Oxalate Oxygen Atoms Research Articles

Structural characterization and anticancer studies of copper(II) and cobalt(III) complexes containing N,O-donor heterocyclic chelators

New Cu(II) and Co(III) complexes were synthesized from reaction of 3-((E)-1-(((E)-4-(diethylamino)-2-hydroxybenzylidene)hydrazono)ethyl)-8-methoxy-2H-chromen-2-one (HL) with Cu(NO3)2·3H2O and Co(NO3)2·6H2O in methanol. The synthesized compounds were characterized by various analytical and spectral (IR, UV-Vis, NMR, EPR, ESI-MS and HR-MS) techniques. From the spectral studies, we concluded that the formation of the ligand and complexes. In the copper complex with formula of [Cu2(L)(NO3)3(H2O)], HL coordinated to copper ion via azomethine nitrogen, lactone oxygen, azomethine nitrogen and oxalate oxygen atoms. In cobalt complex, the ligand coordinated to cobalt ion via ring carbonyl oxygen, azomethine nitrogen, oxalate oxygen and azomethine nitrogen, and the complex is of ML2 type with the general formula [CoL2]·2NO3. The cytotoxic nature of the compounds was analyzed with human liver cancer cells (HepG2) and human breast cancer cells (MM2), in which the complexes exhibited a comparable activity than the positive control cisplatin. The IC50 values of the compounds were greater than 200 μM for non-cancerous human umbilical vein endothelial (HUVEC) cells, indicating selectivity of the compounds towards cancer cells rather than normal cells. The apoptogenic natures of the complexes with HepG2 and MM2 cancer cells were confirmed using AO-EB and DAPI staining assays. These results revealed the possibility of developing highly active cobalt and copper complexes as anticancer agents.

Magnetic Switching in Vapochromic Oxalato-Bridged 2D Copper(II)-Pyrazole Compounds for Biogenic Amine Sensing

A new two-dimensional (2D) coordination polymer of the formula {Cu(ox)(4-Hmpz)·1/3H2O}n (1) (ox = oxalate and 4-Hmpz = 4-methyl-1H-pyrazole) has been prepared, and its structure has been determined by single-crystal X-ray diffraction. It consists of corrugated oxalato-bridged copper(II) neutral layers featuring two alternating bridging modes of the oxalate group within each layer, the symmetric bis-bidentate (μ-κ2O1,O2:κ2O2′,O1′) and the asymmetric bis(bidentate/monodentate) (μ4-κO1:κ2O1,O2:κO2′:κ2O2′,O1′) coordination modes. The three crystallographically independent six-coordinate copper(II) ions that occur in 1 have tetragonally elongated surroundings with three oxygen atoms from two oxalate ligands, a methylpyrazole-nitrogen defining the equatorial plane, and two other oxalate-oxygen atoms occupying the axial positions. The monodentate 4-Hmpz ligands alternatively extrude above and below each oxalate-bridged copper(II) layer, and the water molecules of crystallization are located between the layers. Compound 1 exhibits a fast and selective adsorption of methylamine vapors to afford the adsorbate of formula {Cu(ox)(4-Hmpz)·3MeNH2·1/3H2O}n (2), which is accompanied by a concomitant color change from cyan to deep blue. Compound 2 transforms into {Cu(ox)(4-Hmpz)·MeNH2·1/3H2O}n (3) under vacuum for three hours. The cryomagnetic study of 1–3 revealed a unique switching from strong (1) to weak (2 and 3) antiferromagnetic interactions. The external control of the optical and magnetic properties along this series of compounds might make them suitable candidates for switching optical and magnetic devices for chemical sensing.

Spontaneous enanti-omorphism in poly-phased alkaline salts of tris-(oxalato)ferrate(III): crystal structure of cubic NaRb5[Fe(C2O4)3]2.

We show here that the phenomenon of spontaneous resolution of enanti-omers occurs during the crystallization of the sodium and rubidium double salts of the transition metal complex tris-(oxalato)ferrate(III), namely sodium penta-rubidium bis-[tris-(oxalato)ferrate(III)], NaRb5[Fe(C2O4)3]2. One enanti-omer of the salt crystallizes in the cubic space group P4332 with Z = 4 and a Flack absolute structure parameter x = -0.01 (1) and its chiral counterpart in the space group P4132 with x = -0.00 (1). All metal ions are at crystallographic special positions: the iron(III) ion is on a threefold axis, coordinated by three oxalate dianions in a propeller-like conformation. One of the two independent rubidium ions is on a twofold axis in an eightfold coordination with neighbouring oxalate oxygen atoms, and the other one on a threefold axis in a sixfold RbO6 coordination. The sodium ion is at a site of D3 point group symmetry in a trigonal-anti-prismatic NaO6 coordination.

In Situ Encapsulation of Imidazolium Proton Carriers in Anionic Open Frameworks Leads the Way to Proton‐Conducting Materials

Three anionic open frameworks, formulated as [Him]2Eu2(ox)4(H2O)2·2H2O (1), [Him]2Tb2(ox)4(H2O)2·2H2O (2), and [Hmim]2Eu2(ox)4(H2O)2·2H2O (3; ox = oxalate, im = imidazole, mim = methylimidazole), have been synthesized by a solvent‐free method. In these solvent‐free processes, in situ encapsulation of imidazolium in the channels of the anionic open frameworks was successfully achieved. These compounds show 1D channels with extensive hydrogen‐bonding networks created between the guest molecules and adjacent oxalate oxygen atoms; the imidazolium or methylimidazolium cations are regularly arranged within the channels. Alternating current (AC) impedance measurements revealed that the three compounds display high proton conductivities (>10–3 S cm–1) at 298 K and 98 % relative humidity, with compound 2 showing the highest proton conductivity of 5.0 × 10–3 S cm–1 at 298 K. The high proton conductivities of compounds 1–3 may be attributed to the extensive hydrogen‐bonding networks existing in the open frameworks, which are constructed by water molecules, protonated imidazole or methylimidazole molecules, and adjacent oxalate oxygen atoms. This work provides an efficient synthetic strategy for the construction of high‐performance solid proton conductors.

Self-assembly of the tetrachlorido(oxalato)rhenate(iv) anion with protonated organic cations: X-ray structures and magnetic properties

Two novel ReIV compounds of formulae [H2bpy][ReIVCl4(ox)] (1) and [H3biim]2[ReIVCl4(ox)] (2) [H2bpy2+ = 4,4′-bipyridinium dication, H3biim+ = 2,2′-biimidazolium monocation, and ox2− = oxalate dianion] have been synthesised and magneto-structurally characterised. 1 crystallises in the monoclinic system with space group C2/c, and 2 crystallises in the triclinic system with space group P. The ReIV ion in 1 and 2 is six-coordinate, bonded to four chloride ions and two oxalate-oxygen atoms in a distorted octahedral geometry. Short intermolecular ReIV–Cl⋯Cl–ReIV contacts, Cl⋯π type interactions and hydrogen bonds are present in the crystal lattice of both compounds, generating novel supramolecular structures based on the highly anisotropic [ReIVCl4(ox)]2− species. Examination of the magnetic properties of 1 and 2 reveals significant antiferromagnetic coupling between ReIV ions propagated primarily through the ReIV–Cl⋯Cl–ReIV interactions, as evidenced by the occurrence of maxima in the magnetic susceptibility at ca. 12 (1) and 17 K (2).

Crystal structure of 2-methyl-1H-imidazol-3-ium aqua-tri-chlorido-(oxalato-κ(2) O,O')stannate(IV).

The tin(IV) atom in the complex anion of the title salt, (C4H7N2)[Sn(C2O4)Cl3(H2O)], is in a distorted octa-hedral coordination environment defined by three chlorido ligands, an oxygen atom from a water mol-ecule and two oxygen atoms from a chelating oxalate anion. The organic cation is linked through a bifurcated N-H⋯O hydrogen bond to the free oxygen atoms of the oxalate ligand of the complex [Sn(H2O)Cl3(C2O4)](-) anion. Neighbouring stannate(IV) anions are linked through O-H⋯O hydrogen bonds involving the water mol-ecule and the two non-coordinating oxalate oxygen atoms. In combination with additional N-H⋯Cl hydrogen bonds between cations and anions, a three-dimensional network is spanned.

An erbium-organic polymer incorporating 2-(hydroxyl)-6-methylisonicotinic and oxalate coligand with 63 topology

A new lanthanide-organic framework incorporating both substituted isonicotinic acid and oxalate coligand has been fabricated successfully through solvo-thermal reaction, namely, {[Er(μ2-H2Minca)](μ2-C2O4 · 2H2O] · 2H2O}n (I) (H3Minca = 2-(hydroxyl)-6-methyl-isonicotinic acid, H2C2O4 = oxalate acid). Complex I exhibits two dimensional (2D) corrugated networks with a 63 topology, in which {LnO8} polyhedron units are alternately linked through carboxylate and oxalate oxygen atoms into the 2D sheet layer (CIF file CCDC no. 948026). Thermogravimetric and different thermal analysis measurements indicate that I displays high thermal stability. Complex I also shows characteristic f-f transition luminescence emission in NIR region.

A Dimeric Copper(II) Complex of Oxalate and Oxamide Dioxime Ligands: Synthesis, Crystal Structure, Thermal Stability, and Magnetic Properties

The dimeric copper(II) complex [Cu(C2O4)(H2oxado)(H2O)]2 (1), where H2oxado=oxamide dioxime, has been synthesized in water and characterized by elemental and thermal analyses, IR spectroscopy, and single-crystal X-ray diffraction. Complex 1 is composed of two neutral [Cu(C2O4)(H2oxado)(H2O)] entities connected by Cu-O bonds between oxalate oxygen atoms and copper(II) ions, thereby producing a centrosymmetric dimer, with the Cu(II) centers exhibiting a strongly distorted octahedral coordination. Neighboring dimers are hydrogen-bonded through O- H···O interactions leading overall to a layer structure. Thermal analyses of complex 1 showed two significant weight losses corresponding to the coordinated water molecules, followed by the decomposition of the network. Variable-temperature (10 - 300 K) magnetic susceptibility measurements revealed very weak antiferromagnetic interactions (θ = 0:86 K from Curie-Weiss law behavior) within the dinuclear unit

Molecular and Crystal Structure Analysis of an Oxalate-Bridged Sodium 2D Polymer: [Na(μ<sub>1,1,2,3</sub>-Oxalato)(di-μ<sub>1,1</sub>-H<sub>2</sub>O)]<sub>N</sub>

The title compound, [Na(μ1,1,2,3-oxalato)(di-μbelongs to triclinic, space group P-1 with a = 5.6982 (11), b = 6.5040 (12), c = 6.6647 (13) Å, α = 75.040 (2), β = 84.990 (3), γ = 70.072 (3), V = 224.34 (7) Å3, C2H3NaO5, Mr = 130.03, Z = 2, Dc = 1.925 g/cm3, μ = 0.270 mm–1and F(000) = 132. Each sodium ions is located on crystallographic inversion symmetry centre and surrounded by six oxygen donors from three oxalate ligands and two di-μ1,1-waters in a distorted octahedron geometry. Two planar 4-member cyclβes crystallographic inversion are found in alternate repeated Na2O2subunit, which is further extended to two dimensional supermolecular fragment via μ1,1,2,3-oxalato-bridged. The crystal structure is aggregated to a 3D network through O-H…O hydrogen bonding involving the water molecules and oxalate oxygen atoms.

Low-Dimensional Copper(II) Complexes with the Trinucleating Ligand 2,4,6-Tris(di-2-pyridylamine)-1,3,5-triazine: Synthesis, Crystal Structures, and Magnetic Properties†

The preparation and structural characterization of three new copper(II) complexes of formula [Cu(3)(dipyatriz)(2)(H(2)O)(3)](ClO(4))(6) x 2 H(2)O (1), {[Cu(4)(dipyatriz)(2)(H(2)O)(2)(NO(3))(2)(ox)(2)](NO(3))(2) x 2 H(2)O}(n) (2), and [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](NO(3))(3) x 4 H(2)O (3) [dipyatriz = 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine and ox = oxalate] are reported. The structure of 1 consists of trinuclear units [Cu(3)(dipyatriz)(2)(H(2)O)(3)](6+) and uncoordinated perchlorate anions. The two dipyatriz molecules in 1 act as tris-bidentate ligands with the triazine cores being in a quasi eclipsed conformation. Each copper atom in 1 exhibits a distorted square pyramidal geometry CuN(4)O with four pyridyl-nitrogen atoms from two dipyatriz ligands building the basal plane and a water molecule occupying the axial position. The values of the intratrimer copper-copper separation are 8.0755(6) and 8.3598(8) A. Compound 2 exhibits a layered structure of copper(II) ions which are connected through bis-bidentate dipyatriz ligands and bidentate/outer monodentate oxalato groups. The copper atoms in 2 exhibit six- [Cu(1)N(4)O(2)] and five-coordination [Cu(2)N(2)O(3)]. A water molecule and three pyridyl-nitrogen atoms [Cu(1)] and two pyridyl-nitrogen plus two oxalate-oxygen atoms [Cu(2)] define the equatorial plane whereas either an oxalate-oxygen and a pyridyl-nitrogen [Cu(1)] or a nitrate-oxygen [Cu(2)] fill the axial positions. The copper-copper separation through the bridging oxalato is 5.6091(6) A whereas those across dipyatriz vary in the range 7.801(1)-9.079(1) A. The structure of compound 3 contains discrete cage-like hexacopper(II) units [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](3+) where two trinuclear [Cu(3)(dipyatriz)](6+) fragments are connected by three bis-bidentate oxalate ligands, the charge being balanced by three non-coordinated nitrate anions. The values of the intracage copper-copper distance are 5.112(3)-5.149(2) A (across oxalato) and 7.476(2)-8.098(2) A (through dipyatriz). Magnetic susceptibility measurements of polycrystalline samples of 1-3 in the temperature range 1.9-295 K show the occurrence of a weak antiferromagnetic interaction across dipyatriz in 1 [J = -0.08(1) cm(-1), the Hamiltonian being defined as (wedge)H = -J ((wedge)S(1).(wedge)S(2) + (wedge)S(1) x (wedge)S(3) + (wedge)S(2) x (wedge)S(3))] and weak ferro- (2) and strong antiferromagnetic (3) interactions through the oxalato bridge in 2 [J = +0.45(2) cm(-1)] and 3 [J = -390(1) cm(-1)]. The use of the dipyatriz-containing copper(II) species as a building block to design homo- and heterometallic magnetic compounds is analyzed and discussed.

Potassium aquaterbium(III) oxalate sulfate

Single crystals of KTb(C2O4)(SO4)(H2O), potassium aqua­terbium(III) oxalate sulfate, were obtained under hydro­thermal conditions. In the crystal structure, the Tb(III) atom is coordinated by four O atoms from two oxalate anions, three O atoms from three sulfate anions and one O atom from a water mol­ecule within a TbO8 distorted square antiprismatic coordination. The potassium and terbium(III) atoms are bridged by the oxalate and sulfate groups, forming a three-dimensional structure. The coordination mode of the oxalate has not yet been reported. O—H⋯O hydrogen bonding between the water molecules and the oxygen atoms of oxalate and sulfate anions is also observed.

Synthesis and structure of [UO2(C2O4){CONH2N(CH3)2}2

The single crystals of [UO2(C2O4){CONH2N(CH3)2}2] were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 7.461(2) A, b = 8.828(2) A, c = 11.756(2) A, β = 107.21(3)°, space group Pc, Z = 2, R = 2.94%. The structure comprises infinite chains [UO2(C2O4){CONH2N(CH3)2}2] extended along [001] and corresponding to the AT11M21 crystallochemical group (A = UO22+, T11 = C2O42−, M1 = N,N-CONH2N(CH3)2) of uranyl complexes. The chains are connected into a three-dimensional framework by hydrogen bonds involving the oxygen atoms of oxalate and uranyl ions and the N,N-dimethylcarbamide methyl groups.

Extended Tapes of Cyclic Water Hexamers in an Unusual Oxalate-Bridged One-Dimensional Copper(II) Complex

Extended tapes of cyclic water hexamers are formed in a one-dimensional copper(II) complex bridged by oxalate with a rare mono, bidentate coordination mode. The water tapes are stabilized by the hydrogen bond interactions between uncoordinated oxalate oxygen atoms and water molecules. Magnetic analysis reveals weak ferromagnetic interactions mediated by the oxalate bridge with the exchange parameter J = 0.36 cm-1.

Heterotrimetallic Oxalato-Bridged ReIV2MII Complexes (M = Mn, Co, Ni, Cu): Synthesis, Crystal Structure, and Magnetic Properties

The use of the (NBu4)2[ReIVCl4(ox)] mononuclear species as a ligand toward divalent first row transition metal ions in the presence of imidazole affords the new trinuclear compounds of formula (NBu4)2[{ReIVCl4(mu-ox)}2MII(Him)2] [NBu4+=tetra-n-butylammonium cation, ox=oxalate dianion, Him=imidazole; M=Mn (1), Co (2), Ni (3), Cu (4)] whose preparation, crystal structures, and magnetic properties are reported. 1-4 are isostructural complexes which are made up of discrete trinuclear [{ReIVCl4(mu-ox)}2MII(Him)2]2- anions and bulky NBu4+ cations. The Re and M atoms exhibit somewhat distorted octahedral surroundings which are built by four chloro and two oxalate oxygens (Re) and two imidazole nitrogen and four oxalate oxygen atoms (M), the central M atom being linked to the two peripheral Re atoms through bis-bidentate oxalate. The values of the Re...M separation across bridging oxalate vary in the range 5.646(2) (M=Ni) to 5.794(2) A (M=Mn). Magnetic susceptibility measurements on polycrystalline samples of 1-4 in the temperature range 1.9-300 K show the occurrence of significant intramolecular antiferro- (1) and ferromagnetic (2-4) interactions. The nature and magnitude of the magnetic coupling in 1-4 are qualitatively understood through orbital symmetry considerations.

Synthesis and structure of [Ce 2(H 2O) 3](C 2O 4) 2.5(H 3C 2O 3) and Ce 2(C 2O 4)(H 3C 2O 3) 4: The latter structure presents an interesting new framework, with 2-fold interpenetration

Single crystals of two cerium complexes, with mixed-ligands oxalate and glycolate, have been prepared in a closed system, at 200 °C for one month: [Ce 2(H 2O) 3](C 2O 4) 2.5(H 3C 2O 3) 1 and Ce 2(C 2O 4)(H 3C 2O 3) 4 2. 1 crystallizes in the orthorhombic system, space group Pbca, with a = 13.0090 ( 13 ) Å , b = 10.3870 ( 8 ) Å , and a = 22.102 ( 3 ) Å while 2 crystallizes in the tetragonal system, space group P4 2/ nbc, with a = 11.7030 ( 4 ) Å , c = 13.2570 ( 2 ) Å . For both complexes, the three-dimensional framework structure is built up by the linkages of the cerium and all the oxygen atoms of oxalate and glycolate ligands. For 2, its structure presents a nice case of two 3D identical sub-lattices, with 2-fold interpenetration. The only link between these two sub-lattices is assumed by strong hydrogen bonds between the hydroxyl function of the glycolate and the oxygen atoms of the oxalate. The schematized framework of 2, including only the cerium atoms, can be compared to that of cooperite (PtS). For 1, the two independent cerium have 9- or 10-fold coordination, forming a distorted monocapped or bicapped square antiprism polyhedron while for 2, the two independent cerium present 8-fold coordination, forming an almost regular dodecahedron. A quite relevant feature of 2 is the complete absence of water. 2 has been extended to other lanthanides ( Ln = Ce … Lu , yttrium included) leading to a family, which has been characterized by infra-red and thermal analysis.

Bis and tris(oxalato)ferrate(iii) complexes as precursors of polynuclear compounds

The preparation and crystal structure of two oxalato-bridged NaI–FeIII compounds, [Na3Fe(ox)3(H2O)4]·H2O (1) and [FeII(phen)3][NaFe(ox)3(H2O)3]·4H2O (5), two mononuclear FeIII complexes AsPh4[Fe(bipy)(ox)2]·H2O (3) and AsPh4[Fe(phen)(ox)2]·H2O (4) and an oxalato-bridged FeIII compound [AsPh4]4[Fe2(ox)5]·5H2O (2) (ox = oxalate dianion, bipy = 2,2′-bipyridine, phen = 1,10-phenantroline and AsPh4+ = tetraphenylarsonium cation) are reported here. The structure of 1 consists of infinite anionic [NaFe(ox)3]2− layers linked trough centrosymmetric [Na4(H2O)8]4+ tetranuclear units yielding a three-dimensional motif. Crystallization water molecules ensure the cohesion of the crystal lattice in 1. The iron environment is distorted octahedral being surrounded by six oxygen atoms of three oxalate groups, with an average iron to oxalate-oxygen bond distance of 2.012(3) A. There are four crystallographically independent sodium atoms, all of which have a highly distorted octahedral environment. Six oxalate-oxygen atoms are bound to Na(1) and Na(2), whereas the other two sodium atoms are surrounded by four water oxygen and two oxalate oxygen atoms [Na(3)] and three water oxygen and three oxalate oxygen atoms [Na(4)]. The structure of compound 2 consists of centrosymmetric dinuclear [Fe2(ox)5]4− anions, AsPh4+ cations and crystallization water molecules. The anionic unit contains two Fe(III) atoms, four bidentate and one bridging oxalato ligands. Each iron atom has a distorted octahedral environment. The structures of 3 and 4 consist of discrete [Fe(AA)(ox)2]− [AA = bipy (3) and phen (4)] anions, tetraphenylarsonium cations and uncoordinated water molecules which are linked by hydrogen bonds. Each iron atom is six-coordinated with two nitrogen atoms from the bidentate AA ligand and four oxalate-oxygen atoms building a distorted octahedral environment. The structure of compound 5 consists of anionic [Fe(ox)3Na(H2O)3]2− chains, tris-chelated low-spin iron(II) [Fe(phen)3]2+ units and lattice water molecules linked to the chains through hydrogen bonds in which the water molecules and oxygen atoms of the oxalate groups are involved. The chains contain Fe3+ and Na+ cations alternatively bridged by oxalate groups, the tris-chelated [Fe(ox)3]3− unit acting as a bidentate ligand through one oxalato group toward a central sodium atom. Magnetic susceptibilty measurements in the temperature range 2.0–290 K for 2 that reveal the occurrence of antiferromagnetic coupling (J = −6.5 cm−1, the Hamiltonian being defined as H = −JS1S2) between the high-spin iron(III) ions across the oxalato bridge.

Oxalato complexes of copper(II) with chelating diamines. Crystal structure of [Cu(dmen)ox(H 2O)] 2[Cu(dmen) 2](ClO 4) 2

Four new oxalato complexes of copper(II) of composition [Cu(dmen)ox(H 2O)] 2 [Cu(dmen) 2](ClO 4) 2 ( 1) (dmen= N, N-dimethylethylenediamine, H 2ox=oxalic acid), [(Cu(dmen)H 2O) 2ox](ClO 4) 2·H 2O ( 2), [Cu(tmen)(H 2O)(ox)Cu(aep)(H 2O)](ClO 4) 2 ( 3) (tmen= N, N, N′, N′-tetramethylethylenediamine, aep=2-(2-aminoethyl)pyridine) and [(Cu(dben)NO 3) 2ox] ( 4) (dben= N, N′-dibenzylethylenediamine) have been prepared and characterised by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dmen)ox(H 2O)] 2[Cu(dmen) 2](ClO 4) 2 ( 1) has been determined by single-crystal X-ray analysis. The structure of 1 contains a neutral [Cu(dmen)ox(H 2O)] complex, a cationic [Cu(dmen) 2] 2+ complex and perchlorate anions. The copper(II) atom of the neutral [Cu(dmen)ox(H 2O)] unit possesses a distorted square-pyramidal environment with two oxygen atoms of oxalate and two nitrogen atoms of dmen in the basal plane and an oxygen atom of a water molecule in the apical position. The copper(II) atom of the cationic [Cu(dmen) 2] unit shows a square-planar environment with four donor nitrogen atoms of two molecules of dmen. The temperature dependence of magnetic susceptibility for compounds 2– 4 was measured. Magnetochemical measurements show that copper(II) ions in compounds 2– 4 are antiferromagnetically coupled through the oxalate bridge, J=−157, −175 and −167 cm −1 ( H=−2 JS 1 S 2, S 1= S 2=1/2) for 2, 3 and 4, respectively.

One-dimensional oxalato-bridged copper(II) complexes with 3-hydroxypyridine and 2-amino-4-methylpyridine

Two new one-dimensional oxalato-bridged copper(II) compounds of formula [Cu(ox)L 2] n ( 1) and {[Cu 2(ox) 2L′ 3]·L′} n ( 2) [ox=oxalate dianion, L=3-hydroxypyridine (pyOH) and L′=2-amino-4-methylpyridine (ampy)] have been synthesized and characterized by FT-IR spectroscopy, variable-temperature magnetic measurements and single-crystal X-ray diffraction. The crystal structure of 1 comprises chains of copper atoms in which cis-[Cu(pyOH) 2] 2+ units are sequentially bridged by asymmetric bis-bidentate oxalato ligands with an intrachain copper–copper separation of 5.548(1) Å. Each copper atom is six-coordinated: four oxygen atoms belonging to two bridging oxalato ligands and two nitrogen atoms from two 3-hydroxypyridine ligands build a distorted octahedral environment around the metal atom. As in 1, the structure of compound 2 is made up of chains of copper atoms bridged sequentially by bis-bidentate oxalato ligands. Two types of copper(II) ion, one being six-coordinated (Cu(1)) and the other five-coordinated (Cu(2)), alternate regularly within the chain. The environment around Cu(1) is elongated octahedral with two cis-coordinated pyridine–nitrogen and two oxygen atoms from two oxalate ligands building the equatorial plane, the apical positions being filled by two oxalate-oxygen atoms. The environment around Cu(2) is distorted square pyramidal with four oxalato-oxygen atoms in the basal plane, and the pyridine nitrogen atom from one aromatic base in the apical position. Magnetic susceptibility data in the temperature range 2.0–300 K reveal regular ferromagnetic ( J=+1.3 cm −1) and alternating antiferromagnetic ( J=−66.6 cm −1, αJ=−58.6 cm −1) chain behaviours for 1 and 2. The nature and magnitude of the magnetic coupling through the oxalato bridge in 1 and 2 are analysed and discussed in the light of the available structural data.

Syntheses, crystal structures and magnetic properties of dinuclear copper(II) complexes with pyrazino[2,3-f ][4,7]phenanthroline (pap) as bridging ligand

Three dinuclear copper(II) complexes with pyrazino[2,3-f][4,7]phenanthroline (pap) as bridging ligand have been prepared; [Cu2(pap)(C2O4)2]·5H2O 1, [Cu2(pap)(H2O)7(SO4)]SO4·3H2O 2 and [Cu2(pap)(H2O)3(NO3)3]NO33. These are the first metal complexes of pap which have been characterized by X-ray crystallography and magnetic susceptibility measurements. In 1 the dinuclear complex is intercepted by a mirror plane; the bridging pap and the terminal oxalate ligands are bidentate in the equatorial plane of copper. In addition copper has weak axial interactions to oxygen atoms of oxalate in two neighbouring molecules. In 2 the two crystallograpically independent copper atoms are both six-co-ordinated with bridging pap and water molecules in equatorial positions, the axial positions being occupied by two water molecules or one water molecule and one sulfate oxygen atom, respectively. In 3 the co-ordination geometry of one copper is close to square pyramidal with pap, one nitrate oxygen atom and one water in equatorial positions; another water occupies the apical position. The description of the co-ordination sphere of the other copper is complicated by the presence of disorder in one of the co-ordinated nitrate groups. When considering only the major site of the disordered nitrate, the co-ordination geometry may in a first approximation be described as square pyramidal with a significant trigonal bipyramidal distortion. In the square pyramidal description the two pap nitrogen atoms, one water and one nitrate oxygen constitute the equatorial plane and a nitrate oxygen is situated in apical position. All the co-ordinated nitrate ions have a second weak Cu⋯O interaction. The Cu⋯Cu separations across bridging pap are 6.740 (1), 6.834 (2) and 6.808 A (3). Variable-temperature susceptibility measurements reveal Curie law behaviour with very weak intramolecular antiferromagnetic coupling in all three compounds, the relevant parameters being J = −1.4 cm−1, g = 2.06 for 1, J = −1.5 cm−1, g = 2.10 for 2, and J = −1.3 cm−1, g = 2.08 for 3 (the Hamiltonian being H = −J SA·SB).

A 3-dimensional 3-connected anionic polymeric network of a silver (I)-chromium(III) oxalato complex with tris-(2,2′-bipyridine)iron(II) cations

Abstract The crystal structure of [FeII(bpy)3]2+ n [AgCrIII(ox)3] n 2n−, where bpy = bipyridine, ox = Oxalate, C36H24AgCrFeN6O12, has been determined by X-ray diffraction at room temperature. Cubic crystals of tetrahedral shape have space group P213, a = 15.486(3) Å, Z = 4. The absolute structure, with respect to the crystal form {[unk]}, based on the four indexed crystal faces, was refined on F 2 by using a full-matrix procedure to final R = 0.050. The three-dimensional three-connected polymeric anionic silver(I)-chromium(III) tris-oxalate network consists of [AgI(ox)3] and [CrIII(ox)3] subunits. These subunits and the cationic complex [FeII(bpy)3]2+, which templates the structure, are all chiral and exhibit the Λ configuration. The chirality of the anionic decagon connected network corresponds to right-handed helicity. The cationic complexes fill the voids within the anionic network, and the iron(II) centers occupy sites with symmetry 3 at positions x, x, x (Wyckoff letter a). The Ag and Cr atoms occupy also special positions on three-fold rotation axes (Wyckoff letter a). The shortest distance between Ag and Cr in the three-dimensional network is 5.579(2) Å. There are only weak hydrogen bonding contacts of type C – H … O between the bpy ligands and the Oxalate oxygen atoms as acceptors. Overall, this structure represents a rare case of a chiral polymeric decagon framework type which has been accomplished because of the special coordination algorithm of the linking metal ions as well as of the choice of the bis-chelating ligands.