Synthesis and Crystal Structure of a Novel Polymeric Thiocyanato-Bridged Heteronuclear Complex of Copper(II) and Cadmium(II)

The title polymeric complex of Cu(II) and Cd(II) bridged by thiocyanate, Cu(en)₂[Cd(SCN)₃]₂, has been prepared and its structure determined by X-ray diffraction (XRD) methods. The crystal structure reveals that the Cu(II) atom is in an elongated octahedral coordination formed by two SCN^– anions and two en molecules. The Cd(II) atom is in a distorted octahedral coordination formed by six bridging SCN^– anions. Two different bridging thiocyanate anions exist in the complex. Both 1,1--SCN^– and 1,3--SCN^– anion act a role of bridge ligand and link Cu(II), Cd(II) atoms, and adjacent Cd(II). Cd(II) atoms form the three-dimensional (3-D) network polymeric structure. The IR and UV-Vis spectra have also been investigated.     

Synthesis,structure, anticancer activities,and DNA-binding properties of a 1-D polymeric copper(II) complex alternately bridged by oxamide and terephthalate

A 1-D polymeric copper(II) complex alternately bridged by N,N′-bis(N-hydroxyethylaminopropyl)oxamide (heap^2?) and terephthalate (tpa^2?), [Cu₂(heap)(tpa)] _n , has been synthesized and characterized by single-crystal X-ray diffraction. The crystal structure reveals that the asymmetric unit of the copper(II) polymer is half a dinuclear copper(II) complex, [Cu₂(heap)(tpa)], in which Cu(II) is located in a square-pyramidal coordination environment. Separations of Cu(II) through heap^2? and tpa^2? bridges are 5.2459(6) and 11.1375(6)?Å, respectively. The complex chains, accompanied with glide planes parallel to the a0c plane, can be classified to two groups according to their extending direction. Hydrogen bonds occur between a complex chain and any adjacent ones in the other orientation. Consequently, a 3-D supramolecular network is completed. The polymeric copper(II) complex exhibits potent anticancer activities against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549 tested by sulforhodamine B assays. The interactions of the polymeric copper(II) complex with herring sperm DNA (HS-DNA) are investigated by using electronic absorption titration, fluorescence titration, electrochemical titration, and viscometry measurements. The results suggest that the polymeric copper(II) complex interacts with HS-DNA via intercalation with intrinsic binding constant of 1.8?×?10^6?(mol?L^?1)^?1.     

Synthesis,crystal structure and magnetic properties of the first dinuclear copper(II)–iron(II) complex [Cu(L)Fe(CN)5NO] based on nitroprusside

The nitrosyl cyanide [Cu(L)Fe(CN)₅NO] was prepared by the reaction of [Cu(L)]Cl₂ [L = 3, 10-bis(2-hydroxymethyl)-1,3,5,8,10,12-hexaazacyclotetradecane] with Na₂[Fe(CN)₅NO]·2H₂O in aqueous solution. Single-crystal analysis revealed that the title complex is the first structurally characterized dinuclear copper(II)–iron(II) complex based on the nitroprusside. Variable temperature magnetic susceptibility measurements (4.0–180.0 K) show the occurrence of very weak antiferromagnetic interactions between the copper(II) ions with zJ = –0.410 cm^–1.     

Kinetics of oxidation of iron(II) by vanadium(V) under the conditions where VO2+ and decavanadate coexist

The kinetics of the reaction between iron(II) and vanadium(V) have been investigated in the pH range 2.6–4.2 where decavanadates and VO₂⁺ coexist in equilibrium. Under these conditions, the observed kinetic pattern is radically different from the one reported for the reaction in strong acid medium. In the pH range employed, the reaction rate is not appreciably altered by variation in the stoichiometric vanadium(V) concentration due to the operation of the equilibrium between the reactive species, VO₂⁺, and the unreactive species, decavanadates. The reaction, however, obeys first‐order kinetics with respect to Fe(II). In the presence of salicylic acid, which imparts considerable reactivity to iron(II) by reducing the reduction potential of iron(III)/iron(II) couple by forming a stronger complex with iron(III) than iron(II), the kinetic results provide evidence for the participation of decavanadates in the electron transfer. The mechanism under both conditions is discussed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 535–541, 2000     

Synthesis,IR spectrum,thermal property and crystal structure of cyano-bridged heteronuclear polymeric complex, [Cd(teta)Ni(μ-CN)<Subscript>2</Subscript>(CN)<Subscript>2</Subscript>] · 2H<Subscript>2</Subscript>O

The cyano-bridged heteronuclear polymeric complex, [Cd(teta)Ni(μ-CN)₂(CN)₂] · 2H₂O (1), (teta = triethylenetetraamine) was synthesized and characterized by FT-IR spectroscopy, thermal analysis and single crystal X-ray diffraction techniques. It crystallizes in the orthorhombic system, space group Pccn. The asymmetric unit also contains two uncoordinated water molecules. The coordination geometry around the Cd(II) centre is a highly distorted octahedral. In the crystal structure, intramolecular N–H···O and intermolecular N–H···O, O–H···O and O–H···N hydrogen bonds, beside the cyano-bridged chains made up of tetracyanonickelate ions coordinated to Cd(II) ions, where the Ni(II) ion is coordinated by four cyanoligands in a square-planar arrangement, link the molecules into polymeric networks parallel to (001) plane, where the hydrogen bonded water molecules occupy the cavities between the layers. The FT-IR spectrum was reported in the 4,000–400 cm⁻¹ region. Vibration assignments were given for all the observed bands and the spectral feature also supported the structure of the polymeric complex. The decomposition reaction takes place in the temperature range 20–1,000 °C in the static air atmosphere.     

Redox Properties of the Iron Complexes of Orally Active Iron Chelators CP20, CP502, CP509, and ICL670

Redox cycling of iron is a critical aspect of iron toxicity. Reduction of a low‐molecular‐weight iron(III)‐complex followed by oxidation of the iron(II)‐complex by hydrogen peroxide may yield the reactive hydroxyl radical (OH^.) or an oxoiron(IV) species (the Fenton reaction). Complexation of iron by a ligand that shifts the electrode potential of the complex to either to far below ?350 mV (dioxygen/superoxide, pH=7) or to far above +320 mV (H₂O₂/HO^., H₂O pH=7) is essential for limitting Fenton reactivity. The oral chelating agents CP20, CP502, CP509, and ICL670 effectively remove iron from patients suffering from iron overload. We measured the electrode potentials of the iron(III) complexes of these drugs by cyclic voltammetry with a mercury electrode and determined the dependence on concentration, pH, and stoichiometry. The standard electrode potentials measured are ?620 mV, ?600 mV, ?535 mV, and ?535 mV with iron bound to CP20, ICL670, CP502, and CP509, respectively, but, at lower chelator concentrations, electrode potentials are significantly higher.     

A bimetallic cyano-bridged complex based on nickel(II) and pentacyanidonitrosylferrate(II) precursors: characterization, crystal structure, and magnetic properties

A heterobimetallic cyano-bridged 1D coordination polymer of the composition [Ni(baepn)(μ-NC)Fe(CN)₃(NO)(μ-CN)]_n·3H₂O has been synthesized by the reaction of nickel(II) nitrate hexahydrate, baepn (baepn = N, N′-bis(2-aminoethyl)-1,3-propanediamine), and sodium nitroprusside dihydrate in a methanol–water mixture. The complex was characterized by physicochemical and spectroscopic methods. The crystal structure was established by single-crystal X-ray diffraction analysis. It reveals cyano-bridged heterometallic chains consisting of alternating arrays of Ni(II) and Fe(II) atoms, both being embedded in distorted octahedral environments. Low-temperature susceptibility measurements show the presence of weak antiferromagnetic exchange interactions between paramagnetic Ni(II) centers (J = −0.46 cm⁻¹) through long diamagnetic [Fe(CN)₅(NO)]²⁻ bridges. Spin state of the iron atom was established by ⁵⁷Fe M?ssbauer spectroscopy.     

Studies on Cobalt(III) Metallosurfactants. Kinetics and Mechanism of Reduction of Cobalt(III) by Iron(II) in Aqueous Acid Medium

The kinetics and mechanism of reduction of the surfactant complex ions, cis-chloro/bromo(dodecylamine)(triethylenetetramine)cobalt(III) by iron(II) in aqueous solution were studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The second-order rate constant increases with cobalt(III) concentration and the presence of aggregation of the complex itself alters the reaction rate. The reductions are acid-independent in the range [H⁺] = 0.05–0.25 mol dm⁻³. Variation of ionic strength (μ) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe²⁺(aq) with the cobalt(III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependent CMC and the standard Gibbs energy of micellization (ΔG_m⁰).     

Polymeric and monomeric dipicolinate complexes with 4-hydroxymethyl pyridine: spectral, structural, thermal and electrochemical characterization

Polymeric copper(II), [Cu(μ-dpc)(μ-4-hymp)] _n (1), and monomeric nickel(II), [Ni(dpc)(4-hymp)(H₂O)₂]·H₂O (2), (dpc: dipicolinate, 4-hymp: 4-hydroxymethyl pyridine), dipicolinate complexes have been prepared and characterized by spectroscopic (IR, UV–Vis, EPR), thermal (TG/DTA), X-ray diffraction technique and electrochemical methods. In both the dipicolinate complexes, the dpc dianion acts as a tridentate ligand. In polymeric copper(II) complex, the 4-hymp and dpc ligands adopt a bridging position between the Cu(II) centers, forming the elongated octahedral geometry. The polymeric chains are linked to one another via O–H···O hydrogen bond interactions, forming the 3-D polymeric structure. The Ni(II) ion is bonded to dpc ligand through pyridine N atom together with one O atom of each carboxylate group, two aqua ligands and N pyridine atom of 4-hymp, forming the distorted octahedral geometry. The Ni(II) complexes are connected to one another via O–H···O hydrogen bonds, forming R ₄²(18) motifs in 2-D pattern. The powder EPR spectra of copper(II) complex have indicated that the paramagnetic center is in rhombic symmetry with the Cu²⁺ ion having distorted octahedral geometry. IR and UV–Vis spectroscopes all agree with the observed crystal structure.     

Synthesis,spectral, thermal and structural characterization of {[Cu(H2O)3][Cu(MAL)2] · 2H2O}∞ and [Cu(MAL)(TEA)] · H2O (MAL = malonate and TEA = triethanolamine)

A polymeric malonato-bridged copper(II) complex, {[Cu(H₂O)₃][Cu(MAL)₂]· 2H₂O}, and a mononuclear malonato-copper(II) complex with triethanolamine, [Cu(MAL)(TEA)]·H₂O, have been prepared and characterized by elemental analyses, i.r., u.v.–vis, magnetic measurements and single crystal X-ray diffraction. The polymeric complex consists of one-dimensional chains containing the MAL bridged [Cu(H₂O)₃]²⁺ and [Cu(MAL)₂]^2– ions and each MAL ligand simultaneously exhibits chelating bidentate (at one copper atom) and bridging (at the adjacent copper atom) coordination modes. The intrachain Cu1...Cu2 separation is 4.963 Å and the polymeric complex exhibits antiferromagnetic behaviour. In the mononuclear complex, the copper(II) ion is octahedrally coordinated by one bidentate MAL and one tetradentate neutral TEA ligands. The i.r. spectra and thermal decompositions of both complexes are described.     

Formation of polymeric chain assemblies of transition metal complexes with a multidentate Schiff-base

The new multidentate Schiff-base (E)-6,6′-((1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-ylidene))bis(4-methyl-2-((E)(pyridine-2-ylmethylimino)methyl)phenol) H₂L and its polymeric binuclear metal complexes with Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) are reported. The reaction of 2,6-diformyl-4-methyl-phenol with ethylenediamine in mole ratios of 2:1 gave the precursor 3,3′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1ylidene))bis(methan-1-yl-1-ylidene)bis(2-hydroxy-5-methylbenzaldehyde) W. Condensation of the precursor with 2-(amino-methyl)pyridine in mole ratios of 1:2 gave the new N₆O₂ multidentate Schiff-base ligand H₂L. Upon complex formation, the ligand behaves as a dibasic octadentate species with the involvement of the nitrogen atoms of the pyridine groups in coordination for all complexes. The mode of bonding and overall geometry of the complexes were determined through physico-chemical and spectroscopic methods. These studies revealed octahedral geometries for Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Cd(II) and Hg(II) complexes of general formulae [Cr₂^III(L)Cl₂]Cl₂, [Ni₂^II(L)(H₂O)₂]Cl₂ and [M₂(L)Cl₂] and five co-ordinate Zn(II) complex of general formula [Zn₂^II(L)]Cl₂.     

Crystal structure and magnetic properties of a new polymer [Cu(PzdcH)2·2H2O]n

Two different products are obtained when 2,3-pyrazinedicarboxylic acid (PzdcH₂) reacts separately with two copper(II) salts: Cu(OAc)₂ and CuCl₂. One product is a mononuclear Cu^II complex Cu(PzdcH)₂·2H₂O, the other is a linear polymeric copper(II) complex [Cu(PzdcH)₂·2H₂O]_n, whose structure has been determined by X-ray diffraction at room temperature. The polymeric complex is composed of copper(II) ions, PzdcH^- anions and crystal water molecules. The Cu(1) atom is located in elongated octahedral coordination environment with six donor atoms: O(1), N(1), O(1a), N(1a), O(3b) and O(3c) from four different PzdcH^- anions. The two oxygen atoms O(3b) and O(3c) come from the carboxylic acid group of the PzdcH^- anion of the upper and lower layers, so that an infinite chain constitutes the crystal lattice. There are very strong hydrogen bond interactions between chains which lead to a three-dimensional structure. The magnetic susceptibility of the polymeric complex [Cu(PzdcH)₂·2H₂O]_n has been determined in the 1.5–300K range. A study of magnetic properties shows that a weak antiferromagnetic interaction exists between two copper(II) ions.     

Synthesis and Crystal Structure of a Polymeric Heteronuclear Complex of Cadmium(II) and Silver(I)

A polymeric complex of Cd(II) and Ag(I) bridged by thiocyanate and ethylenediamine, [Cd(en)_1.5Ag(SCN)₃], has been prepared and its structure determined by X-ray diffraction methods. The complex crystallizes in space group P2₁/n with a =7.456(1), b =9.915(2), c =19.822(2)Å, β =98.94(1)°. The Cd(II) atom is octahedrally coordinated by three SCN^- anions and two en molecules, while the Ag(I) atom is tetrahedraly coordinated by four SCN^- anions. Both SCN^- anions and en molecules act as bridging ligands and link Ag(I) and Cd(II) atoms to form a three-dimensional polymeric structure. The distance between Ag(I) and the atom S of a 1,1,3-µ3-SCN^- anion is much longer than that between Ag(I) and the atom S of a 1,3-µ-SCN^- anion. The short Ag-Ag distance of 3.133 Å and small Ag-S-Ag angle of 70.92° strongly suggests the existence of an Ag-Ag bonding interaction in the complex.     

Halido-bridged Copper(II) Complexes with 1-tert-Butyl-1H-tetrazole: Crystal Structure and Magnetic Properties

Complex [Cu(tbt)Cl₂]_n (tbt = 1-tert-butyl-1H-tetrazole) was prepared by reaction of tbt with copper(II) chloride in solution. According to single-crystal X-ray analysis, this complex presents 1D coordination polymer, formed at the expense of double chlorido bridges between neighboring pentacoordinate copper(II) cations. 1-tert-Butyl-1H-tetrazole acts as monodentate ligand coordinated by Cu^II cations via the heteroring N⁴ atoms. The temperature-dependent magnetic susceptibility measurements of novel complex [Cu(tbt)Cl₂]_n as well as described previously 1D coordination polymer [Cu(tbt)₂Cl₂]_n, and linear trinuclear complex [Cu₃(tbt)₆Br₆], were carried out. Magnetic studies revealed that the copper(II) ions were weakly ferromagnetically coupled in polymeric copper(II) chloride complexes, whereas complex [Cu₃(tbt)₆Br₆] showed antiferromagnetic coupling.     

Dioxygen Reactivity of Biomimetic Iron–Catecholate and Iron–o‐Aminophenolate Complexes of a Tris(2‐pyridylthio)methanido Ligand: Aromatic C?C Bond Cleavage of Catecholate versus o‐Iminobenzosemiquinonate Radical Formation

An iron(III)–catecholate complex [L¹Fe^III(DBC)] ( 2 ) and an iron(II)–o‐aminophenolate complex [L¹Fe^II(HAP)] ( 3 ; where L¹=tris(2‐pyridylthio)methanido anion, DBC=dianionic 3,5‐di‐tert‐butylcatecholate, and HAP=monoanionic 4,6‐di‐tert‐butyl‐2‐aminophenolate) have been synthesised from an iron(II)–acetonitrile complex [L¹Fe^II(CH₃CN)₂](ClO₄) ( 1 ). Complex 2 reacts with dioxygen to oxidatively cleave the aromatic C? C bond of DBC giving rise to selective extradiol cleavage products. Controlled chemical or electrochemical oxidation of 2 , on the other hand, forms an iron(III)–semiquinone radical complex [L¹Fe^III(SQ)](PF₆) ( 2^ox‐PF₆ ; SQ=3,5‐di‐tert‐butylsemiquinonate). The iron(II)–o‐aminophenolate complex ( 3 ) reacts with dioxygen to afford an iron(III)–o‐iminosemiquinonato radical complex [L¹Fe^III(ISQ)](ClO₄) ( 3^ox‐ClO₄ ; ISQ=4,6‐di‐tert‐butyl‐o‐iminobenzosemiquinonato radical) via an iron(III)–o‐amidophenolate intermediate species. Structural characterisations of 1 , 2 , 2^ox and 3^ox reveal the presence of a strong iron? carbon bonding interaction in all the complexes. The bond parameters of 2^ox and 3^ox clearly establish the radical nature of catecholate‐ and o‐aminophenolate‐derived ligand, respectively. The effect of iron? carbon bonding interaction on the dioxygen reactivity of biomimetic iron–catecholate and iron–o‐aminophenolate complexes is discussed.     

Solid state kinetics of Cu(II) complex of [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] from thermo gravimetric analysis

The ligand [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] (L) is a schiff base derived from condensation reaction of 1,2,3,4-thiatriazole-5-ylamine and Salicylaldehyde. Synthesis of the ligand (L) and the complex [Cu(II)(L)₂]·2H₂O have been studied in our previous work (Bharti et al., Asian J Chem 23(2):773–776, 2011). Thermal decomposition behavior of synthesized Cu(II) complex has been investigated by thermo gravimetric (TG) analysis at heating rate of 10 °C min⁻¹ under nitrogen atmosphere. The mechanism of decomposition of Cu(II) complex has been established from TG data. Kinetic parameters such as order of reaction (n), activation energy (E _a), frequency factor (Z) and entropy of activation (∆S ^≠) were calculated by using Freeman and Carroll (J Phys Chem 62:394–397, 1958) as well as Doyle’s methods as modified by Zsako (J Phys Chem 72(7):2406–2411, 1968).     

Studies on the Reaction Kinetics and Mechanism of Iron(II) Reduction of the <Emphasis Type="Italic">cis</Emphasis>-Halogeno(cetylamine)bis(ethylenediamine)cobalt(III) Complex Ion in Aqueous Perchlorate Medium

The electron-transfer kinetics of the ionic surfactant complex cis-chloro/bromo(cetylamine)bis(ethylenediamine)cobalt(III) by iron(II) in aqueous perchlorate medium at μ=1.0 mol⋅dm⁻³ ionic strength have been studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The effects of [H⁺], ionic strength and [Fe²⁺] on the rate were determined. The reaction was found to be second order and showed to be independence of the acid concentration in the range [H⁺]=0.05–0.25 mol⋅dm⁻³. The second order rate constant increased with surfactant–cobalt(III) concentration and the occurrence of aggregation of the complex itself altered the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe²⁺(aq) with the cobal (III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant–metal complexes were obtained in aqueous solution from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependence of the critical micelle concentration (CMC) and the thermodynamics of micellization (ΔG _m^o,ΔH _m^o and ΔS _m^o).     

The anion-directed self-assembly of manganese complexes derived from 2-ethoxy-6-[(2-phenylaminoethylimino)methyl]phenol

The mixed valence manganese(II/IV) complex, [Mn^IIL₂(MeOH)₂]·[Mn^IVL₂(OAc)₂]·2(MeOH) (1), and the chloride-bridged 1D polymeric manganese(III) complex, [Mn^IIIL₂(μ-Cl)]_n (2), where L is the deprotonated form of 2-ethoxy-6-[(2-phenylaminoethylimino)methyl]phenol (HL), have been prepared and structurally characterized by single-crystal X-ray diffraction analysis and IR spectra. The Mn atoms in both complexes are octahedrally coordinated. The self-assembly of the complex structures is apparently directed by the anions of the manganese salts.     

Structural elucidation of manganese(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of a new multidentate dihydrazino quinoxaline derivative

Summary Manganese(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of a new multidentate oxygen-nitrogen donor, bis(N-salicylidene)-2,3-dihydrazino-1,4-quinoxaline (H₂BSDHQ) were prepared and characterised by elemental analysis, conductance, thermal, spectral and magnetic data. H₂BSDHQ deprotonates to give a dibasic ONNO donor set in a trivalent iron(III) complex, which binds to the divalent metal ions in a bis-tridentate fashion, using two monobasic ONN donor sets, and resulting in polymeric complexes. Octahedral geometries are proposed for all these complexes, and preliminary studies show that they possess potential antimicrobial activity.     

Copper(II)–1,2-bis(thiocarbamoyl)hydrazine and copper(II)–(1-carbamoyl-2-thiocarbamoyl)hydrazine complexing in copper(II)hexacyanoferrate(II) gelatin-immobilized matrix systems

The complex formation that occurs in gelatin-immobilized copper(II)hexacyanoferrate(II) matrices upon contact with aqueous alkaline (pH 12.0) solutions of 1,2-bis(thiocarbamoyl)hydrazine, H₂NC(S)NHNHC(S)NH₂ and 1-carbamoyl-2-(thiocarbamoyl)hydrazine, H₂NC(O)NHNHC(S)NH₂ has been studied. The reaction of each of these ligands with copper(II) is preceded by the destruction of copper(II)hexacyanoferrate(II) in an alkaline medium to form a polymeric copper(II) hydroxide, which is involved in the subsequent copper(II)–ligand complex formation. In both Cu^II–N ligand systems, two complex compounds are formed; the water-insoluble Cu₂B₂(H₂O)₂ dimer and a water-soluble product of tentative composition [CuB(HB)]^– (H₂B=ligand).