Crystal Structures,Magnetic Properties and Catecholase‐Like Activities of μ‐Alkoxo‐μ‐Carboxylato Double Bridged Dinuclear and Tetranuclear Copper(II) Complexes

One μ‐alkoxo‐μ‐carboxylato bridged dinuclear copper(II) complex, [Cu₂(L¹)(μ‐C₆H₅CO₂)] ( 1 )(H₃L¹ = 1,3‐bis(salicylideneamino)‐2‐propanol)), and two μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear copper(II) complexes, [Cu₄(L¹)₂(μ‐C₈H₁₀O₄)(DMF)₂]·H₂O ( 2 ) and [Cu₄(L²)₂(μ‐C₅H₆O₄]·2H₂O·2CH₃CN ( 3 ) (H₃L² = 1,3‐bis(5‐bromo‐salicylideneamino)‐2‐propanol)) have been prepared and characterized. The single crystal X‐ray analysis shows that the structure of complex 1 is dimeric with two adjacent copper(II) atoms bridged by μ‐alkoxo‐μ‐carboxylato ligands where the Cu···Cu distances and Cu‐O(alkoxo)‐Cu angles are 3.5 11 Å and 132.8°, respectively. Complexes 2 and 3 consist of a μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear Cu(II) complex with mean Cu‐Cu distances and Cu‐O‐Cu angles of 3.092 Å and 104.2° for 2 and 3.486 Å and 129.9° for 3 , respectively. Magnetic measurements reveal that 1 is strong antiferromagnetically coupled with 2J =‐210 cm^?1 while 2 and 3 exhibit ferromagnetic coupling with 2J = 126 cm^?1 and 82 cm^?1 (averaged), respectively. The 2J values of 1–3 are correlated to dihedral angles and the Cu‐O‐Cu angles. Dependence of the pH at 25 °C on the reaction rate of oxidation of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to the corresponding quinone (3,5‐DTBQ) catalyzed by 1–3 was studied. Complexes 1–3 exhibit catecholase‐like active at above pH 8 and 25 °C for oxidation of 3,5‐di‐tert‐butylcatechol.     

Assembly of 1-D and decanuclear cage compounds from copper halide,cyclohexenephosphonic acid,and 3-(2-pyridyl)pyrazole

The reactions of cyclohexenephosphonic acid (C₆H₉PO₃H₂) and 3-(2-pyridyl)pyrazole (2-pyPzH) with copper(II) chloride and copper(II) bromide affords a 1-D compound [Cu(2-pyPz)Cl] (1) and a decanuclear [Cu₁₀(OH)₄(C₆H₉PO₃)₆(2-pyPz)₄] (2) cage complex. In 1, adjacent copper ions are bridged by two 2-pyPz ligands into dimers, which are further linked by Cl^? into a ladder-like chain. Compound 2 has a decanuclear cage structure, the overall cage can be viewed as composed of two Cu₄(OH)₂(2-pyPz)₂ wings that are bridged by a central Cu₂P₂O₆ rim. Variable-temperature magnetic susceptibility studies indicate that both compounds show antiferromagnetic interactions between copper centers.     

Synthesis,magnetic properties,DNA binding and cleavage activity of a new oxalato bridged copper(II) complex

A novel oxalato‐bridged copper(II) complex has been prepared and structurally characterized: [Cu(bpa)(μ‐C₂O₄)].H₂O (bpa = bis(2‐pyridylmethyl) amine). In the complex, the copper ion is linked in an unusual μ_1,2,3‐C₂O₄^2? bridging mode, generating one‐dimensional zigzag chain disposition. Variable‐temperature magnetic susceptibility studies (2–300 K) reveal a weak ferromagnetic coupling, J = 0.63 cm^?1, between the copper ions. The interaction of the complex with CT‐DNA has been studied using UV–visible absorption and emission spectral methods, and the binding constant of the complex with CT‐DNA is K_app = 9 × 10⁴ m ^?1, which indicates that the interaction of the complex with DNA is a moderate intercalative mode. Furthermore, the complex cleaves supercoiled plasmid DNA efficiently in the presence of hydrogen peroxide. The mechanistic investigations suggest that the hydroxyl radical and singlet oxygen are involved in the DNA degradation. Copyright © 2012 John Wiley & Sons, Ltd.     

Tracking the dissolution–recrystallization structural transformation (DRST) of copper(II) complexes: a combined crystallographic,mass spectrometric and DFT study

Methanol‐ and temperature‐induced dissolution–recrystallization structural transformation (DRST) was observed among two novel Cu^II complexes. This is first time that the combination of X‐ray crystallography, mass spectrometry and density functional theory (DFT) theoretical calculations has been used to describe the fragmentation and recombination of a mononuclear Cu^II complex at 60 °C in methanol to obtain a binuclear copper(II) complex. Combining time‐dependent high‐resolution electrospray mass spectrometry, we propose a possible mechanism for the conversion of bis(8‐methoxyquinoline‐κ²N,O)bis(thiocyanato‐κN)copper(II), [Cu(NCS)₂(C₁₀H₉NO)₂], Cu1 , to di‐μ‐methanolato‐κ⁴O:O‐bis[(8‐methoxyquinoline‐κ²N,O)(thiocyanato‐κN)copper(II)], [Cu₂(CH₃O)₂(NCS)₂(C₁₀H₉NO)₂], Cu2 , viz. [Cu(SCN)₂( L )₂] ( Cu1 ) → [Cu( L )₂] → [Cu( L )]/ L → [Cu₂(CH₃O)₂(NCS)₂( L )₂] ( Cu2 ). We screened the antitumour activities of L (8‐methoxyquinoline), Cu1 and Cu2 and found that the antiproliferative effect of Cu2 on some tumour cells was much greater than that of L and Cu1 .     

A cyano‐bridged dinuclear 4f–3d array

A cyano‐bridged bimetallic 4f–3d complex, tri­aqua‐1κ³O‐μ‐cyano‐1:2κ²N:C‐penta­cyano‐2κ⁵C‐tetrakis(2‐pyrrolidone‐1κO)­chromium(III)­dysprosium(III) dihydrate, [CrDy(C₄H₇NO)₄(CN)₆(H₂O)₃]·2H₂O, has been prepared and characterized by X‐ray crystallographic analysis. The structure consists of a neutral cyano‐bridged Dy–Cr dimer. A hydrogen‐bonded three‐dimensional architecture is formed through N—H?O, O—H?N and O—H?O hydrogen bonds.     

A Homochiral Metal‐Dipeptide Supramolecular Framework Including a Hydrogen‐bonded Guest Network of Water and Uncoordinated 4, 4′‐Bipyridine

Abstract. The self‐assembly of glycyl‐L ‐leucine, Cu(NO₃)₂ · 3H₂O and 4, 4′‐bipyridine resulted in the tetranuclear‐based metal‐dipeptide supramolecular framework [Cu₄(C₈H₁₄N₂O₃)₄(H₂O)₂(C₁₀H₈N₂)₂] · (C₁₀H₈N₂) · 13H₂O ( 1 ). In the structure, the 4, 4′‐bipyridine‐bridged tetranuclear complex of Cu^II‐glycyl‐L ‐leucine interacts with each other to form a 1D hydrogen‐bonded chain including uncoordinated 4, 4′‐bipyridine and an interesting water chain in different channels. Under similar reaction conditions, racemic glycyl‐D ,L ‐leucine gave rise to the centrosymmetric dinuclear complex [Cu₂(C₈H₁₄N₂O₃)₂(C₁₀H₈N₂)] · 2H₂O ( 2 ), which is linked into a 2D hydrogen‐bonded structure without 4, 4′‐bipyridine included.     

A 3d‐4f Complex Constructed by the Assembly of a Cationic Template, [Cu(en)2]2+, and a 3D Anionic Coordination Polymer, [Sm2(C2O4)3(C5O5)(H2O)2]2–

A three‐dimensional (3D) 3d‐4f complex, [Cu(en)₂][Sm₂(C₅O₅)(C₂O₄)₃(H₂O)₂] · 8H₂O ( 1 ) (en = ethylenediamine, C₅O₅^2– = dianion of 4,5‐dihydroxycyclopent‐4‐ene‐1,2,3‐trione), were prepared via the in‐situ ring‐opening oxidation reaction of croconate in the presence of the template‐directed complex, [Cu(en)₂]²⁺ cation. The structural characterization determined by X‐ray diffraction determination reveals that the 3D anionic coordination polymer of [Sm₂(C₂O₄)₃(C₅O₅)(H₂O)₂]^2– in 1 can be describe in terms of in‐plane 2D honeycomb‐like [Sm₂(C₂O₄)₃] layered frameworks bridged by oxalate with bis‐chelating mode, being mutually interlinked via the bridge of μ_1,2,3,4‐croconate ligands with bis‐chelating coordination mode to complete the 3D open framework, which gives rise to 1D channels with pore size of 14.023 × 11.893 Å (longest atom–atom contact distances) along the b axis. The structure‐directing complex, [Cu(en)₂]²⁺, and solvated water molecules are resided into these honeycomb‐type hexagonal channels. The thermal stability of 1 was further studied by TGA and in‐situ powder X‐ray diffraction measurement.     

catena‐Poly[[(2,2′‐diamino‐4,4′‐bithiazole){μ3‐cis‐N‐(2‐carboxylatophenyl)‐N′‐[3‐(dimethylamino)propyl]oxamidato(3−)}dicopper(II)] nitrate 0.6‐hydrate]

The title complex, {[Cu₂(C₁₄H₁₆N₃O₄)(C₆H₆N₄S₂)]NO₃·0.6H₂O}_n, is a one‐dimensional copper(II) coordination polymer bridged by cis‐oxamide and carboxylate groups. The asymmetric unit is composed of a dinuclear copper(II) cation, [Cu₂(dmapob)(dabt)]⁺ {dmapob is N‐(2‐carboxylatophenyl)‐N′‐[3‐(dimethylamino)propyl]oxamidate and dabt is 2,2′‐diamino‐4,4′‐bithiazole}, one nitrate anion and one partially occupied site for a solvent water molecule. The two Cu^II ions are located in square‐planar and square‐pyramidal coordination environments, respectively. The separations of the Cu atoms bridged by oxamide and carboxylate groups are 5.2053 (3) and 5.0971 (4) Å, respectively. The complex chains are linked by classical hydrogen bonds to form a layer and then assembled by π–π stacking interactions into a three‐dimensional network. The influence of the terminal ligand on the structure of the complex is discussed.     

A novel Na–O–Ni–O–Ni bridging complex of Cl‐HXTA,where Cl‐HXTA is 2,6‐bis{[bis­(carboxyl­ato­methyl)­amino]­methyl}‐4‐chloro­phenolate

In the structure of the title compound, hepta­aqua‐1κ³O,2κ²O,3κ²O‐(μ₃‐2,6‐bis{[bis­(carboxyl­ato­methyl)­amino]methyl}‐4‐chloro­phenolato‐1κO;2κ⁴O,O′,N,O¹;3κ⁴O¹N′,O′′,O′′′)dinickel(II)­sodium(I) pentahydrate, [NaNi₂(C₁₆H₁₄ClN₂O₉)(H₂O)₇]·5H₂O or [Ni₂(Cl‐HXTA)(H₂O)₄{Na(H₂O)₃}]·5H₂O, the trinuclear complex unit consists of two distorted NiNO₅ octahedra bridged by a phenolate O atom and an NaO₄ tetrahedron bridged to one of the Ni octahedra by a carboxylate O atom. There are four intramolecular hydrogen bonds forming four six‐membered rings in the complex and the complex mol­ecules are connected to each other by a very complicated hydrogen‐bond network.     

Cyclometallated compounds. XV.

The title complex, tetra‐μ‐acetato‐O:O′‐bis{[μ‐1,4‐bis(2‐­pyridyl­oxy)­phenyl­ene‐N,C²:N′,C⁶]dipalladium(II)} bis­(tri­chloro­methane) dihydrate, [Pd₄(C₁₆H₁₀N₂O₂)₂(C₂H₃O₂)₄]·2CHCl₃·2H₂O, the product of the reaction of 1,4‐bis(2‐pyridyl­oxy)­benzene with palladium acetate, is shown to be a tetranuclear, rather than a polymeric, species. It crystallizes about a centre of inversion and has two doubly cyclo­palladated ligands bridged by four acetate groups. The cyclo­palladated ligand is far from planar in the complex and has the central benzene rings π‐stacked. The chelate rings exist in shallow boat conformations.     

Dimeric copper(II) 3,3‐dimethyl­butyrate adducts with ethanol, 2‐methylpyridine, 3‐methylpyridine, 4‐methylpyridine and 3,3‐dimethylbutyric acid

In the crystals of the five title compounds, tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(ethanol‐O)dicopper(II)–ethanol (1/2), [Cu₂(C₆H₁₁O₂)₄(C₂H₆O)₂]·2C₂H₆O, (I), tetrakis(μ‐3,3‐dimethylbutyrato‐O:O′)bis(2‐methylpyridine‐N)di­copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (II), tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(3‐methylpyridine‐N)di‐copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (III), tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(4‐methylpyridine‐N)di‐copper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₇N)₂], (IV), and tetrakis‐(μ‐3,3‐dimethylbutyrato‐O:O′)bis(3,3‐dimethylbutyric acid‐O)dicopper(II), [Cu₂(C₆H₁₁O₂)₄(C₆H₁₂O₂)₂], (V), the di­nuclear Cu^II complexes all have centrosymmetric cage structures and (IV) has two independent molecules. The Cu?Cu separations are: (I) 2.602 (3) Å, (II) 2.666 (3) Å, (III) 2.640 (2) Å, (IV) 2.638 (4) Å and (V) 2.599 (1) Å.     

Cover Picture: Coordination Algorithms Control Molecular Architecture: [CuI4(L2)4]4+ Grid Complex Versus [MII2(L2)2X4]y+ Side‐By‐Side Complexes (M=Mn,Co, Ni,Zn; X=Solvent or Anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3] (Chem. Eur. J. 16/2003)

The cover picture shows how differing coordination algorithms control the molecular architecture of complexes of the pyridazine‐containing, two‐armed, acyclic Schiff base ligand L2 (left, prepared from one equivalent of 3,6‐diformylpyridazine and two equivalents of d‐anisidine). Two very different complexes of L2 self‐assemble from tetrahedral copper(I ) versus octahedral zinc(II ), nickel(II ), and cobalt(II ) controlled 1 : 1 reactions with L2. In both cases the metal ions are bridged by the pyridazine moieties in L2, but in the case of the tetrahedral copper(II ) the result is a tetrametallic [2×2] grid complex ([Cu^I₄(L2)⁴]⁴⁺: top right), whilst in the case of the octahedral metal(II ) ions dimetallic side‐by‐side complexes, [M^II₂(L2)²(X)₄]^y+ (M = Mn, Co, Ni, Zn; X = solvent or anion), are formed (bottom right). The cover image was kindly generated by M. Crawford (University of Otago) with Strata Studio Pro (Strata). More details are given by S. Brooker and co‐workers on p. 3772 ff.     

Synthesis,Structure and Magnetic Property of an “Adamantane” Type Tetranuclear Iron(III) Complex

A new tetranuclear complex [Fe₄ L ₂(μ‐O)₂(μ‐>OH)₂](ClO₄)₄·H₂O ( 1 ), (H L = N,N,N′,N′‐tetrakis‐[(2‐pyridyl)methyl]‐2‐hydroxypropane‐1,3‐diamine) has been synthesized and its crystal structure and magnetic properties are shown. X‐ray crystallography reveals that complex 1 contains a quadruply‐charged, tetranuclear iron(III) cation and four perchlorate anions. In 1 , the Fe₄O₆ core is composed of a tetrahedron of iron atoms bridged by six oxygen atoms (two oxo, two hydroxo, and two alkoxo groups from L ). This results in an adamantane‐type geometry with the iron atoms occupying the bridgehead positions. Susceptibility data of 1 indicate strong intramolecular antiferromagnetic coupling of high‐spin Fe^III atoms.     

Synthesis,crystal structures and characterizations of three new copper(II) complexes including anti‐inflammatory diclofenac

Three new diclofenac‐based copper(II) complexes, namely tetrakis{μ‐2‐[2‐(2,6‐dichloroanilino)phenyl]acetato‐κ²O:O′}bis(methanol‐κO)copper(II), [Cu₂(μ‐dicl)₄(CH₃OH)₂] ( 1 ), bis{2‐[2‐(2,6‐dichloroanilino)phenyl]acetato‐κ²O,O′}bis(1‐vinyl‐1H‐imidazole‐κN³)copper(II), [Cu(dicl)₂(vim)₂] ( 2 ), and bis{2‐[2‐(2,6‐dichloroanilino)phenyl]acetato‐κ²O,O′}bis(1H‐imidazole‐κN³)copper(II), [Cu(dicl)₂(im)₂] ( 3 ) [dicl is diclofenac (C₁₄H₁₀Cl₂NO₂), vim is 1‐vinylimidazole (C₅H₆N₂) and im is imidazole (C₃H₄N₂)], have been synthesized and characterized by elemental analysis, FT–IR spectroscopy, thermal analysis and single‐crystal X‐ray diffraction. X‐ray diffraction analysis shows that complex 1 consists of dimeric units in which the dicl ligand exhibits a bidentate syn,syn‐μ₂ coordination mode linking two copper(II) centres. Complexes 2 and 3 have mononuclear units with the general formula [Cu(dicl)₂L₂] (L is vim or im) in which the Cu^II ions are octahedrally coordinated by two L and two dicl chelating ligands. The L and dicl ligands both occupy the trans positions of the coordination octahedron. The different coordination modes of dicl in the title complexes were revealed by Fourier transform IR (FT–IR) spectroscopy. The spin matching between the copper(II) centres in the dimeric [Cu₂(μ‐dicl)₄(CH₃OH)₂] units was also confirmed by magnetic data to be lower than the spin‐only value and electron paramagnetic resonance (EPR) spectra. The thermal properties of the complexes were investigated by thermogravimetric (TG) and differential thermal analysis (DTA) techniques.     

Proton‐transfer compounds of isonipecotamide with the aromatic dicarboxylic acids 4‐nitrophthalic, 4,5‐dichlorophthalic, 5‐nitroisophthalic and terephthalic acid

The structures of the 1:1 proton‐transfer compounds of isonipecotamide (piperidine‐4‐carboxamide) with 4‐nitrophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4‐nitrobenzoate, C₆H₁₃N₂O₈⁺·C₈H₄O₆⁻, (I)], 4,5‐dichlorophthalic acid [4‐carbamoylpiperidinium 2‐carboxy‐4,5‐dichlorobenzoate, C₆H₁₃N₂O₈⁺·C₈H₃Cl₂O₄⁻, (II)] and 5‐nitroisophthalic acid [4‐carbamoylpiperidinium 3‐carboxy‐5‐nitrobenzoate, C₆H₁₃N₂O₈⁺·C₈H₄O₆⁻, (III)], as well as the 2:1 compound with terephthalic acid [bis(4‐carbamoylpiperidinium) benzene‐1,2‐dicarboxylate dihydrate, 2C₆H₁₃N₂O₈⁺·C₈H₄O₄²⁻·2H₂O, (IV)], have been determined at 200 K. All salts form hydrogen‐bonded structures, viz. one‐dimensional in (II) and three‐dimensional in (I), (III) and (IV). In (I) and (III), the centrosymmetric R₂²(8) cyclic amide–amide association is found, while in (IV) several different types of water‐bridged cyclic associations are present [graph sets R₄²(8), R₄³(10), R₄⁴(12), R₃³(18) and R₆⁴(22)]. The one‐dimensional structure of (I) features the common `planar' hydrogen 4,5‐dichlorophthalate anion, together with enlarged cyclic R₃³(13) and R₄³(17) associations. In the structures of (I) and (III), the presence of head‐to‐tail hydrogen phthalate chain substructures is found. In (IV), head‐to‐tail primary cation–anion associations are extended longitudinally into chains through the water‐bridged cation associations, and laterally by piperidinium–carboxylate N—H...O and water–carboxylate O—H...O hydrogen bonds. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen‐bonded structures. An additional example of cation–anion association with this cation is also shown in the asymmetric three‐centre piperidinium–carboxylate N—H...O,O′ interaction in the first‐reported structure of a 2:1 isonipecotamide–carboxylate salt.     

Structure and spectroscopic properties of the dimeric copper(I) N‐heterocyclic carbene complex [Cu2(CNCt‐Bu)2](PF6)2

In recent years, the use of copper N‐heterocyclic carbene (NHC) complexes has expanded to fields besides catalysis, namely medicinal chemistry and luminescence applications. In the latter case, multinuclear copper NHC compounds have attracted interest, however, the number of these complexes in the literature is still quite limited. Bis[μ‐1,3‐bis(3‐tert‐butylimidazolin‐2‐yliden‐1‐yl)pyridine]‐1κ⁴C²,N:N,C^2′;2κ⁴C²,N:N,C^2′‐dicopper(I) bis(hexafluoridophosphate), [Cu₂(C₁₉H₂₅N₅)₂](PF₆)₂, is a dimeric copper(I) complex bridged by two CNC, i.e. bis(N‐heterocyclic carbene)pyridine, ligands. Each Cu^I atom is almost linearly coordinated by two NHC ligands and interactions are observed between the pyridine N atoms and the metal centres, while no cuprophilic interactions were observed. Very strong absorption bands are evident in the UV–Vis spectrum at 236 and 274 nm, and an emission band is observed at 450 nm. The reported complex is a new example of a multinuclear copper NHC complex and a member of a compound class which has only rarely been reported.     

Magnetic Exchange Interactions in Dinuclear Copper(II) and Nickel(II) Complexes with μ‐Oxalato Bridges. The Structure of μ‐Oxalato(O,O′, O″, O‴)‐bis{[1, 8‐di(2‐pyridyl)‐3, 6‐dithiaoctane‐N,N′, S,S′]nickel(II)} Dinitrate Dihydrate

A copper(II) and two nickel(II) dinuclear oxalato‐bridged compounds of formulae [{Cu(bpdto)}₂(μ‐ox)](ClO₄)₂ ( 1 ), [{Ni(bpdto)]₂(μ‐ox)](ClO₄)₂( 2 ), and [{Ni(bpdto)}₂(μ‐ox)](NO₃)₂·2H₂O ( 3 ), where bpdto = 1, 8‐bis(2‐pyridyl)‐3, 6‐dithiaoctane and ox = oxalate = C₂O₄^2— anion, have been synthesized and characterized. The crystal structure of 3 was determined by single‐crystal X‐ray analysis. It is a dinuclear complex with i symmetry in which the oxalate ligand is coordinated in bis(didentate) fashion to the inversion centre‐related nickel atoms. The distorted octahedral environment of each nickel atom is completed by two sulphur atoms in the equatorial plane and by two pyridyl nitrogen atoms in axial positions. Magnetic susceptibility measurements over the range 5 — 299K, show antiferromagnetic interactions that are weak in 1 (J = —12.8 cm^—1) and strong in 2 and 3 (J = —37.8 and —40.9 cm^—1, respectively), which in the case of 3 is in keeping with the observed structural parameters.     

Hydrogen Bonds as Structural Directive towards Unusual Polynuclear Complexes: Synthesis,Structure, and Magnetic Properties of Copper(II) and Nickel(II) Complexes with a 2-Aminoglucose Ligand

The reaction of benzyl 2-amino-4,6-O-benzylidene-2-deoxy-α-D -glucopyranoside (HL) with the metal salts Cu(ClO₄)₂ ⋅ 6 H₂O and Ni(NO₃)₂ ⋅ 6 H₂O affords via self-assembly a tetranuclear μ₄-hydroxido bridged copper(II) complex [(μ₄-OH)Cu₄(L)₄(MeOH)₃(H₂O)](ClO₄)₃ ( 1 ) and a trinuclear alcoholate bridged nickel(II) complex [Ni₃(L)₅(HL)]NO₃ ( 2 ), respectively. Both complexes crystallize in the acentric space group P2₁. The X-ray crystal structure reveals the rare (μ₄-OH)Cu₄O₄ core for complex 1 which is μ₂-alcoholate bridged. The copper(II) ions possess a distorted square-pyramidal geometry with an [NO₄] donor set. The core is stabilized by hydrogen bonding between the coordinating amino group of the glucose backbone and the benzylidene protected oxygen atom O4 of a neighboring {Cu(L)} fragment as hydrogen-bond acceptor. For complex 2 an [N₄O₂] donor set is observed at the nickel(II) ions with a distorted octahedral geometry. The trinuclear isosceles Ni₃ core is bridged by μ₃-alcoholate O3 oxygen atoms of two glucose ligands. The two short edges are capped by μ₂-alcoholate O3 oxygen atoms of the two ligands coordinated at the nickel(II) ion at the vertex of these two edges. Along the elongated edge of the triangle a strong hydrogen bond (244 pm) between the O3 oxygen atoms of ligands coordinating at the two relevant nickel(II) ions is observed. The coordinating amino groups of the these two glucose ligands are involved in additional hydrogen bonds with O4 oxygen atoms of adjacent ligands further stabilizing the trinuclear core. The carbohydrate backbones in all cases adopt the stable ⁴C₁ chair conformation and exhibit the rare chitosan-like trans-2,3-chelation. Temperature dependent magnetic measurements indicate an overall antiferromagnetic behavior for complex 1 with J₁=−260 and J₂=−205 cm⁻¹ (g=2.122). Compound 2 is the first ferromagnetically coupled trinuclear nickel(II) complex with J_A=16.4 and J_B=11.0 cm⁻¹ (g_1,2=2.183, g₃=2.247). For the high-spin nickel(II) centers a zero-field splitting of D_1,2=3.7 cm⁻¹ and D₃=1.8 cm⁻¹ is observed. The S=3 ground state of complex 2 is consistent with magnetization measurements at low temperatures.     

[{Cu(phen)2}(μ‐malato){Cu(phen)(NO3)}](NO3)·4H2O: malate acting as a tetra­dentate and dibridging ligand in a dinuclear copper complex

The crystal structure of the title compound, μ‐2‐hydroxy­butane­dioato‐1κ²O⁴,O^4′:2κ³O¹,O²,O⁴‐nitrato‐2κO‐tris­(1,10‐phen­anthroline)‐1κ⁴N,N′;2κ²N,N′‐dicopper(II) nitrate tetra­hydrate, [Cu₂(C₄H₃O₅)(NO₃)(C₁₂H₈N₂)₃](NO₃)·4H₂O, contains an unsymmetrical dinuclear copper complex with Cu(phen)₂ and Cu(phen)(NO₃) moieties (phen is 1,10‐phenanthroline) bridged by a malate (2‐hydroxy­butane­dioate) ligand, which acts as a double‐bridging and tetra­dentate ligand. As a result of this double‐bridging action, especially the direct coordination of the O atom of one carboxyl­ate group of malate to the two Cu atoms, the Cu⋯Cu distance is only 4.199 (1) Å and the two phen planes are roughly parallel [the shortest inter­planar distance is 3.28 (1) Å], exhibiting an obvious intra­molecular π–π stacking inter­action.     

A New Mixed‐Valent Copper Cyanido Complex and a New Copper(II) Acetato Complex,Prepared with an Ionic Liquid

When copper(II) acetate is treated with the ionic liquid n‐butylmethylimidazolium cyanide (BMIm‐CN), in ethanol solution, two new copper coordination compounds are obtained. (BMIm)₂[Cu₄(CN)₇] comprises a 3D coordination polymer of cyanide bridged copper ions. This anionic coordination polymer contains Cu^I as well as Cu^II ions, i.e. it is a mixed‐valent compound. The polymer can be described as honeycomb structure with the BMIm⁺ cation being located in the cages. The second compound obtained from the chemical reaction is (BMIm)[Cu₂(OAc)₅][Cu(OAc)₂(H₂O)]₂ · C₂H₅OH, which can be described as double‐salt. The first unit (BMIm)[Cu₂(OAc)₅] contains paddle wheel copper(II) acetato moieties, which are bridged by additional acetato ligands and form infinite chains. The second part of the double salt is the neutral, [Cu(OAc)₂(H₂O)]₂ complex. These two parts as well as the co‐crystallized ethanol molecule are connected through a network of hydrogen bridges.