Cu-N Bond Research Articles

Tetra-μ-acetato-bis[(1,3-benzothiazole)copper(II)](Cu—Cu)

The title compound, [Cu2(CH3CO2)4(C7H5NS)2] or [(C7H5NS)Cu]2(μ-O2CCH3)4, crystallizes with one mol­ecule per unit cell. The coordination number of copper is six with four basal O atoms, one axial N atom and one axial Cu atom. Four acetate ligands act as bidentate linker and connect two Cu atoms, with a crystallographic inversion center located at the mid-point of the Cu—Cu bond. The acetate ligands form slightly distorted square planes around each metal ion, while the copper ions are displaced by 0.2089 (4) Å from these planes towards the N atoms. Thus, the Cu—Cu distance is elongated to 2.6378 (7) Å, compared with the 2.2180 (7) Å distance between the two basal planes. The angle between the basal plane and the Cu—N bond is 4.84 (6)°.

{N,N′-[2,2′-(Ethane-1,2-diyldisulfanediyl)di-o-phenylene]bis(quinoline-2-carboxamidato)}copper(II)

In the title compound, [Cu(C34H24N4O2S2)] or [Cu(bqdapte)], where H2bqdapte is 1,2-{bis­[2-(quinoline-2-carboxamido)­phen­yl]sulfan­yl}ethane, the CuII ion is coordinated to the dianionic hexa­dentate bqdapte2− ligand by two amide and two quinoline N atoms and two thio­ether S atoms. In the observed conformation of the hexa­dentate ligand, the quinoline rings attain positions related by a twofold axis. The Cu atom displays a Jahn–Teller-distorted octa­hedral CuN4S2 geometry axially compressed along the two trans-configured Cu—Namidate bonds.

(E)-N′-(5-Chloro-2-oxidobenzylidene-κO)-3,4,5-trimethoxybenzohydrazidato-κ2N′,O](pyridine-κN)copper(II)

In the title compound, [Cu(C17H15ClN2O5)(C5H5N)], the CuII atom is coordinated by one N atom and two O atoms from an anionic salicyl­aldehyde benzoyl­hydrazone ligand and one pyridine N atom in a distorted square-planar geometry. The bonds displays the usual elongation with mean Cu—O and Cu—N bond lengths of 1.926 and 1.976 Å, respectively. The pyridine ring makes dihedral angles of 26.12 (13) and 11.08 (12)°, respectively, with the trimeth­oxy­phenyl and phenolate rings, which make a dihedral angle of 16.05 (12)° with one another.

The intramolecular aryl embrace: from light emission to light absorption

6-(1-Methylpyrrol-2-yl)-2,2'-bipyridine, 3, and 6-(selenophene-2-yl)-2,2'-bipyridine, 4, have been prepared and characterized in solution and by structural determinations. Copper(I) complexes [CuL(2)][PF(6)] in which L is 2,2'-bipyridine substituted in the 6-position by furyl, thienyl, N-methylpyrrolyl, selenopheneyl, methyl or phenyl, (L = 1-6) have been synthesized. The complexes have been characterized by electrospray mass spectrometry, and solution NMR and UV-VIS spectroscopies. The single crystal structures of [Cu(1)(2)][PF(6)], [Cu(2)(2)][PF(6)], [Cu(3)(2)][PF(6)], [Cu(5)(2)][PF(6)] and [Cu(6)(2)][PF(6)] have been determined. In those compounds containing an aromatic substituent attached to the bpy unit, the substituent is twisted with respect to the latter. In [Cu(3)(2)][PF(6)] and [Cu(5)(2)][PF(6)], this results in intra-cation π-stacking between ligands which is very efficient in [Cu(3)(2)](+) despite the steric requirements of the N-methyl substituents. Face-to-face stacking between the ligands in the [Cu(2)(2)](+) ion is achieved by complementary substituent twisting and elongation of one Cu-N bond, but there is no analogous intra-cation π-stacking in [Cu(1)(2)](+). Ligand exchange reactions between [CuL(2)][PF(6)] (L = 1-6) and TiO(2)-anchored ligands 7-10 (L' = 2,2'-bipyridine-based ligands with CO(2)H or PO(OH)(2) anchoring groups) have been applied to produce 24 surface-anchored heteroleptic copper(i) complexes, the formation of which has been evidenced by using MALDI-TOF mass spectrometry and thin layer solid state diffuse reflectance electronic absorption spectroscopy. The efficiencies of the complexes as dyes in DSCs have been measured, and the best efficiencies are observed for [CuLL'] with L' = 10 which contains phosphonate anchoring groups.

Cyano-Bridged Pentanuclear and Honeycomblike MIIICuII (M = Fe, Cr) Bimetallic Assemblies: Structural Variations Modulated by Side Groups of Macrocyclic Ligands and Magnetic Properties

Three two-dimensional (2D) layered M(III)-Cu(II) (M = Fe, Cr) bimetallic complexes and a discrete cluster were prepared using [M(CN)(6)](3-) and respective Cu macrocycles with methyl (1, 3) or ethyl (2, 4) side groups. The crystal structures can be described as aesthetic honeycomb-like M(2)Cu(3) neutral sheets (1, 3, 4) and a pentanuclear Fe(2)Cu(3) entity (2) with an isolated Cu(L2)(2+) moiety. The steric hindrance induced by the pendant groups renders the internal parameters of the Cu-N(ax) (where the "ax" subscript denotes axial) length and Cu-N(ax)-C(ax) angle to become elongated and acute. The magnetic data disclose that ferromagnetic couplings are transmitted between M(III) and Cu(II) ions through the CN links. For 4, particularly, there is a magnetically defined chain (J(c)) composed of dimers (J(d)) and trimers (J(t)), based on the structural considerations. The intramolecular magnetic coupling constants are J(d) = 3.73 cm(-1) and J(t) = 4.08 cm(-1), while the J(c) value corresponds to 0.17 cm(-1). From a magnetostructural point of view, it is reasoned that the Cu-N(ax) bond length is probably a determining factor of the strength of magnetic couplings in 4.

Low-temperature X-ray diffraction study of [CuII(1,10-C12H8N2)3]2+{CoIII[η5-(3)-1,2-C2B9H11]2} 2 − ·CH3CN

Single crystal XRD is used to study the crystal structure of a new compound containing the dicarbollyl cluster anion Co(III) with the composition [CuPhen3][Co(C2B9H11)2]2·CH3CN, where Phen is 1,10-phenanthroline. The crystallographic data: C46H71B36N7Co2Cu, M = 1292.66, monoclinic system, P21/c space group, unit cell parameters a = 14.7178(2) A, b = 19.5640(4) A, c = 22.8663(5) A, β = 106.6601(7)°, V = 6307.75(33) A3, Z = 4, dx = 1.361 g/cm3, T = 100 K, μ = 0.90 mm−1. The structure is solved by the direct method and refined by the full-matrix LSM in an anisotropic-isotropic (for H atoms) approximation up to the final agreement factors R1 = 0.0370, wR2 = 0.0869 for 13,807 Ihkl ≥ 2 σI out of 18,295 measured Ihkl. The structure consists of [CuPhen3] cations, Co(C2B9H11)2 anions, and acetonitrile molecules MeCN. The central Cu atom in the cation in the general position, and its coordination geometry is a distorted extended octahedron formed by six nitrogen atoms of the three bidentate Phen ligands. The coordination of Cu(II) in the cation is (2+2+2) with two long axial and four shorter equatorial Cu-N bonds, whose average lengths are 2.239(2) A and 2.077(1) A respectively. Each anion has its own position of the -C2-groups; for Co(1), it is a quasi-gauche-configuration; for Co(2), a quasi-trans-configuration.

N-(3-Methoxy-2-oxidobenzylidene-κO2)leucinato-κ2N,O](1,10-phenanthroline-κ2N,N′)copper(II) monohydrate

The asymmetric unit of the title complex, [Cu(C14H17NO4)(C12H8N2)]·H2O, contains two independent CuII complex mol­ecules and two uncoordinated water mol­ecules. In each complex mol­ecule, the Cu atom is O,N,O′-chelated by the tridentate Schiff base ligand and N,N′-chelated by the 1,10-phenanthroline ligand in a distorted square-pyramidal geometry. The Cu—N bond distances in the apical directions are 2.298 (4) and 2.268 (4) Å. In the crystal, inter­molecular O—H⋯O and C—H⋯O hydrogen bonds together with C—H⋯π inter­actions result in a three-dimensional supra­molecular structure.

Bis{μ-N-[(dimethylamino)dimethylsilyl]-2,6-dimethylanilido}-κ2N:N′;κ2N′:N-dicopper(I)

The title compound, [Cu2(C12H21N2Si)2], is a binuclear CuI complex. The dimeric mol­ecule has an inversion center located at the mid-point of the Cu—Cu bond [Cu—Cu = 2.7209 (7) Å]. The bidentate ligand behaves in an N:N′-bridging mode, coordinating the metal atoms. The N—Cu—N unit is close to being linear [176.60 (8)°]. The two N atoms exhibit different affinities for the metal atom. The Cu—Namino bond is longer than the Cu—Nanilido bond by 0.079 Å. The core of the mol­ecule, the [Cu—N—Si—N]2 eight-membered ring, adopts a chair configuration.

Structural Characterization of a Copper Nitrosyl Complex with a {CuNO}10 Configuration

The synthesis and characterization of a {CuNO}(10) complex, namely, [Cu(CH(3)NO(2))(5)(NO)][PF(6)](2), has been achieved by the addition of [NO][PF(6)] to copper metal powder in the presence of nitromethane. In the solid state, this complex exhibits a bent Cu-N-O moiety [Cu-N-O = 121.0(3)°] and a long Cu-N bond. This complex readily reacts with mesitylene to form [mesitylene, NO][PF(6)] and [Cu(η(2)-1,3,5-Me(3)C(6)H(3))(2)][PF(6)] by transfer of NO(+) to the mesitylene ring.

Hydrogen and Copper Ion Induced Molecular Reorganizations in Two New Scorpiand-Like Ligands Appended with Pyridine Rings

The synthesis of two new ligands constituted of a tris(2-aminoethyl)amine moiety linked to the 2,6 positions of a pyridine spacer through methylene groups in which the hanging arm is further functionalized with a 2-pycolyl (L1) or 3-pycolyl (L2) group is presented. The protonation of L1 and L2 and formation of Cu(2+) complexes have been studied using potentiometric, NMR, X-ray, and kinetic experiments. The results provide new information about the relevance of molecular movements in the chemistry of this kind of so-called scorpiand ligand. The comparison between these two ligands that only differ in the position of the substituent at the arm reveals important differences in both thermodynamic and kinetic properties. The Cu(2+) complex with L1 is several orders of magnitude more stable than that with L2, surely because in the latter case the pyridine nitrogen at the pendant arm is unable to coordinate to the metal ion with the ligand acting as hexadentate, a possibility that occurs in the case of [CuL1](2+), as demonstrated by its crystal structure. Significant differences are also found between both ligands in the kinetic studies of complex formation and decomposition. For L1, those processes occur in a single kinetic step, whereas for L2 they occur with the formation of a detectable reaction intermediate whose structure corresponds to that resulting from the movement typical of scorpiands. Another interesting conclusion derived from kinetic studies on complex formation is that the reactive form of the ligand is H(3)L(3+) for L1 and H(2)L(2+) for L2. DFT calculations are also reported, and they allow a rationalization of the kinetic results relative to the reactive forms of the ligands in the process of complex formation. In addition, they provide a full picture of the mechanistic pathway leading to the formation of the first Cu-N bond, including outer-sphere complexation, water dissociation, and reorganization of the outer-sphere complex.

Copper(II) chloride and bromide complexes with 2-methyl-2H-tetrazol-5-amine: an X-ray powder diffraction study

The complex catena-poly[[dibromidocopper(II)]-bis(mu-2-methyl-2H-tetrazol-5-amine)-kappa(2)N(4):N(5);kappa(2)N(5):N(4)], [CuBr(2)(C(2)H(5)N(5))(2)](n), (I), and the isotypic chloride complex catena-poly[[dichloridocopper(II)]-bis(mu-2-methyl-2H-tetrazol-5-amine)-kappa(2)N(4):N(5);kappa(2)N(5):N(4)], [CuCl(2)(C(2)H(5)N(5))(2)](n), (II), were investigated by X-ray powder diffraction at room temperature. The crystal structure of (I) was solved by direct methods, while the Rietveld refinement of (II) started from the atomic coordinates of (I). In both structures, the Cu atoms lie on inversion centres, adopting a distorted octahedral coordination of two halogen atoms, two tetrazole N atoms and two 5-amine group N atoms. Rather long Cu-N(amine) bonds allow consideration of the amine group as semi-coordinated. The compounds are one-dimensional coordination polymers, formed as a result of 2-methyl-2H-tetrazol-5-amine ligands bridging via a tetrazole N atom and the amine N atom. In the polymeric chains, adjacent Cu atoms are connected by two such bridges.

Di-μ-acetato-bis[(acetato-κ2O,O′)bis(isonicotinamide-κN)copper(II)

The title centrosymmetric bimetallic complex, [Cu2(C2H3O2)4(C6H6N2O)4], is composed of two copper(II) cations, four acetate anions and four isonicotinamide (INA) ligands. The asymmetric unit contains one copper cation to which two acetate units bind asymmetrically; one of the Cu—O distances is rather long [2.740 (2) Å], almost at the limit of coordination. These Cu—O bonds define an equatorial plane to which the Cu—N bonds to the INA ligands are almost perpendicular, the Cu—N vectors subtending angles of 2.4 (1) and 2.3 (1)° to the normal to the plane. The metal coordination geometry can be described as a slightly distorted trigonal bipyramid if the extremely weak Cu—O bond is disregarded, or as a highly distorted square bipyramid if it is not. The double acetate bridge between the copper ions is not coplanar with the CuO4 equatorial planes, the dihedral angle between the (O—C—O)2 and O—Cu—O groups being 34.3 (1)°, resulting in a sofa-like conformation for the 8-member bridging loop. In the crystal, N—H⋯O hydrogen bonds occur, some of which generate a head-to tail-linkage between INA units, giving raise to chains along [101]; the remaining ones make inter-chain contacts, defining a three-dimensional network. There are in addition a number of C—H⋯O bonds involving aromatic H atoms. Probably due to steric hindrance, the aromatic rings are not involved in significant π⋯π inter­actions.

Catena-Poly[[pyridinecopper(II)]-μ-N-[(2-oxido-1-naphthyl)methylene]glycinato

In the title compound, [Cu(C13H9NO3)(C5H5N)], the CuII atom is coordinated in a distorted square-pyramidal geometry, with two N and two O atoms in the basal positions and one O atom in the apical position. The apical Cu—O bond [2.3520 (16) Å] is much longer than the basal Cu—O and Cu—N bonds [1.9139 (14)–2.0136 (17) Å]. The carboxyl­ate group bridges CuII atoms, forming a zigzag chain along the a axis.

Copper(I) complex with α-(3,3-dimethyl-3,4-dihydroisoquinolyl-1)hydroxyiminoacetonitrile [Cu(LH)L]2 · CH3CN: Synthesis, crystal structure, and spectroscopic characteristics

The complex of univalent copper with α-(3,3-dimethyl-3,4-dihydroisoquinolyl-1)hydroxyiminoacetonitrile (LH) is synthesized and studied by X-ray diffraction and IR spectroscopy. As shown by X-ray diffraction analysis, structural crystal units are a binuclear complex consisting of two independent [Cu(LH)L] molecules joined by very strong hydrogen bonds O-H⋯O and an acetonitrile solvate molecule: [Cu(LH)L]2 · CH3CN (I). The ligands coordinate the copper(I) atom at the vertices of a flattened tetrahedron in the bidentate-chelating mode through their nitrogen atoms. The two independent ligands are linked to each copper atom, and one of the ligands exists in the molecular form LH, whereas the other exists in the form of the L− anion. The Cu-N bond lengths range from 1.995 to 2.051 A, and the NCuN angles are 80.7°–132.8°. All ligands exist in the same E-s-cis isomeric form. The IR spectroscopic characteristics of the complex are presented.

Chloridobis(2,9-diethoxy-1,10-phenanthroline-κ2N,N′)copper(II) perchlorate

In the title complex, [CuCl(C16H16N2O2)2]ClO4, the CuII ion is coordinated by four N atoms from two chelating 2,9-dieth­oxy-1,10-phenanthroline ligands and one chloride ion in a slightly disorted trigonal-bipyramidal environment. Two N atoms and the Cl atom are in equatorial positions while the remaining two N atoms occupy apical sites, the equatorial Cu—N bonds being significantly longer than the two apical Cu—N bonds. The N=C—O—C torsion angles involving the four eth­oxy groups are in the range 161.5 (8) to 177.0 (5)°. In the crystal structure, there are significant π–π stacking inter­actions between inversion-related rings of phenanthroline groups with centroid–centroid distances in the range 3.649 (4)–3.790 (4) Å.

Crystal and molecular structure of four copper(II) ethylenediaminedisuccinates, [Cu2(RR,SS-Edds)] · 6H2O, Ba2[Cu(RR,SS-Edds)](ClO4)2 · 8H2O, Ba[Cu(SS-HEdds)]ClO4 · 2H2O, and Ba3[Cu2(RR,SS-Edds)2](ClO4)2 · 6H2O

Four Cu(II) complexes with the RR,SS-Edds4− and SS-HEdds3− anions are synthesized, and their crystal structures are studied. In the compounds [Cu2(RR,SS-Edds)] · 6H2O (I) and Ba2[Cu(RR,SS-Edds)](ClO4)2 · 8H2O (II), the ligand forms hexacoordinate chelate [Cu(Edds)]2− complexes with the N atoms and O atoms of the propionate groups in the equatorial positions and the O atoms of the acetate groups in the axial vertices. In the compounds Ba[Cu(SS-HEdds)]ClO4 · 2H2O (III) and Ba3[Cu2(RR,SS-Edds)2](ClO4)2 · 6H2O (IV), one of the propionate arms, the protonated arm in III and the deprotonated arm in IV, does not enter into the coordination sphere of the Cu atom. An acetate arm moves to its position in the equatorial plane, and the free axial vertex is occupied by an O atom of the perchlorate ion. In I–IV, the lengths of the equatorial Cu-N and Cu-O bonds fall in the ranges 1.970–2.014 and 1.921–1.970 A, respectively. The axial Cu-O bonds with the acetate groups and ClO4− anions are elongated to 2.293–2.500 and 2.727–2.992 A, respectively. In structure I, the second Cu atom acts as a counterion forming bonds with the O atoms of two water molecules and three O atoms of the Edds ligands. In II–IV, the Ba2+ cations are hydrated and bound to the O atoms of the anionic complexes and (except for one of the cations in IV) ClO4− anions. The coordination number of the Ba cations is nine. The structural units in I–IV are connected into layers. In I, an extended system of hydrogen bonds links the layers into a framework. In II and III, the layers are linked only by weak hydrogen bonds, one bond per structural unit. In IV, ClO4− anions are bound to the Ba and Cu atoms of neighboring layers, thus serving as bridges between the layers.

Molecular Basis of the Bohr Effect in Arthropod Hemocyanin

Flash photolysis and K-edge x-ray absorption spectroscopy (XAS) were used to investigate the functional and structural effects of pH on the oxygen affinity of three homologous arthropod hemocyanins (Hcs). Flash photolysis measurements showed that the well-characterized pH dependence of oxygen affinity (Bohr effect) is attributable to changes in the oxygen binding rate constant, k(on), rather than changes in k(off). In parallel, coordination geometry of copper in Hc was evaluated as a function of pH by XAS. It was found that the geometry of copper in the oxygenated protein is unchanged at all pH values investigated, while significant changes were observed for the deoxygenated protein as a function of pH. The interpretation of these changes was based on previously described correlations between spectral lineshape and coordination geometry obtained for model compounds of known structure (Blackburn, N. J., Strange, R. W., Reedijk, J., Volbeda, A., Farooq, A., Karlin, K. D., and Zubieta, J. (1989) Inorg. Chem., 28, 1349-1357). A pH-dependent change in the geometry of cuprous copper in the active site of deoxyHc, from pseudotetrahedral toward trigonal was assigned from the observed intensity dependence of the 1s --> 4p(z) transition in x-ray absorption near edge structure (XANES) spectra. The structural alteration correlated well with increase in oxygen affinity at alkaline pH determined in flash photolysis experiments. These results suggest that the oxygen binding rate in deoxyHc depends on the coordination geometry of Cu(I) and suggest a structural origin for the Bohr effect in arthropod Hcs.

A novel three-dimensional coordination polymer constructed from pyrazine and copper(I): poly[[copper(I)-di-μ2-pyrazine-κ4N:N′] 3,5-dicarboxybenzenesulfonate monohydrate

In the title metal-organic framework complex, {[Cu(C(4)H(4)N(2))(2)](C(8)H(5)O(7)S).H(2)O}(n) or {[Cu(I)(pyz)(2)](H(2)SIP).H(2)O}(n) (pyz is pyrazine and H(3)SIP is 5-sulfoisophthalic acid or 3,5-dicarboxybenzenesulfonic acid), the asymmetric unit is composed of one copper(I) center, one whole pyrazine ligand, two half pyrazine ligands lying about inversion centres, one H(2)SIP(-) anion and one lattice water molecule, wherein each Cu(I) atom is in a slightly distorted tetrahedral coordination environment completed by four pyrazine N atoms, with the Cu-N bond lengths in the range 2.017 (3)-2.061 (3) A. The structure features a three-dimensional diamondoid network with one-dimensional channels occupied by H(2)SIP(-) anions and lattice water molecules. Interestingly, the guest-water hydrogen-bonded network is also a diamondoid network, which interpenetrates the metal-pyrazine network.

2-Oxo-1,2-dihydropyrimidin-3-ium di-μ-chlorido-bis{dichloridobis[pyrimidin-2(1H)-one-κN3]cuprate(II)} dihydrate

The asymmetric unit of the title compound, (C4H5N2O)2[Cu2Cl6(C4H4N2O)2]·2H2O, consists of one cation, one half of a centrosymmetric dianion and one water mol­ecule. The centrosymmetric dianion formed by dimerization in the crystal structure has neutral pyrimidin-2-one ligands coordinated to each copper(II) centre through Cu—N bonds. The Cu atoms each have a distorted trigonal bipyramidal geometry, with the N atom of the pyrimidin-2-one ligand in an axial position, and dimerize by sharing two equatorial Cl atoms. N—H⋯Cl, O—H⋯Cl and N—H⋯O hydrogen bonds connect the anions, cations and water mol­ecules, forming a three-dimensional network.

Low-dimensional compounds containing cyano groups. XVI. (Dicyanamido-κN1)bis(1,10-phenanthroline-κ2N,N′)copper(II) tetrafluoridoborate

The title compound, [Cu{N(CN)(2)}(C(12)H(8)N(2))(2)]BF(4), was prepared as part of our study of the shape of coordination polyhedra in five-coordinated copper(II) complexes. Single-crystal X-ray analysis reveals that the structure consists of [Cu{N(CN)(2)}(phen)(2)](+) cations (phen is 1,10-phenanthroline) and BF(4)(-) anions. The Cu centre is five-coordinated in a distorted trigonal bipyramidal manner by four N atoms of two phen ligands and one N atom of a dicyanamide anion, which is coordinated in the equatorial plane at a distance of 1.996 (2) A. The two axial Cu-N(phen) distances have similar values [average 1.994 (6) A] and are shorter than the two equatorial Cu-N(phen) bonds [average 2.09 (6) A]. This work demonstrates the effect of ligand rigidity on the shape of coordination polyhedra in five-coordinated copper(II) complexes.