Syntheses, structures and luminescence of a series of Cd(II)-containing coordination polymers constructed from a long flexible bis-triazole ligand

Six novel Cd(II) coordination polymers based on 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl (btmb), namely, [Cd(btmb)₂I₂]_n (1), [Cd(btmb)I₂]_n (2), {[Cd(btmb)₂(NO₃)₂]·H₂O}_n (3), {[Cd(btmb)₂(SCN)₂]·3H₂O}_n (4), {[Cd(btmb)(CH₃COO)₂(H₂O)]·CH₃CN}_n (5) and [Cd(btmb)Cl₂(H₂O)]_n (6) have been synthesized by the reactions of btmb with Cd(II) salts in the presence of different anions (I⁻, , NCS⁻, CH₃COO⁻ or Cl⁻) under appropriate reaction conditions. The assemblies of btmb with CdI₂ afford two different structures: two-dimensional (2D) rhombohedral grid layer network structure 1 and 2D layer structure 2 involved with one-dimensional (1D) linear cadmium chains. Treatment of btmb with Cd(NO₃)₂·4H₂O gives rise to a 2D grid network structure 3 which is similar to 1. When the I⁻ or NO₃⁻ anions were replaced by NCS⁻, CH₃COO⁻ or Cl⁻, different 1D coordination polymers 4-6 were obtained, respectively. Polymer 4 displays a 1D double-chain structure, while both polymers 5 and 6 show 1D zigzag chain structures. In addition, the luminescence measurements reveal that polymers 1-6 exhibit different fluorescent emissions in the solid-state at room temperature, which can be attributed to the various coordination environments of Cd(II), solvent molecules and different packing interactions in these polymers.     

Synthesis, characterization and properties of series coordination polymers constructed from a biphenyl dicarboxylate and nitrogen-containing mixed ligands

A series of coordination polymers have been prepared by the combination of flexible ligand 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂dpa) and different types of nitrogen-containing ligands, with various metal ions such as Co(II), Zn(II) and Cd(II). The single-crystal structure analyses reveal that the above complexes possess different structure features with the introduction of different nitrogen-containing ligands. When auxiliary linear ligand 4,4′-bipyridine (4,4′-bpy) is introduced, two-dimensional layered complex, [Co₂(dpa)₂(4,4′-bpy)₂(H₂O)]_n (1) is formed. Whereas if chelating ligand, 1,10-phenanthroline (1,10′-phen) and 2,2′-bipyridine (2,2′-bpy) are introduced, one-dimensional complex [Zn(dpa)(1,10′-phen)]_n (2) and discrete complexes [Co₂(dpa)₂(2,2′-bpy)₂(H₂O)₂] (3), [Co₃(dpa)₃(1,10′-phen)₆(H₂O)₂] (4), [Cd(dpa)(1,10′-phen)₂][(H₂dpa)₂(H₂O)₂] (5) are synthesized. To our interest, 1 and 2 crystallize in homochiral spacegroup. Furthermore, the magnetic property of complex 1 and the fluorescent properties of complexes 2 and 5 are studied.     

Extended structures of three new coordination polymers based on 1,10-phenanthroline derivatives and 1,4-benzenedicarboxylate mixed ligands: Preparation, structural characterization and properties

Three coordination polymers, namely, [Cd(HOIP)₂(1,4-bdc)] (1), [Cu(HOIP)(1,4-bdc)] (2) and [Cu(PDIP)(1,4-bdc)] (3) (HOIP = 2-(4-hydroxylbenzene) imidazo[4,5-f]1,10-phenanthroline, PDIP = 2-(3-pyridine) imidazo[4,5-f]1,10-phenanthroline, and 1,4-bdc = 1,4-benzenedicarboxylate), have been synthesized under the hydrothermal conditions. All complexes have been characterized by elemental analyses, IR and single-crystal X-ray diffraction. Structural analyses reveal that complex 1 possesses infinite one-dimensional (1D) chain bridged by 1,4-bdc ligands, complexes 2 and 3 both exhibit two-dimensional (2D) (4,4) network structures based on dinuclear [Cu₂O₂] units. However, the weak interactions are different in complexes 1-3. Moreover, the thermal properties of all complexes, fluorescence property of 1, and the electrochemical behavior of 3 are also reported in this paper.     

Cd(II) coordination polymers constructed from flexible disulfide ligand: Solvothermal syntheses, structures and luminescent properties

Four novel coordination polymers, [Cd(Hdtbb)(dtbb)_0.5(DMF)]_n (1), {[Cd(dtbb)(2,2′-bpy)(H₂O)]·2DMA}_n (2), {[Cd₂(dtbb)₂(1,4-bix)₂]·3DMF}_n (3) and [Cd(dtbb)(1,4-btx)]_n (4) [H₂dtbb = 2,2-dithiobisbenzoic acid, 2,2′-bpy = 2,2′-bipyridine, 1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, 1,4-btx = 1,4-bis(triazol-1-ylmethyl)benzene] have been synthesized and structurally characterized. Complexes 1 and 2 possess one-dimensional (1D) infinite structures. The structures of complexes 3 and 4 exhibit two dimensional (2D) frameworks, which mainly due to the differences in the bridging modes of dtbb²⁻ ligand and the effect of the N-donor auxiliary ligands. The infrared spectra, thermogravimetric and luminescent properties were also investigated for these compounds.     

Hydrothermal syntheses, structural characterizations and magnetic properties of cobalt(II) and manganese(II) coordination polymeric complexes containing pyrazinecarboxylate ligand

Two novel coordination polymeric complexes [Co(pzca)₂(H₂O)]_n (1) and [Mn(pzca)₂]_n (2) (pzca=2-pyrazinecarboxylate) have been synthesized by hydrothermal reaction of M(CH₃COO)₂·4H₂O (M=Co, Mn) and 2-pyrazinecarboxylic acid. The complex 1 displays an infinite zigzag chain structure in which each cobalt(II) center was coordinated by three nitrogen and three oxygen atoms to generate a CoN₃O₃ octahedral geometry. The existence of hydrogen bond leads to the formation of the interpenetrating stacking structure. Complex 2 indicates a two-dimensional layer structure through the linkage of bridging oxygen atom of pzca ligand. Each Mn(II) center exhibits a distorted octahedral coordination environment with four oxygen atoms and two nitrogen atoms. The distances of adjacent Mn(II) atoms are 3.503 and 5.654 Å, respectively. The magnetic property analyses reveal that both complexes show weak antiferromagnetic exchange interactions between the metal centers.     

A new family of lanthanide terpyridine nitrate complexes: Solvothermal syntheses, crystal structures and luminescent properties of [Ln(pytpy)(NO3)2(μ-OCH3)]2

The complexes [Ln(pytpy)(NO₃)₂(μ-OCH₃)]₂ (Ln = Eu(III), Tb(III), Dy(III), pytpy=4′-(n-pyridyl)-2,2′:6′,2″-terpyridine, n = 2, 3) were synthesized and characterized by IR, elemental analyses, UV–Vis and luminescent spectroscopy. Three complexes crystallized in monoclinic system, P2₁/n space group. Lanthanide ions are nine-coordinated by three nitrogen atoms from tridentate pytpy ligands, four oxygen atoms from two bidentate nitrate groups and two oxygen atoms from two methoxo groups, forming distorted tricapped trigonal prismatic geometries. The dimethoxo-bridges connect two metal ions in asymmetric fashion into dimeric structures with short LnLn distances of 3.767(1), 3.740(1) and 3.720(1) Å for Eu(III), Tb(III) and Dy(III) complexes, respectively. Photoluminescence measurement indicates that 1 and 3 emit the characteristic luminescence of Tb(III) and Eu(III) ions in the solid state, respectively. The luminescent spectrum of Eu(III) complex in solvents was also investigated.     

Synthesis and characterization of new coordination polymers generated from oxadiazole-containing ligands and IIB metal ions

The coordination chemistry of the oxadiazole-containing rigid bidentate ligands 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (L1) and 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L2) with inorganic IIB metal salts have been investigated. Five new coordination polymers (1-5) were prepared by solution reactions and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Cd(L1)₂(CH₃CN)₂](ClO₄)₂ · (CH₃CN)₂ (1) crystallized in the monoclinic space group P2₁/c, a = 8.4028(5) Å, b = 21.3726(13) Å, c = 10.5617(7) Å, β = 95.1200(10)°, and Z = 2. In the solid state, it adopts an infinite two-dimensional polymeric structural motif with effective cross section of ca. 14.31 × 14.31 Å. Cd(L2)(H₂O)(NO₃)₂ (2) crystallized in the monoclinic space group Ia, a = 7.1203(5) Å, b = 22.2475(15) Å, c = 20.2652(16) Å, β = 90.6080(10)°, and Z = 8. In the solid state, the two Cd(II) centers are connected to each other by L2 ligands and bridging nitrates into a two-dimensional network. [ZnCl₂(L1)] (3) and [HgI₂(L1)] · CH₃CN (4) crystallized in the monoclinic crystal system (3: P2₁/c, a = 5.3702(3) Å, b = 20.4800(11) Å, c = 12.4093(7) Å, β = 94.7930(10)°, and Z = 4; 4: P2/n, a = 17.2733(11) Å, b = 5.2173(3) Å, c = 20.4069(13) Å, β = 102.8690(10)°, and Z = 4). In the solid state, Zn(II) and Hg(II) metal centers are connected to each other by L1 ligands into a zigzag chain motif. Compound 5 (HgBr₂(L2) is different from 3 and 4, monoclinic, P2(1)/n, a = 5.470(4) Å, b = 16.271(13) Å, c = 16.486(12) Å, β = 93.197(15)°, and Z = 4) adopts a novel one-dimensional helical chain motif which resulted from the relative different coordinated orientation of the two N-donors on L2 ligand.     

Organocyanide coordination chemistry: Syntheses, structural characterisations and magnetic properties of copper (II) complexes with a di-imine/pyridine ligand

The reactions between the copper (II) salts [CuXL]PF₆ (L: 2,6-[1-(2,6-diisopropylphenylimino)ethyl]pyridine) (X = Cl 1, X = Br 2) and LiTCNQ, in a DMF/water mixture, or Et₃NH(TCNQ)₂, in acetone, produced the new complexes [CuXL(TCNQ)] (X = Cl 3, X = Br 4). For both compounds, crystallographic studies have clearly evidenced the existence of dimeric complexes [{CuClL}(TCNQ)]₂ owing to π-π overlap between two adjacent TCNQ⁻ radical anions. Compound 1 reacted with Et₄N(C₁₀N₇) to afford the mononuclear derivative [CuClL(C₁₀N₇)] (5), while its reaction with K₂C₁₀N₆ produced the dinuclear complex [(CuClL)₂(C₁₀N₆)] (6). The crystal structures of complexes 5 and 6 have been determined by X-ray crystallography. Magnetic studies have revealed that compound 6 displays weak antiferromagnetic interactions between the two metal centres, conversely compounds 3 and 5 exhibit purely paramagnetic behaviours.     

Hydrothermal synthesis, crystal structure and magnetic characterization of two 4f-3d heterometallic coordination polymers

Two new 4f-3d heterometallic coordination polymers [Gd₂Co(L₁)₃(ox)(H₂O)₄]·2.5H₂O (1, L₁ = pyridine-2,5-dicarboxylate anion, ox = oxalate dianion) and [GdNi(L₂)₂(ox)_0.5(H₂O)₃]·3H₂O (2, L₂ = pyridine-2,3-dicarboxylate anion) were successfully synthesized under hydrothermal conditions. In compound 1, one dimensional heterometallic and lanthanide infinite sheets were constructed with sole L₁ spacers and L₁-ox mixed bridges, respectively. While similar one dimensional heterometallic infinite sheet and normal lanthanide infinite zigzag chain were formed based on sole L₂ and L₂-ox mixed bridges, respectively in compound 2. Both of the two compounds exhibited new and interesting three dimensional topologies. In addition, the magnetic properties of the two compounds were analyzed via solid-state dc magnetic susceptibility measurements.     

Transition metal complexes with pyrazole based ligands, part 18: new binuclear Cu(I), Cu(II) and Co(II) complexes with 3,5-dimethyl-1-thiocarboxamide pyrazole: synthesis, structural and magnetic studies

Three new binuclear metal complexes of the formulas (L = 3,5-dimethyl-1-thiocarboxamide pyrazole) have been synthesized and characterized by chemical analysis, FT-IR spectroscopy, solution conductivity, solid state magnetic measurements and X-ray single crystal and variable temperature powder diffraction. Complex 1 forms doubly chloro-bridged dimers, with Cu(II) in distorted trigonal bipyramidal coordination with the apical positions occupied by chlorine atoms. Magnetic measurements indicate an antiferromagnetic interaction between the Cu(II) centres in the dimer, with the singlet-triplet exchange parameter of J = −19.40 cm⁻¹. Complex 2 forms doubly sulfur-bridged dimers, with Cu(I) in distorted tetrahedral coordination with apical positions occupied by bromine atoms. Complex 3 is a cobalt analogue of 1. It contains dinuclear units formed by five-coordinate high-spin Co(II) in a distorted trigonal bipyramidal environment. The magnetisation of 3 shows no significant departure from Curie-Weiss behaviour between room temperature and 5 K. All crystal structures are stabilized by two-dimensional hydrogen bonding networks between the carboxamide nitrogen donors and the terminal halide acceptors.     

Synthesis, structures, and magnetic properties of one-dimensional Fe-M (M = Ni, Cu) coordination polymers bridged by nitroprusside

Self-assembling [Fe(CN)₅(NO)]²⁻ and [M(L)]²⁺ (M = Ni, Cu; L = macrocycles) led to one-dimensional coordination polymers, [Ni(L1)][Fe(CN)₅(NO)] · 2H₂O (1) with parallel chains and [Cu(L2)][Fe(CN)₅(NO)] · 3H₂O (2) exhibiting a slanted chain structure. Compound 1 contains a planar macrocycle L1 coordinated to a slightly distorted octahedral Ni(II) ion in which the planarity of L1 gives rise to piling up chains in parallel. In contrast, a more flexible macrocyclic ligand L2 in 2 that surrounds a Cu center with a tetragonal elongation has bulky cyclohexyl groups together with pendant methyl side groups. The presence of the methyl groups on L2 in a chain makes the cyclohexyl groups in an adjacent chain tilted against the CuN₄ basal plane with the methyl groups, eventually resulting in the slanted chain structure. Magnetic data demonstrate that antiferromagnetic interactions (J ≈ −0.13 cm⁻¹) are operating although the paramagnetic centers are linked by the long diamagnetic [Fe(CN)₅(NO)]²⁻ anion.     

Comparative structural coordination chemistry of two tricyclic bisamidines

The tricyclic bisamidines L1 and L2 are designed to be preconstrained so as to present synperiplanar donor sites for metal coordination. Their very different bite angles of 35° and 70° result from the incorporation of two five-membered instead of six-membered rings in their respective backbones. Distinct coordination preferences in a variety of metal complexes have now been confirmed by X-ray structural studies. While L1 afforded monodentate, symmetrical and unsymmetrical chelating as well as bimetallic bridging modes in its complexes, L2 has been found exclusively in a bidentate chelating mode.     

Hydrothermal syntheses, structures and properties of five rare earth coordination polymers with (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid

Hydrothermal reactions of rare earth ions(III) with a flexible building unit (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid (H₂tzda) lead to five novel coordination polymers with 1D chain and 3D network structures, namely, {[Y₂(tzda)₃(H₂O)₁₀] · 5H₂O}_n (1) and [Ln₂(tzda)₃(H₂O)₅]_n [Ln = Er (2), Pr (3), Nd (4), Eu (5)]. Compound 1 has one-dimensional ribbon-like chain structure constructed by [Y₂(tzda)₃] units through the syn-anti bidentate bridging mode of carboxylate groups. Compounds 2-5 possess compact three-dimensional network structures which are made up of [Ln₂(tzda)₃] (Ln = Er, Pr, Nd and Eu) units bridged by carboxylate groups. In these compounds, the flexible tzda²⁻ ligand is versatile and displays six different coordination fashions to meet the requirement of the coordination preference of the metal center. Furthermore, the magnetic behaviors for 2-5 in the temperature range of 5.0-300 K and photoluminescent property of 5 are significantly investigated in this paper.     

Synthesis and structural characterization of dinuclear complexes of trivalent aluminum, gallium, indium and chromium derived from pyrazole-2-ethanol

The reaction of 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (HL) with anhydrous metal(III) halides (M = Al, Ga, In and Cr) results in the isolation of four novel dinuclear complexes [Al(μ-L)Cl₂]₂ (1), [Ga(μ-L)Cl₂]₂ (2), [In(μ-L)Br₂(H₂O)]₂·2thf (3) and [Cr(μ-L)Cl₂(H₂O)]₂·1.5thf (4) in good yields. The new complexes have been characterized with the aid of analytical and spectroscopic studies. A single crystal X-ray structure determination in each case confirms the dimeric structure for all the complexes in the solid-state. The pyrazole ethanol ligand binds to the metal through both pyrazole nitrogen and bridging alkoxide oxygen terminals with the formation of a central M₂O₂ core involving the ethoxide anion. The metal(III) center is pentacoordinated in compounds 1 and 2, while it is hexacoordinated in compounds 3 and 4.     

Solvothermal synthesis, crystal structure and magnetic property of a new dinuclear manganese(II)-azido complex: [Mn(2,2′-dpa)(N3)2]2 (2,2′-dpa = 2,2′-dipicolylamine)

A new dinuclear manganese(II)-azido complex: [Mn(2,2′-dpa)(N₃)₂]₂1 (2,2′-dpa = 2,2′-dipicolylamine) has been synthesized solvothermally. X-ray crystallography analysis reveals that it consists of two crystallographically independent dimeric manganese moieties; each manganese(II) atom is coordinated by one 2,2′-dipicolylamine, one terminal azido ligand, and double end-on bridging azido ligands, exhibiting a slightly distorted octahedral sphere. There are extensive short contacts among dimeric manganese moieties, which extend the structure into an interesting three-dimensional supramolecular array. Magnetic determination of 1 indicates that dominant ferromagnetic interaction and weak antiferromagnetic interaction, which are ascribed to the end-on azido bridges and the short contacts, respectively, co-exist in this complex.     

1D/2D coordination polymers of copper(II) having two superexchange pathways: syntheses, crystal structures and magnetic properties

Two new polynuclear complexes of Cu(II), [(μ-1,1,3-N₃)₂{Cu₂(me₂tn)₂(N₃)₂}]_n (1) (me₂tn=2,2-dimethylpropane-1,3-diamine) and [Cu₂(μ-C₂O₄)(μ-N₃)(ipr₂en)₂]_n(ClO₄)_n (2) (ipr₂en=N,N^′-di-isopropylethane-1,2-diamine) have been synthesized and structurally characterized by X-ray crystallography. The crystal structure of 1 displays a 2D network in which distorted octahedral copper(II) centers, chelated by a me₂tn ligand and bound to a terminal azide, are connected through μ-1,1,3 bridging azide anions. The structure of 2 shows 1D chains comprising alternating [(ipr₂en)Cu-Ox-Cu(ipr₂en)] units and end-to-end azide ligand. The chains on mutual H-bonding interaction through ClO₄⁻, give rise to a 2D supramolecular architecture. The magnetic data of complexes were recorded in the temperature range, 300-2 K. In case of complex 1, the magnetic data are consistent with a ferromagnetic interaction through the end-on azide bridge (J_FM=10 cm⁻¹) and a weak antiferromagnetic interaction (zj=−0.8 cm⁻¹) between the ferromagnetically coupled dimers and an average g-value of 2.05. The susceptibility data of 2 were fitted using an alternating AF-AF chain spin 1/2 law which leads to the following parameters J_oxalate=−180 cm⁻¹, J_azide=−43 cm⁻¹ and g=2.25 cm⁻¹.     

Syntheses, structures, and properties of novel one dimensional copper cyanide coordination polymers

Three new one-dimensional copper coordination polymers have been prepared and fully characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and magnetic susceptibility measurements. The structure of [Cu(CN)₂(bpy)] (1) (bpy = 2,2-bipyridyl) (monoclinic P2₁/c, a = 8.9761(7) Å, b = 16.731(1) Å, c = 8.0224(6) Å, β = 114.437(1)°) consists of Cu(II) metal centers coordinated by three cyanide ligands and chelated by one bpy to form the monomers Cu(CN)₃(bpy) with distorted square pyramidal geometry. Each monomer shares two cyanide ligands with two adjacent monomers to form infinite -Cu(II)-CN-Cu(II)-CN-Cu zigzag chains along the c-axis. The one-dimensional structure of [Cu(CN)(bpy)] (2) (hexagonal P3₂, a = 14.4883(6) Å, b = 12.921(1) Å) is built of tetrahedral Cu(CN)₂bpy metal complexes in which Cu(I) metal centers are coordinated by one nitrogen and one carbon from two different CN ligands, and two nitrogens from one bpy. The two CN ligands act as bridging ligands between adjacent monomers to form helical chains along the 3₂ screw axis. The crystal structure of [Cu₂Cl(CN)(bpy)] (3) (orthorhombic Pbca, a = 17.853(2) Å, b = 6.9724 (9) Å, c = 18.7357 (9) Å) consists of two monomers, CuCl₂(CN) and Cu(bpy)(CN) that share a cyanide ligand to form Cu₂Cl₂(CN)(bpy) dimers. The dimers link to each other by sharing Cl ligands leading to the formation of infinite Cu-Cl-Cu chain decorated by the complex Cu(CN)(bpy). Variable-temperature magnetic measurement shows an overall ferromagnetic behavior for compound 1. The magnetic pathway of compound 1 is through the cyanide bridge connecting apical and equatorial positions of adjacent copper (II) ions.     

Structural change of supramolecular coordination polymers of itaconic acid and 1,10-phenanthroline along lanthanide series

Five new supramolecular lanthanide coordination polymers with three different structures, {[La₂(IA)₃(phen)₂] · 2H₂O}_n (1), {[Ln(IA)_1.5(phen)] · xH₂O}_n [x = 1, Ln = Eu (2); x = 0.25, Ln = Dy (3)], and [Ln(IA)_1.5(phen)]_n [Ln = Er (4); Yb (5)], were prepared by hydro- and solvothermal reactions of lanthanide chlorides with itaconic acid (H₂IA) and 1,10-phenanthroline (phen), and structurally characterized by single crystal X-ray diffraction. 1 Comprises 1-D double-chains that are further assembled to a 3-D supramolecular structure via hydrogen bonds and π-π stacks between phen molecules. 2 and 3 have 2-D infinite networks which are further constructed to form 3-D supramolecular architectures with 1-D channels by π-π aromatic interactions. 4 and 5 have 2-D layer structures consisting of three types of rings which are further architectured to form 3-D supramolecular structures by C-H?O hydrogen bonds. The H₂IA ligands are all completely deprotonated and exhibit tetra-, penta-, and hexadentate coordination modes in the titled complexes. The high-resolution emission spectrum of 2 shows only one Eu³⁺ ion site in 2, which is in agreement with the result of X-ray diffraction. And the magnetic property and the thermal stability of 2 were also investigated.     

Syntheses, crystal structures and magnetic properties of 1D and 2D cobaltous coordination polymers with mixed ligands

Two new Co(II) coordination polymers with mixed ligands, {[Co(BTA)_0.5(DBI)₂]·DBI·H₂O}_n (1) and [Co(PDA)(DBI)(H₂O)]_n (2) (H₄BTA = benzene-1,2,4,5-tetracarboxylic acid; H₂PDA = 2,2′-(1,2-phenylene)diacetic acid; DBI = 5,6-dimethyl-1H-benzoimidazole) have been synthesized under hydrothermal conditions, respectively. Both of them are characterized by elemental analyses, powder X-ray diffraction, thermogravimetric analysis, single-crystal X-ray diffraction, and magnetic susceptibilities. In 1, the Co(II) ions are four-coordinated and lie in distorted tetrahedron coordination environment. 1D ladder-like chain structure is formed by the bridging BTA⁴⁻ ligand. In 2, the Co(II) ions are in slightly distorted octahedral coordination geometry, and linked by PDA²⁻ ligand exhibiting a 2D layer structure. Temperature-dependent magnetic susceptibility measurements of 1 and 2 revealed that there are antiferromagnetic interactions between Co(II) ions.     

Ferromagnetic interactions in copper(II) and nickel(II) coordination polymers containing nitronyl nitroxide radical and terephthalate

Two new complexes [Cu(NITmPy)₂(tp)] 1 and [Ni(NITmPy)₂(tp)(H₂O)₂] 2 (NITmPy=2-(3^′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and tp=terephthalato dianion) were synthesized and structurally and magnetically characterized. The structure of 1 is a neutral infinite chain where Cu(NITmPy)₂ units are linked by terephthalate ligands. In complex 2, the 1-D chains of Ni(NITmPy)₂ (H₂O)₂ units connected by tp develop into 2-D network via hydrogen bond interactions. The magnetic properties of 1 and 2 have been investigated in the temperature range 2-300 K. Both complexes exhibit ferromagnetic coupling and antiferromagnetic interactions dominate at low temperature. The magnetic behavior is discussed based on their structures.