4 )(N₃)₃] and [Co(L ³ )(N₃)₃]·CH₃CN where L ¹  = [(2-pyridyl)-2-ethyl]-(2-pyridylmethyl)-N-methylamine, L ²  = [(2-pyridyl)-2-ethyl]-[6-methyl-(2-pyridylmethyl)]-N-methylamine, L ³  = [(2-pyridyl)-2-ethyl]-[3,5-dimethyl-4-methoxy-(2-pyridylmethyl)]-N-methylamine, and L ⁴  = [(2-pyridyl)-2-ethyl]-[3,4-dimethoxy-(2-pyridylmethyl)]-N-methylamine, respectively, were synthesized and structurally characterized. The four complexes were characterized by elemental microanalyses, IR and UV–VIS spectroscopy and X-ray single crystal crystallography. The complexes display two strong IR bands over the frequency region 2,020–2,050 cm^?1 assigned for the asymmetric stretching frequency, ν_a(N₃) of the coordinated azides indicating facial geometry. The molecular structure determinations of the complexes were in complete agreement with fac-[Co(L)(N₃)₃] conformation in distorted octahedral Co(III) environment.