One-Pot Synthesis of a New Magnetically Coupled Heterometallic Cu2Mn2 [2 × 2] Molecular Grid

Tetranuclear MnII, CoII, CuII and ZnII grid complexes of an unsymmetrical ditopic ligand: synthesis, structure, redox and magnetic properties

Synthesis towards the preparation of an unsymmetrical binucleating Schiff-base ligand, (H₂L) is discussed. It has been synthesized by reacting methyl 6-(hydrazinecarbonyl)picolinate with 2-hydroxy acetophenone. The ligand (H₂L) comprises two different asymmetric binding pockets; however, when reacted with Mn(ii), Co(ii), Cu(ii) and Zn(ii) salts, very stable self-assembled [2 × 2] grid complexes form regardless of the employed metal-to-ligand ratio. The obtained complexes [Mn₄L₄]·(CH₃CN) (1), [Co₄L₄]·(CHCl₃) (2), [Cu₄L₄]·(CHCl₃) (3) and [Zn₄L₄] (4) have been fully characterized by physicochemical methods, including ESI mass spectrometry and X-ray crystallographic analyses, and their EPR, magnetic and redox properties are discussed. All discussed complexes self-assembled in a 'head-to-tail' fashion leading to [2 × 2] grid architectures. Mn, Co and Cu grid complexes show weak to moderate antiferromagnetic coupling among the four metal centers. The high stability of the grid structures is in line with the lack of any observable dissociation or exchange between metal ions in solution. Complexes 1 and 2 show four quasi-reversible to irreversible oxidative responses in cyclic voltammograms at a glassy carbon working electrode in 1,2-dichlorobenzene and at a platinum working electrode in dichloromethane, respectively.

Crystal structure and Hirshfeld surface analysis of N,N'-bis-(3-tert-butyl-2-hy-droxy-5-methyl-benzyl-idene)ethane-1,2-di-amine

The title compound, C26H36N2O2, crystallizes in the phenol-imine form. In the mol-ecule, there are intra-molecular O-H⋯N hydrogen bonds forming S(6) ring motifs, and the two aromatic rings are inclined to each other by 37.9 (7)°. In the crystal, mol-ecules are linked by pairs of weak C-H⋯O hydrogen bonds, forming inversion dimers. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (77.5%), H⋯C/C⋯H (16%), H⋯O/O⋯H (3.1%) and H⋯N/N⋯H (1.7%) inter-actions.

Details make the difference: a family of tetranuclear CuIIMnIII complexes with cube-like and double open cube-like cores

The "direct synthesis" approach, namely one-pot reaction of metal powders and ammonium salt with a methanol solution of a polydentate Schiff base (H₂L) formed in situ from salicylaldehyde and ethanolamine, has been successfully used for the preparation of the new heterometallic compounds [Cu₃Mn(L)₄(CH₃OH)₃]I₃ (1), [Cu₃Mn(L)₄(CH₃OH)₃(H₂O)]NCS·H₂O (2), [Cu₃Mn(L)₄(CH₃OH)(H₂O)_2.55]Br·0.45H₂O (3) and [Cu₃Mn(L)₄(H₂O)_3.4]BF₄·0.6H₂O (4). Crystallographic analysis revealed that 1-4 are based on the tetranuclear core {CuMn^III(μ₃-O)₄} where the metal centres are joined by the oxygen bridges of Schiff base ligands forming a cube-like arrangement. The novel heterometallic compound [Cu₃Mn(L)₄(CH₃OH)₃]₂[Mn(NCS)₄]·2CH₃OH (5) has been obtained by the "building block" approach using the reaction of [Cu(HL)₂] with manganese acetate and NH₄NCS in methanol. The crystal structure of 5 revealed the {CuMn^III(μ-O)₂(μ₃-O)₂} metal core which can be viewed as a double open cube. In spite of a similar {Cu₃MnO₄} atom set in the cores of 1-5, the complexes show rather different molecular structures and significantly differ by the number and combinations of coordinated CH₃OH/H₂O solvent molecules. Variable-temperature (2-300 K) magnetic susceptibility along with variable-field magnetization measurements of 1-5 showed a decrease of the effective magnetic moment value at low temperature, indicative of the antiferromagnetic coupling of medium size (-55 to -22 cm^-1). For these systems resembling a compressed prism the coupling constant in walls J₄ correlates with the averaged bonding angles in walls α: J₄vs. α develops approximately according to a straight line.

Palladium(ii) mononuclear and palladium(ii)/ruthenium(ii) heterodinuclear complexes containing 2-quinolyl-substituted (pyridine-2-carbonyl)hydrazone

Two mononuclear Pd^II complexes and a heterodinuclear Pd^II/Ru^II complex bearing the hydrazone-derived ligand were prepared and their structures and properties were characterized.

(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.

[Di-aqua-sesqui(nitrato-κO)hemi(perchlorato-κO)copper(II)]-μ-{bis-[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide}-[tri-aqua-(perchlorato-κO)copper(II)] nitrate monohydrate

In the binuclear title complex, [Cu2(ClO4)1.5(NO3)1.5(C18H16N6Se)(H2O)5]NO3·H2O, both Cu(II) ions are hexa-coordinated by O and N atoms, thus forming axially elongated CuO4N2 octa-hedra. The equatorial plane of each octa-hedron is formed by one chelating pyrazole-pyridine fragment of the organic ligand and two water mol-ecules. The axial positions in one octa-hedron are occupied by a water mol-ecule and a monodentately coordinated perchlorate anion, while those in the other are occupied by a nitrate anion and a disordered perchlorate/nitrate anion with equal site occupancy. The pyrazole-pyridine units of the organic selenide are trans-oriented to each other with a C-Se-C angle of 96.01 (14)°. In the crystal, uncoordinated nitrate anions and the coordinating water mol-ecules are involved in O-H⋯O and N-H⋯O hydrogen bonds, forming a bridge between the pyrazole group and the coordinating water mol-ecules. Further O-H⋯O hydrogen bonds between the complex mol-ecules and a π-π stacking inter-action with a centroid-centroid distance of 3.834 (4) Å are also observed.

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.

Pyridinium bis-(pyridine-κN)tetra-kis-(thio-cyanato-κN)ferrate(III)

In the title compound, (C₅H₆N)[Fe(NCS)₄(C₅H₅N)₂], the Fe^III ion is coordinated by four thio­cyanate N atoms and two pyridine N atoms in a trans arrangement, forming an FeN₆ polyhedron with a slightly distorted octa­hedral geometry. Charge balance is achieved by one pyridinium cation bound to the complex anion via N—H⋯S hydrogen bonding. The asymmetric unit consists of one Fe^III cation, four thio­cyanate anions, two coordinated pyridine mol­ecules and one pyridinium cation. The structure exhibits π–π inter­actions between pyridine rings [centroid–centroid distances = 3.7267 (2), 3.7811 (2) and 3.8924 (2) Å]. The N atom and a neighboring C atom of the pyridinium cation are statistically disordered with an occupancy ratio of 0.58 (2):0.42 (2).

Pyridinium bis-(pyridine-κN)tetra-kis-(thio-cyanato-κN)ferrate(III)-pyrazine-2-carbo-nitrile-pyridine (1/4/1)

In the title compound, (C₅H₆N)[Fe(NCS)₄(C₅H₅N)₂]·4C₅H₃N₃·C₅H₅N, the Fe^III ion is located on an inversion centre and is six-coordinated by four N atoms of the thio­cyanate ligands and two pyridine N atoms in a trans arrangement, forming a slightly distorted octa­hedral geometry. A half-occupied H atom attached to a pyridinium cation forms an N—H⋯N hydrogen bond with a centrosymmetrically-related pyridine unit. Four pyrazine-2-carbo­nitrile mol­ecules crystallize per complex anion. In the crystal, π–π stacking inter­actions are present [centroid–centroid distances = 3.6220 (9), 3.6930 (9), 3.5532 (9), 3.5803 (9) and 3.5458 (8) Å].

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.

(3-Acetyl-5-carboxyl-ato-4-methyl-1H-pyrazol-1-ido-κ(2) N (1),O (5))aqua-[(pyridin-2-yl)methanamine-κ(2) N,N']copper(II)

In the title compound, [Cu(C₇H₆N₂O₃)(C₆H₈N₂)(H₂O)], the Cu^II ion is in a distorted square-pyramidal N₃O₂ environment formed by two bidentate chelating ligands in the equatorial coordination sites and one water mol­ecule in the apical direction. In the crystal, O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonds link the complex mol­ecules into a three-dimensional supra­molecular network.

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.

[Aqua-bis-(nitrato-κO)copper(II)]-μ-{bis-[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl]selenide}-[diaqua-(nitrato-κO)copper(II)] nitrate monohydrate

In the title binuclear complex, [Cu2(NO3)3(C18H16N6Se)(H2O)3]NO3·H2O, the Cu(II) ions are penta-coordinated in a tetra-gonal-pyramidal geometry. In both cases, the equatorial planes are formed by a chelating pyrazole-pyridine group, a water mol-ecule and a nitrate O atom, whereas the apical positions are occupied by a water mol-ecule for one Cu(II) ion and a nitrate O atom for the other. The organic selenide ligand adopts a trans configuration with respect to the C-Se-C plane. Numerous inter-molecular O-H⋯O and N-H⋯O hydrogen bonds between the coordinating and lattice water mol-ecules, nitrate anions and pyrazole groups are observed. π-π stacking inter-actions between the pyridine rings [averaged centroid-centroid distance = 3.652 (5) Å] are also present. The lattice water molecule is equally disordered over two sets of sites.

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.

Tris(2,2'-bipyridine-κ(2)N,N')cobalt(III) bis-[bis-(pyridine-2,6-dicarboxyl-ato-κ(3)O(2),N,O(6))cobaltate(III)] perchlorate dimethyl-formamide hemisolvate 1.3-hydrate

In the title compound, [Co(C(10)H(8)N(2))(3)][Co(C(7)H(3)NO(4))(2)](2)(ClO(4))·0.5C(3)H(7)NO·1.3H(2)O, the Co(III) atom in the complex cation is pseudoocta-hedrally coordinated by six N atoms of three chelating bipyridine ligands. The Co(III) atom in the complex anion is coordinated by two pyridine N atoms and four carboxyl-ate O atoms of two doubly deprotonated pyridine-2,6-dicarboxyl-ate ligands in a distorted octa-hedral geometry. One dimethyl-formamide solvent mol-ecule and two water mol-ecules are half-occupied and one water mol-ecule is 0.3-occupied. O-H⋯O hydrogen bonds link the water mol-ecules, the perchlorate anions and the complex anions. π-π inter-actions between the pyridine rings of the complex anions are also observed [centroid-centroid distance = 3.804 (3) Å].

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.

fac-Tris(pyridine-2-carboxyl-ato-κN,O)cobalt(III)

In the title compound, [Co(C₆H₄NO₂)₃], the Co^III ion lies on a threefold rotation axis and is in a distorted octa­hedral environment defined by three N and three O donor atoms from three fac-disposed pyridine-2-carboxyl­ate ligands. The ligands are coordinated in a chelate fashion, forming three five-membered rings. In the crystal, translationally related complex molecules are organized into columns along [001] via C—H⋯O hydrogen bonds.

cis-Bis(2,2'-bipyridine-κN,N')bis-(dimethyl sulfoxide-κO)zinc bis-(tetra-phenyl-borate) dimethyl sulfoxide monosolvate

In the mononuclear title complex, [Zn(C₁₀H₈N₂)₂(C₂H₆OS)₂](C₂₄H₂₀B)₂·C₂H₆OS, the Zn^II ion is coordinated by four N atoms of two bidentate 2,2′-bipyridine mol­ecules and by the O atoms of two cis-disposed dimethyl sulfoxide mol­ecules in a distorted octa­hedral geometry. The S atom and the methyl groups of one of the coordinated dimethyl sulfoxide mol­ecules are disordered in a 0.509 (2):0.491 (2) ratio. The crystal packing is stabilized by C—H⋯O hydrogen bonds between the dimethyl sulfoxide solvent mol­ecules and tetra­phenyl­borate anions.

Poly[di-μ(2)-aqua-μ(5)-(pyridine-2,6-dicarboxyl-ato)-μ(3)-(pyridine-2,6-dicarboxyl-ato)-cobalt(II)disodium]

In the title compound, [CoNa₂(C₇H₃NO₄)₂(H₂O)₂]_n, the Co^II atom is coordinated by two pyridine N atoms and four carboxyl­ate O atoms from two doubly deprotonated pyridine-2,6-dicarboxyl­ate ligands in a distorted octa­hedral geometry. One Na⁺ cation is coordinated by three carboxyl­ate O atoms and two water mol­ecules and the other is coordinated by five carboxyl­ate O atoms and two water mol­ecules in an irregular geometry. The bis­(pyridine-2,6-dicarboxyl­ato)cobalt complex units are connected by Na⁺ cations and bridging water mol­ecules into a three-dimensional coordination network. O—H⋯O hydrogen bonds are formed between the water mol­ecules and the carboxyl­ate O atoms.

N'-(2-Hy-droxy-benzyl-idene)-2-(hy-droxy-imino)-propano-hydrazide

The mol­ecule of the title compound, C₁₀H₁₁N₃O₃, adopts an all-trans conformation and is approxomately planar, the largest deviation from the least-squares plane through all non-H atoms being 0.261 (1) Å. An intra­molecular O—H⋯N hydrogen bond occurs. In the crystal, the mol­ecules are packed into layers lying parallel to the ab plane by π-stacking inter­actions between the benzene ring of one molecule and the C—N bond of the oxime group of another molecule; the shortest inter­molecular C⋯C separation within the layer is 3.412 (1) Å. The layers are connected by O—H⋯O and N—H⋯O hydrogen bonds.

Diaqua-bis-(pyridine-2-carboxyl-ato-κN,O)manganese(II) dimethyl-formamide hemisolvate

There are two crystallographically independent complex mol-ecules with very similar geometries in the unit cell of the title compound, [Mn(C(6)H(4)NO(2))(2)(H(2)O)(2)]·0.5C(3)H(7)NO. The central ion is situated in a distorted octa-hedral environment of two N- and four O-donor atoms from two pyridine-2-carboxyl-ate ligands and two cis-disposed water mol-ecules. The carboxyl-ate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex mol-ecules are connected by O-H⋯O hydrogen bonds between the coordinated water mol-ecules and the uncoordinated carboxyl-ate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane.

1-{3-[1-(Hydroxyimino)ethyl]-4-methyl-1H-pyrazol-5-yl}ethanone

In the title compound, C(8)H(11)N(3)O(2), the oxime and the acetyl groups adopt a transoid conformation, while the pyrazole H atom is localized in the proximity of the acetyl group and is cis with respect to the acetyl O atom. In the crystal, dimers are formed as the result of hydrogen-bonding inter-actions involving the pyrazole NH group of one mol-ecule and the carbonyl O atom of another. The dimers are associated into sheets via O-H⋯N hydrogen bonds involving the oxime hydroxyl and the unprotonated pyrazole N atom, generating a macrocyclic motif with six mol-ecules.

3,5-Dimethyl-4-nitroso-1H-pyrazole

In the unit cell of the title compound, C(5)H(7)N(3)O, there are two conformers (A and B) which differ in the position of the oxime group with respect to the protonated pyrazole nitro-gen (trans in the A conformer and cis in the B conformer) and in the geometric parameters. The oxime group exists in the nitroso form in both conformers. In the crystal, mol-ecules are linked by inter-molecular N-H⋯O and N-H⋯N hydrogen bonds into zigzag-like chains along the b axis.

cyclo-Tetra-kis(μ-3-acetyl-4-methyl-1H-pyrazole-5-carboxyl-ato-κN,O:N,O)tetra-kis[aqua-copper(II)] tetra-deca-hydrate

The title compound, [Cu(4)(C(7)H(6)N(2)O(3))(4)(H(2)O)(4)]·14H(2)O, a tetra-nuclear [2 × 2] grid-type complex with S4 symmetry, contains four Cu(II) atoms which are bridged by four pyrazole-carboxyl-ate ligand anions and are additionally bonded to a water molecule. Each Cu(II) atom is coordinated by two O atoms of the carboxyl-ate and acetyl groups, two pyrazole N atoms of doubly deprotonated 3-acetyl-4-methyl-1H-pyrazole-5-carb-oxy-lic acid and one O atom of a water mol-ecule. The geometry at each Cu(II) atom is distorted square-pyramidal, with the two N and two O atoms in the equatorial plane and O atoms in the axial positions. O-H⋯O hydrogen-bonding interactions additionally stabilize the structure. One of the uncoordinated water molecules shows half-occupancy.

μ-Oxalato-bis[(2,2′-bipyridyl)copper(II)] bis(perchlorate) dimethylformamide disolvate monohydrate

The title compound, [Cu₂(C₂O₄)(C₁₀H₈N₂)₄](ClO₄)₂·2C₃H₇NO·H₂O, contains doubly charged centrosymmetric dinuclear oxalato-bridged copper(II) complex cations, perchlorate anions, and DMF and water solvate mol­ecules. In the complex cation, the oxalate ligand is coordinated in a bis-bidentate bridging mode to the Cu atoms. Each Cu atom has a distorted tetra­gonal-bipyramidal environment, being coordinated by two N atoms of the two chelating bipy ligands and two O atoms of the doubly deprotonated oxalate anion. Pairs of perchlorate anions and water mol­ecules are linked into recta­ngles by O—H⋯O bonds in which the perchlorate O atoms act as acceptors and the water mol­ecules as donors. Methyl groups of the DMF solvent molecule are disordered over two sites with occupancies of 0.453 (7):0.547 (7), and the water molecule is half-occupied.