Synthesis of unsymmetrical compartmental oxime nickel(II) and copper(II) complexes: spectral, electrochemical and magnetic studies

A new series of binuclear unsymmetrical compartmental oxime complexes (1–5) [M₂L] [M=Cu(II), Ni(II)] have been synthesized using mononuclear complex [ML] (L=1,4-bis[2-hydroxy-3-(formyl)-5-methylbenzyl]piperazine), hydroxylamine hydrochloride and triethylamine. In this system there are two different compartments, one has piperazinyl nitrogens and phenolic oxygens and the other compartment has two oxime nitrogens and phenolic oxygens as coordinating sites. The complexes were characterized by elemental and spectral analysis. Electrochemical studies of the complexes show two step single electron quasi-reversible redox processes at cathodic potential region. For copper complexes E¹ _pc=−0.18 to −0.62 and E² _pc=−1.18 to −1.25 V, for nickel complexes E¹ _pc=−0.40 to −0.63 and E² _pc=−1.08 to −1.10 V and reduction potentials are sensitive towards the chemical environment around the copper and nickel atoms. The nickel(II) complexes undergo two electrons oxidation. The first one electron oxidation is observed around +0.75 V and the second around +1.13 V. ESR Spectra of the binuclear copper(II) complexes [Cu₂L](ClO₄), [Cu₂L(Cl)], [Cu₂L(NO₃)] shows a broad signal at g=2.1 indicating the presence of coupling between the two copper centers. Copper(II) complexes show a magnetic moment value of μ_eff around 1.59 B.M at 298 K and variable temperature magnetic measurements show a −2J value of 172 cm⁻¹ indicating presence of antiferromagnetic exchange interaction between copper(II) centres.     

Electronic, EPR, magnetic and mass spectral studies of mono and homo-binuclear Co(II) and Cu(II) complexes with a novel macrocyclic ligand

A series of 20-memebered macro-cyclic metal(II) complexes have been synthesized by a macro-cyclic ligand, i.e. 1,5,11,15-tetraaza-6,10,16,20-tetraoxo-8,18-dithia-cyclocosane, it was prepared by the condensation reaction of 1,3-diaminopropane with thiodiglycolic acid. The bonding and stereochemistry of the complexes have been characterized by elemental analysis, magnetic moment, molar conductance, mass, 1H NMR, IR, electronic and EPR spectral studies. The mononuclear complexes of the type [ML]X2 have been found to have distorted octahedral geometry and the binuclear complexes [M2LX2]X2 were found to possess square planar configuration around the central metal ion.     

Synthesis,spectral, and catalytic studies of ruthenium(II) unsymmetrical Schiff-base complexes

Unsymmetrically-substituted ruthenium(II) Schiff-base complexes, [Ru(CO)(B)(L ^x )] [B = PPh₃, AsPh₃ or Py; L ^x = dianion of tetradentate unsymmetrical Schiff-base ligand; x = 4–7, L⁴ = salen-o-hyac, L⁵ = valen-o-hyac, L⁶ = salphen-o-hyac, L⁷ = valen-2-hacn], were prepared and characterized by analytical, IR, electronic, and ¹H NMR spectral studies. The new complexes were tested for their catalytic activity towards the oxidation of benzylalcohol to benzaldehyde.     

Thermal,spectral and magnetic studies on glycine complexes of cobalt(II), nickel(II) and zinc(II) with hydrazine

Hydrazinium metal glycinates [(N₂H_{5 2}M(NH₂CH₂COO)₄] and bis(hydrazine)metal glycinates, [M(NH₂CH₂COO)₂(N₂H₄)₂], whereM=Co, Ni or Zn have been prepared and characterized by chemical analyses, magnetic moments and vibrational and electronic spectra. The thermal behaviour of these compounds has been studied by thermogravimetry and differential thermal analyses. These complexes decompose with high exothermicity giving metal powder as the final residue. The X-ray powder data of each set of complexes show isomorphism among themselves.     

Spectral,magnetic, thermal and electrochemical studies on new copper(II) thiosemicarbazone complexes

The chelation behavior of some =N(1) and NH(4) thiosemicarbazones towards copper(II) ions has been investigated. The isolated complexes are characterized by elemental analysis, magnetic moment, electronic, IR, ESR and ms spectra, and by thermal and voltammetric measurements. The substituents on =N(1) and/or NH(4) thiosemicarbazones and the log K values of the ligands play an important role in complex formation. The IR spectra showed that the reagents HAT, HAET, HAPT, HApClPT, H₂ST and HBT are deprotonated in the complexes and act as mononegative SN donors; H₂SET, H₂SpClPT, H₂HyMBPT and H₂HyMBpClPT, as binegative NSO donors while H₂SPT is a mononegative NSO donor. The ESR spectra of the complexes are quite similar and exhibit axially symmetric g-tensor parameters with g _‖?>?g _⊥?>?2.0023. The loss of thiol and/or hydroxyl hydrogen was confirmed from potentiometric titrations of the ligands and their copper(II) complexes. The protonation constants of the ligands as well as the stability constants of their Cu(II) complexes were calculated. Thermogravimetric analysis of the complexes suggests different decomposition steps. The Coats–Redfern and Horowitz–Metzger equations have been used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The redox properties, nature of the electroactive species and the stability of the complexes towards oxidation are strongly dependent on the substituents on the precursor NH(4) thiosemicarbazone. The redox data are discussed in terms of the kinetic parameters and the reaction mechanism.     

Chromotropism studies on copper(II) compounds. Part II. Dinuclear copper(II) complexes with triply-bridged hydroxo,acetate, and halo ligands

Abstract

Two triply-bridged dinuclear copper(II) complexes of formula [LCu(μ-OH)(μ-OAc)(μ-X)CuL]X?0.5H₂O where L is a bidentate ligand of N-(pyridine-2-ylmethyl)propane-2-amine and X=Cl, 1 and Br, 2 were synthesized and characterized by elemental analyses, spectroscopic techniques (IR, UV–Vis, EPR), thermal analysis, conductance measurements, and single-crystal X-ray structure determination. The structures of both complexes are similar. The complexes show a distorted square-pyramidal arrangement around each copper(II) ion with a CuN₂O₂X chromophore in which both copper(II) ions are connected by a hydroxo bridge and a triatomic syn-syn carboxylato bridge in equatorial positions and a halide ion bridge at the axial site. The chromotropism behavior of the complexes, including solvato-, thermo-, and halochromism, were investigated in detail. Their halochromism was investigated in the pH range of 2.0–11.0 by visible absorption spectroscopy. The reversible color variations from blue to colorless are attributable to deprotonation and protonation of the ligands. The complexes show reversible thermochromism in solution due to dissociation and recombination of ligands to copper ions.     

Thermal stability study of some azo-derivatives and their complexes,Part 2. New azo-derivative pigments and their Cu(II) complexes

This paper deals with the investigation concerning the thermal stability of two new azo-derivatives and their Cu(II) complexes of type [Cu(L¹)₂] and, respectively, ((C₄H₉)₄N)₂[Cu(L²)₂]. The thermal decomposition steps have been put in evidence. For the kinetically workable ones, the values of the activation energy vs. conversion degree were determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis,spectral characterization,anticancer and antibacterial studies of cyclodiphosph(V)azane derivatives and their copper(II) complexes

The new cyclodiphosph(V)azane derivatives (1,3-dimethyl-2,4-dioxo-2',4'-bis(2,4-bis(dimethylaminopropylimino)cyclodiphosph(V)azane (H₂L¹) (1,3-dimethyl-2,4-dioxo-2',4'-bis(2,4-bis(dimethylaminoethylimino)cyclodiphosph(V)azane (H₂L²) and (1,3-dimethyl-2,4-dioxo-2'-(dimethylaminoethylimino)-4'-(dimethylaminopropyl-imino)cyclodiphosph(V)azane (H₂L³) containing four active coordination centers (NNNN) and their Cu(II) complexes have been synthesized and characterized by elemental analyses, spectroscopic methods, molar conductance as well as thermal and magnetic measurements. The UV–Vis and mass spectra of the ligands and their Cu(II) complexes were also recorded. The copper(II) complexes were found to have magnetic moments of 1.58–1.69 B. M. corresponding to one unpaired electron. The possible geometries of the complexes were assigned on the basis of EPR, electronic, and infrared spectral studies. The absence of water molecules in all complexes was supported by thermal studies. All the thermal decomposition processes ended with the formation of CuO. The kinetic and thermodynamic parameters have been calculated. The ligand (H₂L³) and its Cu(II) complexes were screened for their anticancer studies against human breast cancer cell lines MCF-7 and minimum inhibitory concentration was calculated. The screening was extended to the antibacterial activity using Kirby–Bauer single disk susceptibility test for all compounds.     

Synthesis,spectral characterization and biological studies of transition metal(II) complexes with triazole Schiff bases

New metal based triazoles (1–12) have been synthesized by the interaction of novel Schiff base ligands (L¹–L³) with the Co(II), Ni(II), Cu(II) and Zn(II) metal ions. The Schiff base ligands and their all metal(II) complexes have been thoroughly characterized using various physical, analytical and spectroscopic techniques. In vitro bacterial and fungal inhibition studies were carried out to examine the antibacterial and antifungal profile of the Schiff bases in comparison to their metal(II) complexes against two Gram‐positive, four Gram‐negative and six fungal strains. The bioactivity data showed the metal(II) complexes to have more potent antibacterial and antifungal activity than their uncomplexed parent Schiff bases against one or more bacterial and fungal species. Copyright © 2012 John Wiley & Sons, Ltd.     

EPR, IR and electronic spectral studies on Ni(II) and Cu(II) complexes with N-donor tetradentate [N4] macrocyclic ligand

Nickel(II) and copper(II) complexes are synthesized with a novel tetradentate macrocyclic ligand, i.e. 2,6,12,16,21,22-hexaaza;3,5,13,15-tetraphenyltricyclo[15,3,1,1(7-11)] docosa;1(21),2,5,7,9,11(22),12,15,17,19-decaene (L) and characterized by the elemental analysis, magnetic susceptibility measurements, mass, (1)H NMR, IR, electronic and EPR spectral studies. All the complexes are non-electrolytic in nature. Thus, these may be formulated as [M(L)X(2)] [M=Ni(II), Cu(II) and X=Cl(-), NO(3)(-) and (1/2)SO(4)(2-)]. Ni(II) and Cu(II) complexes show magnetic moments corresponding to two and one unpaired electron, respectively. On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Ni(II) and tetragonal geometry for Cu(II) complexes.     

Synthesis,spectral, structural,and DFT studies on nickel(II) complexes with pyrrole based dithiocarbamate and triphenylphosphine ligands

Bis(N-(pyrrol-2-ylmethyl)-N-isopropyldithiocarbamato-S,S′)nickel(II) (1) and (N-(pyrrol-2-ylmethyl)-N-isopropyldithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II) (2) have been prepared and characterized by elemental analysis, IR, ¹H, and¹³C NMR and UV-visible absorption spectra. In addition, the structures of 2 and (N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II) (3) have been elucidated by X-ray crystallography. UV-vis spectral data are consistent with the formation of square planar complexes. The crystal structures of 2 and 3 reveal S₂NP square-planar configuration around the Ni atom. A rare C–H···Ni short contact interaction was observed in complex 3 involving ortho-hydrogen atom of one of the phenyl ring of the triphenylphosphine. DFT calculations on complexes 2 and 3are in close agreement with the crystallographic results. The energy gap between HOMO and LUMO for 2 and 3 is 2.7167 and 2.6936 eV, respectively. Molecular electrostatic potential analysis of 2 and 3 support the partial double character of thioureide C–N bond.     

Synthesis, structure, and magnetic properties of two 1-D helical coordination polymeric Cu(II) complexes

Two helical coordination polymeric copper(II) complexes bearing amino acid Schiff bases HL or HL′, which are condensed from 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid or l-valine, respectively, have been prepared and characterised by X-ray crystallography. In [CuL]_n (1) the copper(II) atoms are bridged by syn-anti carboxylate groups giving infinite 1-D right-handed helical chains which are further connected by weak C-H?Cu interactions to build a 2-D network. While in [CuL′]_n (2) the carboxylate group acts as a rare monatomic bridge to connect the adjacent copper(II) atoms leading to the formation of a left-handed helical chain. Magnetic susceptibility measurements indicate that 1 exhibits weak ferromagnetic interactions whereas an antiferromagnetic coupling is established for 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data.     

Photochemistry of macromolecular metal complexes. II. Synthesis,thermal, and photochemistry of some polypyridyl complexes of chromium (III) bound to macromolecules

Polymer coordinated chromium(III) complexes [Cr(bpy)₂(PAA)₂]⁺, 1 , [Cr(bpy)₂-(PMA)₂]⁺, 2 , [Cr(phen)₂(PAA)₂]⁺, 3 , and [Cr(phen)₂(PMA)₂]⁺, 4 , [where bpy, phen, PAA and PMA are, respectively, 2,2′-bipyridine, 1,10-phenanthroline, poly(acrylic acid), and poly(methacrylic acid)] were synthesized. The polymer–chromium(III) complexes were characterized by elemental and spectroscopic analyses. Thermal substitution reactions of these macromolecular chromium(III) complexes in basic solutions lead to the replacement of the polypyridyl ligand by hydroxide ion while in strong acidic solutions the polymer complexes precipitate out. The photochemical reactions are qualitatively similar to that of the thermal reactions and the quantum yields are dependant on the pH of the medium. Further, lower quantum yields were observed for the aquation of the polymer complexes in comparison with the monomeric chromium(III) complexes and the results are discussed in terms of the effect of the polymer environment. Flash photolysis of 1 and 3 results in the formation of transients with maxima at 480 nm for 1 and 470 nm, 580 nm for 3 . The decay of the transients were found to obey first order kinetics and the rate constants were determined. The transients were suggested to be the alkyl-chromium complexes. Flash photolysis of 2 and 4 does not produce transients which is interpreted to be due to the presence of a methyl group in the ligand which hinders the formation of the carbonchromium bond.     

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.     

Synthesis, spectral and structural studies of 1-ethoxycarbonyl-piperazine-4-carbodithioate and its Co(III), Zn(II) and Cd(II) complexes

The new complexes [Co(ecpzdtc)₃] (2) [Zn(ecpzdtc)₂(py)] (3) and [Cd(ecpzdtc)₂(py)]·H₂O (4) have been synthesized from sodium 1-ethoxycarbonyl-piperazine-4-carbodithioate [(Na⁺(ecpzdtc)⁻]. The ligand and the complexes have been characterized by elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. The [Zn(ecpzdtc)₂(py)] and [Cd(ecpzdtc)₂(py)]·H₂O complexes contain pyridine as the co-ligand. [Co(ecpzdtc)₃] (2) crystallizes in the monoclinic system, whereas [Zn(ecpzdtc)₂(py)] (3) and [Cd(ecpzdtc)₂(py)]·H₂O (4) crystallize in the triclinic system. The sulfur donor sites of the bidentate ligand chelate the metal center, forming a four-membered CS₂M ring. The cobalt complex has a distorted octahedral geometry, the zinc complex is almost between trigonal bipyramidal and square pyramidal, whereas the cadmium complex is square pyramidal. The crystal structures of all the complexes are stabilized by various types of inter and intramolecular hydrogen bonding.     

Synthesis, electronic and ESR spectral studies on copper(II) nitrate complexes with some acylhydrazines and hydrazones

This paper describes the preparation of [Cu(bh)(2)(H(2)O)(2)](NO(3))(2)], [Cu(ibh)(2)(NO(3))(2)], [Cu(ibh)(2)(H(2)O)(2)](NO(3))(2) and [Cu(iinh)(2)(NO(3))(2)] (bh=benzoyl hydrazine (C(6)H(5)CONHNH(2)); ibh=isonicotinoyl hydrazine (NC(5)H(4)CONHNH(2)); ibh=isopropanone benzoyl hydrazone (C(6)H(5)CONHN=C(CH(3))(2); iinh=isopropanone isonicotinoyl hydrazone (NC(5)H(4)CONHN=C(CH(3))(2)). These copper(II) complexes are characterized by elemental analyses, molar conductances, dehydration studies, ESR, IR and electronic spectral studies. The electronic and ESR spectra indicate that each complex exhibits a six-coordinate tetragonally distorted octahedral geometry in the solid state and in DMSO solution. The ESR spectra of most of the complexes are typically isotropic type at room temperature (300K) in solid state as well as in DMSO solution. However, all the complexes exhibit invariably axial signals at 77K in DMSO solution. The trend g(||)>g( perpendicular)>g(e,) observed in all the complexes suggests the presence of an unpaired electron in the [Formula: see text] orbital of the Cu(II). The bh and inh ligands bond to Cu(II) through the >CO and NH(2) groups whereas, ibh and iinh bond through >CO and >CN groups. The IR spectra of bh and ibh complexes also show HOH stretching and bending modes of coordinated water.     

Six coordinate Ni(II) complexes of ONN donor aroylhydrazone ligands: synthesis,spectral studies,and crystal structures

A new ligand N′-(pyridin-2-ylmethylene)nicotinohydrazide (HL²) and two Ni(II) complexes of stoichiometry NiL¹·H₂O [L¹-2-benzoylpyridine nicotinoylhydrazone] and NiL²·H₂O have been synthesized and characterized by elemental analyses, IR and UV–Vis spectral studies. Structures of HL² and Ni(II) compounds have been determined by single crystal X-ray diffraction studies which reveal a distorted octahedral geometry around the two Ni(II) centers.

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Graphical abstract A new ligand N￠-(pyridin-2-ylmethylene)nicotinohydrazide (HL2) and two Ni(II) complexes of stoichiometry NiL1·H2O [L1-2-benzoylpyridine nicotinoylhydrazone] and NiL2·H2O have been synthesized and characterized by elemental analyses, IR, UV–Vis spectral studies and single crystal X-ray analysis.

     

Synthesis,structure and spectral studies on mixed ligand copper(II) complexes of diimines and acetylacetonate

Two new mixed ligand complexes of copper(II) with acetylacetonate (acac), 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) belonging to the class of cytotoxic and antineoplastic compounds known as CASIOPEINAS^® were synthesized and structurally characterized. Crystals of both complexes [Cu(acac)(bpy)(H₂O)]NO₃ · H₂O (1), [Cu(acac)(phen)Br] (2) contain square pyramidal Cu(II) complex species. In frozen solution both compounds give well resolved EPR spectra with very similar parameters.