Efficient stabilization of copper(III) in tetraaza pseudo-macrocyclic oxime-and-hydrazide ligands with adjustable cavity size

Spectroscopic characterization and reactivity studies of a copper(II) iminoxyl radical complex

A CuII complex (1) of a bis-pyridine-dioxime ligand and its one-electron oxidized analog (1-ox) were thoroughly characterized by various spectroscopic techniques, including X-ray absorption spectroscopy. 1-ox was found to be a CuII complex of a ligand iminoxyl radical and represents the first example of such a type. Reorganization energy (λ) of 2.12 eV was determined for the 1-ox/1 couple, which is considerably higher than the type 1 protein and synthetic CuIII/II(OH) complexes.

Old Acquaintances and Novel Complex Structures for the Ni(II) and Cu(II) Complexes of bis-Chelate Oxime-Amide Ligands

In the process of systematically studying the methylhydroxyiminoethaneamide bis-chelate ligands with polymethylene spacers of different lengths, L1-L3, and their transition metal complexes, a number of new Ni(II) and Cu(II) species have been isolated, and their molecular and crystal structures were determined using single-crystal X-ray diffraction. In all of these compounds, the divalent metal is coordinated by the ligand donor atoms in a square-planar arrangement. In addition, a serendipitously discovered new type of neutral Ni(II) complex, where the propane spacer of ligand L2 underwent oxidation to the propene spacer, and one of the amide groups was oxidised to the ketoimine, is also reported. The resulting ligand L2' affords the formation of neutral planar Ni(II) complexes, which are assembled in the solid state on top of each other, and yield two polymorphic structures. In both structures, the resulting infinite, exclusively parallel metal ion columns in ligand insulation may serve as precursor materials for sub-nano-conducting connectors. Overall, this paper reports the synthesis and characterisation of seven new anionic, cationic, and neutral Ni(II) and Cu(II) complexes, their crystal structures, as well as experimental and computed UV-Vis absorption spectra for two structurally similar Ni(II) complexes, yellow and red.

Crystal structure, Hirshfeld surface analysis and geometry optimization of 2-hy-droxy-imino-N-[1-(pyrazin-2-yl)ethyl-idene]propano-hydrazide

In the mol-ecule of the title compound, C9H11N5O2, the oxime and hydrazide groups are situated in a cis-position in relation to the C-C bond linking the two functional groups. The CH3C(=NOH)C(O)NH fragment deviates from planarity because of a twist between the oxime and amide groups. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming zigzag chains in the [013] and [03] directions.

Informing our Understanding of the Copper-Cuprizone Reaction with Computational Chemistry

The reaction of copper with bis(cyclohexanone)oxaldihydrazone (cuprizone) is a challenging coordination chemistry problem that has confounded attempts at elucidation for the past 70 years. The product of the reaction, a...

A second solvatomorph of poly[[μ4-N,N'-(1,3,5-oxadiazinane-3,5-di-yl)bis-(carbamoyl-methano-ato)]nickel(II)dipotassium]: crystal structure, Hirshfeld surface analysis and semi-empirical geometry optimization

The title compound, poly[tri-aqua-bis-[μ4-N,N'-(1,3,5-oxadiazinane-3,5-di-yl)bis(carbamoyl-methano-ato)]dinickel(II)tetra-potassium], [K4Ni2(C7H6N4O7)2(H2O)3] n , is a second solvatomorph of poly[(μ4-N,N'-(1,3,5-oxadiazinane-3,5-di-yl)bis-(carbamoyl-methano-ato)nickel(II)dipotassium] reported previously [Plutenko et al. (2021 ▸). Acta Cryst. E77, 298-304]. The asymmetric unit of the title compound includes two structurally independent complex anions [Ni(C7H6N4O7)]2-, which exhibit an L-shaped geometry and consist of two almost flat fragments perpendicular to one another: the 1,3,5-oxadiazinane fragment and the fragment including other atoms of the anion. The central Ni atom is in a square-planar N2O2 coordination arrangement formed by two amide N and two carboxyl-ate O atoms. In the crystal, the title compound forms a layered structure in which layers of negatively charged complex anions and positively charged potassium cations are stacked along the a-axis direction. The polymeric framework is stabilized by a system of hydrogen-bonding inter-actions in which the water mol-ecules act as donors and the carb-oxy-lic, amide and water O atoms act as acceptors.

Expanding manganese(IV) aqueous chemistry: unusually stable water-soluble hexahydrazide clathrochelate complexes

Mn cage complexes are rare, and the ones successfully isolated in the solid state are not stable in water and organic solvents. Herein, we present the first report of mononuclear Mn clathrochelates, in which the encapsulated metal exists in the oxidation state +4. The complexes are extremely stable in the crystalline state and in solutions and show rich redox chemistry.

Crystal structure and Hirshfeld surface analysis of poly[[bis-[μ4-N,N'-(1,3,5-oxadiazinane-3,5-di-yl)bis(carbamoyl-methano-ato)]nickel(II)tetra-potassium] 4.8-hydrate]

The title compound, {[K4Ni2(C7H6N4O7)2]·4.8H2O} n , was obtained as a result of a template reaction between oxalohydrazide-hydroxamic acid, formaldehyde and nickel(II) nitrate followed by partial hydrolysis of the formed inter-mediate. The two independent [Ni(C7H6N4O7)]2- complex anions exhibit pseudo-C S symmetry and consist of an almost planar metal-containing fragment and a 1,3,5-oxadiazinane ring with a chair conformation disposed nearly perpendicularly with respect to the former. The central NiII atom has a square-planar N2O2 coordination arrangement formed by two amide N and two carboxyl-ate O atoms. In the crystal, the nickel(II) complex anions form layers parallel to the ab plane. Neighboring complex anion layers are connected by layers of potassium cations for which two of the four independent cations are disordered over two sites [ratios of 0.54 (3):0.46 (3) and 0.9643 (15):0.0357 (15)]. The framework is stabilized by an extensive system of hydrogen bonds where the water mol-ecules act as donors and the carb-oxy-lic O atoms, the amide O atoms and the oxadiazinane N atoms act as acceptors.

The Myth of d8 Copper(III)

Seventeen Cu complexes with formal oxidation states ranging from CuI to CuIII are investigated through the use of multiedge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations. Analysis reveals that the metal-ligand bonding in high-valent, formally CuIII species is extremely covalent, resulting in Cu K-edge and L2,3-edge spectra whose features have energies that complicate physical oxidation state assignment. Covalency analysis of the Cu L2,3-edge data reveals that all formally CuIII species have significantly diminished Cu d-character in their lowest unoccupied molecular orbitals (LUMOs). DFT calculations provide further validation of the orbital composition analysis, and excellent agreement is found between the calculated and experimental results. The finding that Cu has limited capacity to be oxidized necessitates localization of electron hole character on the supporting ligands; consequently, the physical d8 description for these formally CuIII species is inaccurate. This study provides an alternative explanation for the competence of formally CuIII species in transformations that are traditionally described as metal-centered, 2-electron CuI/CuIII redox processes.

Indefinitely stable iron(IV) cage complexes formed in water by air oxidation

In nature, iron, the fourth most abundant element of the Earth's crust, occurs in its stable forms either as the native metal or in its compounds in the +2 or +3 (low-valent) oxidation states. High-valent iron (+4, +5, +6) compounds are not formed spontaneously at ambient conditions, and the ones obtained synthetically appear to be unstable in polar organic solvents, especially aqueous solutions, and this is what limits their studies and use. Here we describe unprecedented iron(IV) hexahydrazide clathrochelate complexes that are assembled in alkaline aqueous media from iron(III) salts, oxalodihydrazide and formaldehyde in the course of a metal-templated reaction accompanied by air oxidation. The complexes can exist indefinitely at ambient conditions without any sign of decomposition in water, nonaqueous solutions and in the solid state. We anticipate that our findings may open a way to aqueous solution and polynuclear high-valent iron chemistry that remains underexplored and presents an important challenge.

Crystal structure of 2-{[(E)-(4-anilinophen-yl)iminium-yl]meth-yl}-5-(di-ethyl-amino)-phenolate

The title compound, C₂₃H₂₅N₃O, crystallized with one single mol­ecule in the asymmetric unit and present in the zwitterionic form. In the crystal, mol­ecules are connected by N—H⋯O hydrogen bonds generating –A–B–A–B– zigzag chains extending along [010]. The chains are linked via C—H⋯π inter­actions and π–π inter­actions [with a centroid–centroid distance of 3.444 (3) Å)] between the benzene ring and the imino group of symmetry-related mol­ecules, forming slabs lying parallel to (100).

The title compound, C₂₃H₂₅N₃O, crystallized with one single mol­ecule in the asymmetric unit and is present in the zwitterionic form. There is an intra­molecular N—H⋯O hydrogen bond in the mol­ecule with the phenol ring being inclined to the central benzene ring by 20.67 (14)°. The terminal amino­phenyl ring forms a dihedral angle of 54.21 (14)° with the central benzene ring. The two outer aromatic rings are inclined to one another by 74.54 (14)°. In the crystal, the mol­ecules are connected by N—H⋯O hydrogen bonds, with adjacent molecules related by a 2₁ screw axis, generating –A–B–A–B– zigzag chains extending along [010]. The chains are linked via C—H⋯π and π–π inter­actions [with a centroid–centroid distance of 3.444 (3) Å] between the benzene ring and the imino group of symmetry-related mol­ecules, forming slabs lying parallel to (100).

Crystal structure of 2-amino-1,3-di-bromo-6-oxo-5,6-di-hydro-pyrido[1,2-a]quinoxalin-11-ium bromide monohydrate

In the title hydrated salt, C12H8Br2N3O(+)·Br(-)·H2O, which was synthesized by the reaction of the pyridine derivative Schiff base N (1),N (4)-bis-(pyridine-2-yl-methyl-ene)benzene-1,4-di-amine with bromine, the asymmetric unit contains a 2-amino-1,3-di-bromo-6-oxo-5,6-di-hydro-pyrido[1,2-a]quinoxalin-11-ium cation, with a protonated pyridine moiety, a bromide anion and a water mol-ecule of solvation. The cation is non-planar with the di-bromo-substituted benzene ring, forming dihedral angles of 24.3 (4) and 11.5 (4)° with the fused pyridine and pyrazine ring moieties, respectively. In the crystal, the cations are linked through a centrosymmetric hydrogen-bonded cyclic R 4 (2)(8) Br2(H2O)2 unit by N-H⋯Br, N-H⋯O and O-H⋯Br hydrogen bonds, forming one-dimensional ribbons extending along b, with the planes of the cations lying parallel to (100).

Crystal structure of di-chlorido-{N (1)-phenyl-N (4)-[(quinolin-2-yl-κN)methylidene]benzene-1,4-diamine-κN (4)}mercury(II)

In the mononuclear title complex, [HgCl2(C22H17N3)], synthesized from the quinoline-derived Schiff base N (1)-phenyl-N (4)-[(quinolin-2-yl)methyl-idene]benzene-1,4-di-amine (PQMBD) and HgCl2, the coordination sphere around the Hg(2+) atom is distorted tetra-hedral, comprising two Cl atoms [Hg-Cl = 2.3487 (14) and 2.4490 (15) Å] and two N atom donors from the PQMBD ligand, viz. the quinolyl and the imine N atom [Hg-N = 2.270 (4) and 2.346 (4) Å, respectively]. The dihedral angle between the two benzene rings attached to the amino group is 43.7 (3)°. In the crystal, N-H⋯Cl and C-H⋯Cl hydrogen bonds, as well as π-π stacking inter-actions between one phenyl ring and the pyridine ring of the quinoline moiety of an adjacent mol-ecule [centroid-to-centroid separation = 3.617 (4) Å] are observed, resulting in a three-dimensional network.

Crystal structure of aqua[N-(2-oxidobenzyl-κO)-l-leucinato-κ(2) N,O](1,10-phenanthroline-κ(2) N,N')-nickel(II) penta-hydrate

In the title compound, [Ni(C13H17NO3)(C12H8N2)(H2O)]·5H2O, the Ni(II) atom is in a distorted octa-hedral coordination environment provided by the two N atoms of one bidentate phenanthroline ligand and two O atoms and one N atom from a tridentate 2-[(2-hy-droxy-benz-yl)amino]-4-methyl-penta-noic acid (HAMA) ligand and one water mol-ecule. The complex was prepared by the reaction of nickel(II) nitrate with HAMA in the presence of 1,10-phenanthroline in a 1:1:1 ratio. In the crystal, the complex mol-ecules and solvate water mol-ecules are associated via O-H⋯O hydrogen bonds into a three-dimensional network.

Crystal structure of 2-azaniumyl-3-bromo-6-oxo-5,6-dihydropyrido[1,2-a]quinoxalin-11-ium dibromide

The title salt, C₁₂H₁₀BrN₃O²⁺·2Br⁻, was synthesized from the reaction of N¹,N⁴-bis­(pyridin-2-yl­methyl­idene)benzene-1,4-di­amine and bromine in a methanol solution. All non-H atoms of the 2-aza­niumyl-3-bromo-6-oxo-5,6-di­hydro­pyrido[1,2-a]quinoxalin-11-ium cation are nearly coplanar, the maximum deviation being 0.114 (4) Å. In the crystal, the cations and anions are linked through N—H⋯Br hydrogen bonds and weak C—H⋯Br inter­actions, forming a three-dimensional supra­molecular architecture. A short Br⋯Br contact [3.3088 (9) Å] is observed in the crystal.

Crystal structure of 2-hy-droxy-imino-2-(pyridin-2-yl)-N'-[1-(pyridin-2-yl)ethyl-idene]acetohydrazide

The mol­ecule of the title compound is approximately planar with the planes of the two pyridine rings inclined to one another by 5.51 (7)°. In the crystal, mol­ecules are linked by bifurcated O—H⋯(O,N) hydrogen bonds, forming inversion dimers, which are in turn linked via C—H⋯O and C—H⋯N hydrogen bonds, forming sheets lying parallel to (502).

The mol­ecule of the title compound, C₁₄H₁₃N₅O₂, is approximately planar (r.m.s deviation for all non-H atoms = 0.093 Å), with the planes of the two pyridine rings inclined to one another by 5.51 (7)°. The oxime group is syn to the amide group, probably due to the formation of an intra­molecular N—H⋯N hydrogen bond that forms an S(6) ring motif. In the crystal, mol­ecules are linked by pairs of bifurcated O—H⋯(O,N) hydrogen bonds, forming inversion dimers. The latter are linked via C—H⋯O and C—H⋯N hydrogen bonds, forming sheets lying parallel to (502). The sheets are linked via π–π stacking inter­actions [inter-centroid distance = 3.7588 (9) Å], involving the pyridine rings of inversion-related mol­ecules, forming a three-dimensional structure.

2-[(Pyridin-2-yl)amino]pyridinium 2,4,6-trinitrophenolate

In the cation of the title salt, C₁₀H₁₀N₃⁺·C₆H₂N₃O₇⁻, the pyridine and pyridinium rings are linked by an intra­molecular N—H⋯N hydrogen bond and are approximately coplanar, with a dihedral angle between their planes of 4.24 (6)°. In the crystal, the cations and anions are linked through N—H⋯O hydrogen bonds, forming supra­molecular chains propagating along the c-axis direction. π–π stacking is observed between neighbouring chains, the centroid–centroid distances being 3.7638 (11) (between pyridinium rings) and 3.5331 (11) Å (between benzene rings).

Tetra-kis[bis-(pyridin-2-yl)amine-κN (2)](nitrato-κO)silver(I)

In the title complex, [Ag(NO₃)(C₁₀H₉N₃)₄], the nitrate ligand is found to be disordered over two sets of positions, with occupancy factors of 0.473 (5) and 0.527 (5). The Ag^I ion is located in a square-pyramidal coordination environment formed by four N atoms from four bis­(pyridin-2-yl)amine ligands and one O atom from a nitrate ligand. Weak inter­actions between the Ag^I ions and the nitrate anions acting in a monodentate mode [Ag⋯O = 2.791 (13) and 2.816 (9) Å for the major component of the nitrate ligand, and 2.865 (8) and 2.837 (8) Å for the minor component] link the complex mol­ecules into a chain along [001]. N—H⋯O hydrogen bonds are observed.

(2,2'-Bi-pyridine-κ(2) N,N')tetra-kis-(dimethyl sulfoxide-κO)copper(II) bis-(perchlorate)

The title compound, [Cu(C₂H₆OS)₄(C₁₀H₈N₂)](ClO₄)₂, contains a Cu^II ion with a distorted octa­hedral coordination environment, bonded by four O atoms of the monodentate dimethyl sulfoxide ligands and two N atoms of the bidentate chelating 2,2′-bi­pyridine ligand. The equatorial Cu—N and Cu—O bond lengths are in the range 1.979 (2)-1.998 (3) Å. The axial Cu—O bond distances are 2.365 (2) and 2.394 (2) Å. In the crystal, the complex cations and perchlorate anions are connected by numerous C—H⋯O hydrogen bonds, which leads to additional stabilization of the structure. The perchlorate anion is disordered over two sets of sites with a 0.716 (3):0.284 (3) occupancy ratio.

(3-Acetyl-4-methyl-1H-pyrazol-1-ide-5-carboxyl-ato)bis-(1,10-phenanthroline)nickel(II) 3.5-hydrate

The title compound, [Ni(C₇H₆N₂O₃)(C₁₂H₈N₂)₂]·3.5H₂O, crystallizes as a neutral mononuclear complex with 3.5 solvent water mol­ecules. One of the water mol­ecules lies on an inversion centre, so that its H atoms are disordered over two sites. The coordination environment of Ni^II has a slightly distorted octa­hedral geometry, which is formed by one O and five N atoms belonging to the N,O-chelating pyrazol-1-ide-5-carboxyl­ate and two N,N′-chelating phenanthroline mol­ecules. In the crystal, O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonds involving the solvent water mol­ecules and pyrazole-5-carboxyl­ate ligands form layers parallel to the ab plane. These layers are linked further via weak π–π inter­actions between two adjacent phenanthroline mol­ecules, with centroid-to-centroid distances in the range 3.886 (2)–4.018 (1) Å, together with C—H⋯π contacts, forming a three-dimensional network.

Dichloridobis[3-(4-chloro-phen-yl)-2,N,N-trimethyl-2,3-di-hydro-1,2,4-oxa-diazole-5-amine-κN (4)]platinum(II)-4-chloro-benzaldehyde (1/1)

In the title 1:1 co-crystal, [PtCl2(C11H14ClN3O)2]·C7H5ClO, the coordination polyhedron of the Pt(II) atom is slightly distorted square-planar with the chloride and 2,3-di-hydro-1,2,4-oxa-diazole ligands mutually trans, as the Pt atom lies on an inversion center. The 4-chloro-benzaldehyde mol-ecules are statistically disordered about an inversion centre with equal occupancies for the two positions. The Pt(II) complex forms a three-dimensional structure through C-H⋯Cl and weaker C-H⋯O inter-actions with the 4-chloro-benzaldehyde mol-ecule.

Dichloridobis[3-(4-meth-oxy-phen-yl)-2-methyl-5-(piperidin-1-yl)-2,3-di-hydro-1,2,4-oxa-diazole-κN (4)]platinum(II)

In title compound, [PtCl2(C15H21N3O2)2], the Pt(II) cation, located on an inversion center, is coordinated by two Cl(-) anions and two 3-(4-meth-oxy-phen-yl)-2-methyl-5-(piperidin-1-yl)-2,3-di-hydro-1,2,4-oxa-diazole ligands in a distorted Cl2N2 square-planar geometry. The di-hydro-oxa-diazole and piperidine rings display envelope (with the non-coordinating N atom as the flap atom) and chair conformations, respectively. In the crystal, weak C-H⋯Cl hydrogen bonds link the mol-ecules into supra-molecular chains running along the b axis. The piperidine ring is disordered over two positions with the occupancy ratio of 0.528 (4):0.472 (4).

Bis(2,2'-bipyridyl-κ(2) N,N')(sulfato-κ(2) O,O')nickel(II) 2.5-hydrate

The title compound, [Ni(SO₄)(C₁₀H₈N₂)₂]·2.5H₂O, is a nickel(II) complex with a distorted octa­hedral coordination geometry. The Ni^II atom is bonded by two O atoms of the bidentate chelating sulfate ligand and the four N atoms of two chelating 2,2′-bi­pyridine ligands. The Ni—N bond lengths range from 2.059 (3) to 2.075 (3) Å and the Ni—O bond lengths are 2.098 (3) and 2.123 (3) Å. The bipyridyl ligands are both close to planar (r.m.s. deviations of 0.254 and 0.0572 Å) and are almost orthogonal, making a dihedral angle of 82.77 (1)°. In the crystal, the complex and water mol­ecules are connected by O—H⋯O hydrogen bonds. Inter­estingly, six water mol­ecules form a chain linking two complex mol­ecules via sulfate O atoms. There are also stacking inter­actions between the aromatic rings of neighbouring 2,2′-bi­pyridine ligands with shortest non-covalent contacts of 3.268 (6), 3.393 (6) and 3.435 (5) Å. One of the three unique water molecules shows half-occupation.

A second monoclinic polymorph of 2-(3,5-dimethyl-1H-pyrazol-1-yl)-2-hy-droxy-imino-N'-[1-(pyridin-2-yl)ethyl-idene]acetohydrazide

The title compound, C14H16N6O2, is a second monoclinic polymorph of 2-[1-(3,5-dimeth-yl)pyrazol-yl]-2-hy-droxy-imino-N'-[1-(2-pyrid-yl)ethyl-idene] acetohydrazide, with two crystallographically independent mol-ecules per asymmetric unit. The non-planar mol-ecules are chemically equal having similar geometric parameters. The previously reported polymorph [Plutenko et al. (2012 ▶). Acta Cryst. E68, o3281] was described in space group Cc (Z = 4). The oxime group and the O atom of the amide group are anti with respect to the C-C bond. In the crystal, mol-ecules are connected by N-H⋯N hydrogen bonds into zigzag chains extending along the b axis.

Bis-{(E)-3-[2-(hy-droxy-imino)-propan-amido]-2,2-dimethyl-propan-1-aminium} bis[μ-(E)-N-(3-amino-2,2-dimethyl-prop-yl)-2-(hy-droxy-imino)-propanamido-(2-)]bis-{[(E)-N-(3-amino-2,2-dimethyl-prop-yl)-2-(hy-droxy-imino)-propanamide]-copper(II)} bis-((E)-{3-[2-(hy-droxy-imino)-propanamido]-2,2-dimethyl-prop-yl}carbamate) acetonitrile disolvate

The reaction between copper(II) nitrate and (E)-N-(3-amino-2,2-dimethyl­prop­yl)-2-(hy­droxy­imino)­propanamide led to the formation of the dinuclear centrosymmetric copper(II) title complex, (C₈H₁₈N₃O₂)₂[Cu₂(C₈H₁₅N₃O₂)₂(C₈H₁₇N₃O₂)₂](C₉H₁₆N₃O₄)₂·2CH₃CN, in which an inversion center is located at the midpoint of the Cu₂ unit in the center of the neutral [Cu₂(C₈H₁₅N₃O₂)₂(C₈H₁₇N₃O₂)₂] complex fragment. The Cu²⁺ ions are connected by two N—O bridging groups [Cu⋯Cu separation = 4.0608 (5) Å] while the Cu^II ions are five-coordinated in a square-pyramidal N₄O coordination environment. The complex mol­ecule co-crystallizes with two mol­ecules of acetonitrile, two mol­ecules of the protonated ligand (E)-3-[2-(hy­droxy­imino)­propanamido]-2,2-dimethyl­propan-1-aminium and two negatively charged (E)-{3-[2-(hy­droxy­imino)­propanamido]-2,2-dimethyl­prop­yl}carbamate anions, which were probably formed as a result of condensation between (E)-N-(3-amino-2,2-dimethyl­prop­yl)-2-(hy­droxy­imino)­propanamide and hydro­gencarbonate anions. In the crystal, the complex fragment [Cu₂(C₈H₁₅N₃O₂)₂(C₈H₁₇N₃O₂)₂] and the ion pair C₈H₁₈N₃O₂^+.C₉H₁₆N₃O₄⁻ are connected via an extended system of hydrogen bonds.

Diammine{N-[2-(hy-droxy-imino)-propion-yl]-N'-[2-(oxidoimino)-propion-yl]propane-1,3-diaminido-κ(4) N,N',N'',N'''}iron(III)

In the title compound, [Fe(C₉H₁₃N₄O₄)(NH₃)₂], the Fe^III atom, lying on a mirror plane, is coordinated by four N atoms of a triply deprotonated tetra­dentate N-[2-(hy­droxy­imino)­propion­yl]-N′-[2-(oxidoimino)­propion­yl]propane-1,3-diaminide ligand in the equatorial plane and two N atoms of two ammonia mol­ecules at the axial positions in a distorted octa­hedral geometry. A short intra­molecular O—H⋯O hydrogen bond between the cis-disposed oxime O atoms stabilizes the pseudo-macrocyclic configuration of the ligand. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds into a three-dimensional network. The ligand has a mirror-plane symmetry. One of the methyl­ene groups of the propane bridge is disordered over two sets of sites with equal occupancy factors.

Poly[μ-aqua-diaquabis-[μ-2-cyano-2-(oxidoimino)-acetato]-copper(II)dipotassium]

In the title compound, [CuK(2)(C(3)N(2)O(3))(2)(H(2)O)(3)](n), the Cu(2+) atom is in a distorted square-pyramidal coordination geometry. Two N atoms belonging to the oxime groups and two O atoms belonging to the carboxyl-ate groups of two trans-disposed doubly deprotonated residues of 2-cyano-2-(hy-droxy-imino)-acetic acid make up the basal plane and the apical position is occupied by the water mol-ecule. The neighboring Cu-containing moieties are linked into a three-dimensional framework by K-O and K-N contacts formed by two potassium cations with the carboxyl-ate and the oxime O atoms and the nitrile N atoms of the ligand. The environments of the K(+) cations are complemented to octa- and nona-coordinated, by K-O contacts with H(2)O mol-ecules. The crystal structure features O-H⋯O hydrogen bonds.

Poly[bis-[μ(4)-N-(2-hydroxy-imino-propion-yl)-N'-(2-oxidoimino-propion-yl)propane-1,3-diaminato]dimethano-lcalciumdicopper(II)]

In the title compound, [CaCu₂(C₉H₁₃N₄O₄)₂(CH₃OH)₂]_n, the Ca^II atom lies on an inversion center and is situated in a moderately distorted octa­hedral environment. The Cu^II atom is in a distorted square-pyramidal geometry, defined by four N atoms belonging to the amide and oxime groups of the triply deprotonated residue of N,N′-bis­(2-hydroxy­imino­propano­yl)propane-1,3-diamine (H₄pap) and one oxime O atom from a neighboring Hpap ligand at the apical site, forming a dimeric [Cu₂(Hpap)₂]²⁻ unit. Each dimeric unit connects four Ca atoms and each Ca atom links four [Cu₂(Hpap)₂]²⁻ units through Ca—O(amide) bonds, leading to a three-dimensional framework. The crystal structure involves intra- and inter­molecular O—H⋯O hydrogen bonds.

Unravelling the chemical nature of copper cuprizone

During the last 50 years, formation of the highly chromogenic copper cuprizone complex has been exploited for spectrophotometric determinations of copper although the precise chemical nature of the resulting species has never been ascertained; we eventually show here, in contrast to current opinion, that copper cuprizone is a copper(III)complex.