Coordination Of CuII Research Articles

Identification of Binding Sites in Copper(II)-Peptide Complexes Using Infrared Spectroscopy.

Complex formation of the copper(II) ion (CuII) with histidine (H) and H-containing peptides plays a crucial role in various metallo-enzymatic reactions. To elucidate the nature of coordinate bonding in CuII complexes, Fourier-transform infrared spectroscopy and 2D IR spectroscopy were employed to investigate the coordination geometries of CuII with diglycine, l-histidylglycine (HG), glycyl-l-histidine (GH), and glycylglycyl-l-histidine. The coordination of CuII to different peptide groups, including the peptide N- and C-termini, the amide group, and the imidazole of the H side chain, exhibits distinct spectral features. The derived molecular structure of the CuII-HG complex based on these spectral features significantly differs from that of CuII-GH, suggesting a preference of the N-terminus and the steric hindrance of the H side chain in CuII chelation.

A New Family of 2D Coordination Polymers Based on 3d‐4f 15‐Metallacrown‐5 Units: Synthesis, Structure, and Single‐Molecule Magnet Behavior

A new family of 2D coordination polymers based on 3d‐4f 15‐metallacrown‐5 (MC) units were designed and characterized. The connection of the 15‐metallacrown‐5 subunits by the coordination of CuII and ligand led to the formation of 2D network of metallacrowns. Analysis of the magnetic properties of these coordination polymers reveals that the GdIII (1), TbIII (2), and DyIII (3) complexes exhibit slow magnetic relaxation and under 1000 Oe dc field, and the DyIII (3) complex exhibits single‐molecule magnet behavior.

A CuII complex with an carbamoylcyanonitrosomethanide ligand formed in situ by the nucleophilic addition of water to dicyanonitrosomethanide: structure, spectral and magnetic properties.

The complex (2,2'-biquinoline-κ2N,N')(carbamoylcyanonitrosomethanide-κ2N,O)chloridocopper(II) acetonitrile monosolvate, [Cu(C3H2N3O2)Cl(C18H12N2)]·CH3CN or [Cu(ccnm)Cl(biq)]·acn (acn is acetonitrile, biq is 2,2'-biquinoline and ccnm is carbamoylcyanonitrosomethanide), (I), was prepared as a result of nucleophilic addition of water to the dicyanonitrosomethanide ion in the presence of CuII and biq. IR spectroscopy confirmed the presence of ccnm, biq and acn in (I). The solid-state structure consists of the neutral complex containing ccnm and biq ligands, coordinated to the CuII atom in a bidendate chelating manner, and a chloride ligand, resulting in a distorted tetragonal pyramidal coordination of CuII. The asymmetric unit is supplemented by one molecule of solvated acn which, along with the nitrile group of ccnm, serves as an acceptor in intermolecular hydrogen bonding, creating infinite chains along the b axis. Magnetic measurements revealed a paramagnetic behaviour with a very small Weiss temperature Θ= -0.32 K and high anisotropy of the g tensor (gx = 2.036, gy = 2.120 and gz = 2.205).

Design of Zn-, Cu-, and Fe-Coordination Complexes Confined in a Self-Assembled Nanocage.

The encapsulation of coordination complexes in a tetragonal prismatic nanocage (1·(BArF)8) built from Zn-porphyrin and macrocyclic Pd-clip-based synthons is described. The functional duality of the guest ligand L1 allows for its encapsulation inside the cage 1·(BArF)8, along with the simultaneous coordination of ZnII, CuII, or FeIII metal ions. Remarkably, the coordination chemistry inside the host-guest adduct L1⊂1·(BArF)8 occurs in both solution solution and solid state. The resulting confined metallocomplexes have been characterized by means of UV-vis, ESI-HRMS, NMR, and EPR techniques. Furthermore, the emission of the Zn-porphyrin fluorophores of 1·(BArF)8 is strongly quenched by the encapsulation of paramagnetic complexes, representing a remarkable example of guest-dependent tuning of the host fluorescence.

Neo‐Fused Hexaphyrin: A Molecular Puzzle Containing an N‐Linked Pentaphyrin

AbstractThe first neo‐confused hexaphyrin(1.1.1.1.1.0) was synthesized by oxidative ring closure of a hexapyrrane bearing two terminal “confused” pyrroles. The new compound displays a folded conformation with a short interpyrrolic C⋅⋅⋅N distance of 3.102 Å, and thus it readily underwent ring fusion to afford a neo‐fused hexaphyrin with an unprecedented 5,5,5,7‐tetracyclic ring structure. Furthermore, coordination of CuII triggered a ring opening/contracting reaction to afford a CuII complex of an N‐linked pentaphyrin derivative. The roles of reactive NC bonds in the porphyrinoid macrocycles were demonstrated.

Dinuclear heme and non-heme metal complexes as bioinspired catalysts for oxidation reactions

Inspired by catalytic sites of cytochrome c oxidase (CcO) and nitric oxide reductase (NOR), a new series of dinuclear heme–non-heme complexes is described. The complexes are derived from the association between an iron(III)–protoporphyrin IX containing a covalently attached Gly-L-His-OMe residue to one propionic acid substituent (HMGH) and a metal complex with a tridentate amino-bis(benzimidazole) (BBH) ligand, mimicking the tris-histidine coordination of FeB and CuB in NOR and CcO, respectively. Besides the coordination of FeIII and CuII with the BBH ligand, we also explored the role of “non-biomimetic” metals, such as CoII, MnII, or ZnII, in order to establish the priority among the ancillary metal ions in cooperating with the ferric heme and promoting its catalytic activity in oxidation reactions. pH-spectrophotometric titrations show that the presence of the non-heme metal decreases the pKa of water-bound to hemin (pKa = 8.4 ± 0.1), with a larger effect with iron(III), copper(II) and zinc(II) complexes (pKa of 6.4 ± 0.1, 6.0 ± 0.1 and 6.5 ± 0.1, respectively), which suggests that an interaction with the non-heme metal center takes place also at a micromolar range. NMR spectra indicate that the interaction between hemin and the non-heme center is not strong enough to convert the high spin configuration of FeIII–heme to low spin as observed for CcO and NOR enzymes. The dinuclear complex enhances the peroxidase-like activity of heme in kinetic studies performed at pH 5.5, 7.0 (using 3-(4-hydroxyphenyl)-propanoic acid as the substrate) and 9.0 (using o-phenylenediamine). In particular, the stronger effects are observed with FeIII, CuII, and CoII complexes, which increase the turnover rates of hemin throughout the pH range analyzed. At neutral and basic pH the KM value decreases up to one fourth indicating a positive cooperation between HMGH and [M(BBH)]n+ in binding the substrates. Moreover, the presence of the non-heme center facilitates the binding of H2O2 and formation of high valent ˙PFeIVO species. These data show that interaction between the two metal centers occurs with heme in several oxidation states.

Synthesis of zwitterionic polymer by SET-LRP at room temperature in aqueous

The Cu0-mediated single electron transfer-living radical polymerization of acrylamide and N,N-dimethyl-N-methacryloyloxyethyl-N-sulfobutyl ammonium in aqueous at 25 °C using 2-chloropropionamide as initiator with Cu0 powder/tris-(2-dimethylamino ethyl)amine (Me6-TREN) as catalyst system is studied. The results showed the characteristic of the “living” polymerization that were the Mn of polymers increased linearly with monomer conversion and the ln([M]0/[M]) increased linearly with time too, meanwhile the narrow molecular of weight distributions were found at most cases. Because of the high rate constant of propagation and bimolecular termination of the acrylamide, the external addition of CuCl2 is required to mediate deactivation the early stage of polymerization. In addition, the disproportionation constant of CuIX/L in H2O is higher than in other solvents and the coordination of amino group and CuII takes place easily, so the isopropanol or N,N-dimethylformamide is added to control the polymerization. High conversions were achieved within short time and the polymers prepared showed good antipolyelectrolyte properties in inorganic salts solutions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Chloridotetrakis(imidazole)copper(II) chloride

The title compound, [CuCl(C3H3N2)4]Cl, exhibits a square-pyramidal coordination of CuII by four N atoms of four imidazole ligands and one chlorine atom located at the apex of the pyramid.

Synthesis, Crystal Structures, Magnetic Properties and Photoconductivity of C60 and C70 Complexes with Metal Dialkyldithiocarbamates M(R2dtc)x, where M = CuII, CuI, AgI, ZnII, CdII, HgII, MnII, NiII, and PtII; R = Me, Et, and nPr

AbstractNew complexes of fullerenes C60 and C70 with metal dialkyldithiocarbamates, [M(R2dtc)x]·[C60(70)]·[Solvent], R = Et [M = CuII (C60, 1; C70, 2), CuI (C60, 3; C70, 4), AgI (C60, 5), ZnII (C60, 6), CdII (C60, 7; C70, 8), HgII (C60, 9), MnII (C70, 10)], R = Et and Me [M = CuII (C60, 11), and ZnII (C60, 12)], and R = nPr [M = CuII (C60, 13), NiII (C60, 14), and PtII (C60, 15)] were obtained. M(R2dtc)x efficiently cocrystallized with fullerene molecules as tetrahedral monomers (6, 12), dimers (1, 7, 11), and tetramers (3, 4). Fullerene molecules form closely packed hexagonal and square layers in 1, 7, and 11, hexagonal and tetragonal 3D structures in 6 and 12, and island motifs in 3 and 4. Complexes 1–15 have a neutral ground state. However, the formation of the complexes with fullerenes changes the environment of paramagnetic CuII and MnII. The EPR spectra of 1, 2, 11, and 13 are essentially modified relative to those of pristine Cu(R2dtc)2 because of a weak coordination of CuII to fullerene and a flattening of the central (NCS2)2Cu fragments. Complex 10 shows a spectrum exhibiting features from 50 to 600 mT and manifests strong antiferromagnetic coupling of spins with a Weiss temperature of –96 K and the maximum of magnetic susceptibility at 46 K. Such magnetic behavior can be explained by the formation of [Mn(Et2dtc)2]2 dimers in 10. The illumination of the crystals of 1, 2, and 7 by white light results in up to a 103 increase in photocurrent. The photoconductivity spectra have maxima at 470, 450–650, and 660 nm for 1, 2, and 7, respectively. Photogeneration of free charge carriers is realized by photoexcitation of Cu(Et2dtc)2 in 1 and 2, and by charge transfer from Cd(Et2dtc)2 to C60 molecules in 7. The decrease of photocurrent in 1 and 7 in a weak magnetic field with B0 < 0.5 T was found. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

UV resonance Raman study of model complexes of the CuB site of cytochrome c oxidase

A newly designed model complex for the CuB site of cytochrome c oxidase (CcO), that is, Cu coordinated by two free imidazoles and an imidazole covalently linked to p-cresol [CuIIBIAIPBr]Br, (BIAIP =2-[4-[[Bis(1-methyl-1H-imidazol-2-ylmethyl)amino]methyl]-1H-imidazol-1-yl]-4-methylphenol), and related molecules have been investigated with absorption and ultraviolet resonance Raman (UVRR) spectroscopy employing the excitation wavelengths between 220 and 290nm. Attention was focused on the electron delocalization through the cross-linkage between the phenol and imidazole rings, and the influences by the coordination of CuII to imidazole. In addition to the ν8a and ν8b modes of p-cresol, a number of Raman bands involving vibrations of the imidazole moiety have been intensity-enhanced despite Raman excitation in resonance with the π–π* transition of phenol, indicating appreciable mixing of the π systems of imidazole and phenol rings. Furthermore, two kinds of imidazoles seem to be differential; one is the imidazole linked to p-cresol which yielded Raman bands at 1249, 1191, and 1141cm−1 for protonated CuII-BIAIP, and the other is one not linked to p-cresol, which yielded an intense band at 1488cm−1 band. Raman enhancement of the latter mode seems to be caused by preresonance to the lowest π–π* transition of imidazole via the A-term mechanism. The Raman excitation profile (REP) of ν8a mode for the deprotonated phenol of the CuII-complex revealed a weak local maximum corresponding to the La band around 240nm. Raman enhancement by the La band was relatively weaker for the CuII-complex than for the ZnII-complex and metal-free ligand, suggesting the more extensive mixing of π systems of p-cresol-imidazole through the cross-linkage for the Cu II-complex.

Di-μ-salicylato-κ4O:O′-bis[(2,2′-bipyridine-κ2N,N′)copper(II)] bis(salicylic acid)

The title complex, [Cu2(C7H4O3)2(C10H8N2)2]·2C7H6O3, crystallizes as a centrosymmetric dimer containing two CuII atoms bridged by two phenolato O atoms from salicyl­ate ligands. Each CuII atom lies in an approximate square planar environment and is bonded to two N atoms of a 2,2′-bi­pyridine ligand, the phenolato O and the carboxyl­ato O atoms of a salicyl­ate ligand. The coordination of CuII is completed by bonding to a phenolato O atom in the axial direction, giving square pyramidal geometry. The dimer is stabilized by a strong intermolecular π–π interaction involving pairs of bi­pyridine ligands and a salicyl­ate ring. The crystal structure is stabilized by π–π interactions and hydrogen bonds.

A Facile Direct Synthesis of Bimetallic CuIIZnII Complexes with Ethylenediamine Revealing Different Types of Chain Crystal Structures

AbstractUnactivated copper metal powder and zinc oxide readily react with ethylenediamine (en) in nonaqueous [methanol, dimethylformamide (dmf), dimethyl sulfoxide (dmso), acetonitrile] solutions of ammonium salts under ambient conditions producing, in high yields, a series of heterobimetallic complexes of general formula [Cu(en)2ZnX4]·(Solv), where X = Cl, Br, NCS, CH3COO (OAc); Solv = dmf, dmso, CH3CN, H2O. The single‐crystal X‐ray analysis of the complexes reveals chain structures, which are based on the completion of the octahedral coordination of CuII by two bridging X atoms from ZnX42−. The ZnX42− is shown to be a distorted tetrahedron (Cl, Br, NCS) or a very distorted octahedron (OAc) and to behave as a one‐ or two‐linking centre bridging ligand. The chains are found to be zigzag [Cu(en)2ZnCl4]·dmso (1), [Cu(en)2ZnCl4]·dmf (2), [Cu(en)2Zn(NCS)4]·CH3CN (3), quasi linear [Cu(en)2Zn(OAc)4] (4), or helical, [Cu(en)2Zn(NCS)4]· 0.5H2O (5), depending on the nature of the anion and solvent. Complex 4 represents the first compound containing Zn(OAc)42− to be crystallographically authenticated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The Coordination of CuII in Zeolites − Structure and Spectroscopic Properties

Zeolites loaded with transition metal ions are promising heterogeneous catalysts. Knowledge about the location and structure of the metal centers is of paramount importance for the understanding of the catalytic potential of these materials. In this work, the spectroscopic studies of the coordination of CuII in zeolite A, ZK4, X, Y and mordenite are reviewed. Experimentally, diffuse reflectance spectroscopy (DRS) and electron spin resonance (ESR) spectroscopy have been applied to study the coordination of CuII in zeolites. Ab initio calculations on model clusters, representing the CuII sites in zeolites, are used for the interpretation of the experimental data. The combination of experimental spectroscopic information with theoretical results leads to a new and profound insight into the CuII−zeolite interaction.

A new functionalized hexaazamacrocycle. Effect of pyridine pendants on cation and anion binding

The macrocyclic ligand 1,4,7,13-tetramethyl-10,16-bis(o-pyridylmethyl)-1,4,7,10,13,16-hexaazacyclooctadecane (L) has been prepared and its protonation studied by means of potentiometric measurements. It binds up to five protons in aqueous solution above pH 2. The 1H and 13C NMR spectra at different pH values allowed the determination of the stepwise protonation sites. The first three protonation steps take place on amine groups of the macrocyclic structure, the fourth and fifth on the pyridine nitrogens. Co-ordination of CuII, ZnII, CdII and PbII in aqueous solution has been studied by means of potentiometric, 1H NMR and/or UV-vis measurements (0.1 M NaClO4, 298.1 K). The [ML]2+ complexes show unusually low stabilities, which are considered due to the low σ-donating properties of tertiary nitrogens as well as to the formation of large chelate rings containing unbound amine groups. The ligand behaves as a ditopic receptor for CuII. The [CuL]2+ complex exhibits a marked tendency to bind a second Cu2+ ion, giving binuclear complexes. Protonated forms of L are efficient receptors for ATP and ADP. The binding properties toward these anions are influenced by the presence of the two heteroaromatic moieties, which lead to a higher efficiency in ATP binding at acidic pH.

Co-ordination of copper(II) and nickel(II) ions by a novel open chain oxime ligand

Potentiometric spectroscopic and X-ray studies of the open chain oxime ligand, N,N′-bis(2-hydroxyimino-propionyl)propane-1,3-diamine and its complexes with NiII and CuII ions showed a very high efficacy of the ligand studied in the co-ordination of both CuII and NiII ions. The metal complexes are very stable and square-planar with four nitrogens involved in metal-ion binding. These complexes may be additionally stabilised by hydrogen bonds between two oxime oxygen atoms.

Generation of ion-exchange capacity by silicon incorporation into the aluminophosphate VPI-5/AIPO4-8 molecular sieve system

CuII ions have been ion-exchanged into SiVPI-5 and SAPO-8, which were synthesized by introducing SiO2 into the VPI-5 aluminosilicate synthesis mixture. The coordination of CuII during various stages of dehydration and reoxidation and its interaction with polar and non-polar adsorbate molecules were studied by EPR and electron spin–echo modulation spectroscopy. In comparison to CuII impregnated into VPI-5, a substantially higher ion-exchange capacity and better stabilization of the CuII ions by the framework was found in CuH-SiVPI-5, where CuII has been introduced by conventional aqueous solution ion exchange. Copper(II) ions coordinate directly to three molecules of water and two molecules of ammonia. However, CuII is also still coordinated to framework oxygens in these complexes, indicating a strong interaction of CuII with the framework. Non-polar bulky adsorbate molecules such as benzene do not coordinate directly to the CuII ions, but polar adsorbates such as pyridine are able to induce CuII migration from less accessible sites to the more accessible main channel, where direct coordination occurs. The differences between impregnated Cu/VPI-5 and ion-exchanged CuH-SiVPI-5 or SAPO-8 for dehydration behaviour and adsorbate interactions indicate successful incorporation of a small amount of silicon into the VPI-5 framework, which results in a material with enhanced ion-exchange capacity.

Syntheses, characterization, and structural chemistry of biladien-ac-10-one and -bc-5-one metal complexes with 4N or (3N + O) co-ordination

Transition-metal(II) complexes have been formed between Cu, Co, Pd, Hg, Cd, Zn and Ni and biladien-bc-5-ones or -ac-10-ones. All show spectroscopic and analytical data in accordance with the formation of 1 : 1 complexes. Reaction of 5- and 10-oxobiladienes with CuII, CoII, PdII, ZnII, CdII and HgII always gave complexes in which the metal is co-ordinated to the four pyrrole nitrogens (4N co-ordination) and led to a cyclic, helical conformation of the tetrapyrrole ligand. Reaction of biladien-ac-10-ones with NiII also gave the 4N-co-ordinated derivative. However, reaction of biladien-bc-5-ones with NiII gave two compounds, one being the 4N-co-ordinated complex and other a side product in which the metal is co-ordinated to three pyrrole nitrogens of the conjugated system and to the meso-oxygen atom of the oxobiladiene [(3N + O) co-ordination]. The latter co-ordination type was found to occur only when the C(19) position became substituted by nucleophiles such as OH or OMe leading to steric repulsion of the fourth pyrrole ring away from the metal. Single-crystal structure analyses were made for 10-oxobiladien-ac complexes with 4N co-ordination of CuII, PdII, NiII or CoII and for 5-oxobiladien-bc complexes with 4N co-rdination of PdII, CoII or CuII. These showed tetrahedrally distorted co-ordination geometries in the MN4 unit. The molecular structures of two nickel complexes of 5-oxobiladien-bc derivatives with square-planar (3N + O) co-ordination have also been determined.

Synthesis and coordination chemistry of 1-(2′,2″-bipyridyl-5′-yl-methyl)-1,4,8,11-tetraazacyclotetradecane L1. Quenching of fluorescence from [Ru(bipy)2(L1)]2+by coordination of NiIIor CuIIin the cyclam cavity (bipy = 2,2′-bipyridine; cyclam = 1,4,8,11-tetra-azacyclotetradecane)

A novel bipy derivative of cyclam (L1) designed for controlled and systematic polynuclear metal complex formation is reported; fluorescence quenching of the [Ru(bipy)3]2+ core of [(bipy)2Ru(L1)]2+ upon coordination of CuII at the cyclam cavity is demonstrated.

Synthesis, reactivity, structural studies and magnetic properties of 4-amino-1,4-dihydro-3-methyl-1,2,4-triazole-5-thione copper complexes

By reaction of CuCl2 with 4-amino-1,4-dihydro-3-methyl-1,2,4-triazole-5-thione (HL) in a 4 : 1 molar ratio and in a 12 mol dm–3 HCl medium, at room temperature, the complex [CuCl2(HL)]·H2O 1 was isolated in an orthorhombic form. With an excess of CuCl2 a polymeric complex [{Cu2Cl4(HL)}n]·nH2O 2 was isolated, while introduction of a bar of metallic copper gave a polymeric mixed-valence CuI–CuII(1 : 2) complex [{Cu3Cl5(OH2)(HL)2}n]·2nH2O 3. Crystals of 1 are orthorhombic, space group Pbca, a= 16.256(1), b= 15.611(2), c= 7.327(1)A and Z= 8. Crystals of 2 are orthorhombic, space group Pbca, a= 12.900(3), b= 12.965(5), c= 14.250(5)A and Z= 8. Crystals of 3 are monoclinic, space group P21/a, a= 34.099(8), b= 8.704(3), c= 7.163(3)A, β= 96.14(2)° and Z= 4. The structures have been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.0393, 0.0582 and 0.0467 for 1132, 1346 and 3177 observed reflections respectively. In 1 the triazole acts as a chelating ligand through the sulfur and the aminic nitrogen atoms and the co-ordination of CuII is fundamentally square planar. In 2 the ligand acts in a tridentate manner, chelating and bridging through the iminic nitrogen atom. The [Cu2Cl4(HL)] units can be considered as inner salts and are joined in a head-to-tail fashion forming zigzag polymeric chains. In 3 the two independent ligands present different behaviours; one chelates a CuII atom as in 1, while the other acts as a µ3 ligand chelating another CuII atom and bridging through the iminic nitrogen and the sulfur atoms two CuI atoms. The magnetic properties were investigated by measurements of electron paramagnetic resonance microwave absorption. For all compounds S=½ spectra were observed with spectroscopic g constants in the range ca. 2.05–2.20. The resulting single-ion g tensors are typical of a tetragonal elongated copper(II) ion where covalency plays a relevant role due to the presence of the SCNN chelating structure. The magnetic local axes deduced on this basis are strictly related to the copper co-ordination planes (obtained from the structural data) confirming the oxidation state II for all the copper atoms except for the tetrahedral CuI in 3.

Coordination geometries and cooperative ordering effects in copper(II) complexes with tridentate Schiff base dianions. I. Crystal and molecular structure and EPR investigation of N‐salicylideneglycinato‐2‐methylimidazole‐copper(II)

AbstractN‐Salicyclideneglycinato(2‐methylimidazole)copper (II) — [Cu(salgly)(2‐MeIm)] — C13H13N3O3Cu — crystallizes in the monoclinic space group P21/c, a = 1 248.4, b = 1 157.3, c = 964.5 pm, β = 108.91°, Z = 4; structure determination with 1 504 significant reflections, R = 0.058. The molecular stucture of the complex is characterized by an approximately square coordination of CuII with O, N, O atoms of the tridendate dianion salgly2⊖ and the 3‐N atom of 2‐MeIm. The coordination polyhedron is completed to square pyramid by an apically coordinated carboxyl oxygen atom (bond distance 248 pm) from the neighboring complex molecule, thus forming zigzag chains oriented on parallel lines in the crystal structure. The EPR parameters of the title compound (g = 2.176, g = 2.146, g = 2.056) confirm the slightly disturbed antiferrodistortive ordering of the complex molecules quantitatively. From the cooperative gc tensor of a single crystal and the structural data orthorhombic molecular g components were evaluated. They were refined, in order to achieve a still better agreement with the EPR parameters of a series of comparable copper(II) complexes.