Bitriazole bridged manganese(II) framework with weak ferromagnet behavior

An asymmetric bridging ligand 3,4′-bi-1,2,4-triazole (Hbtr) was used for constructing transition metal coordination polymer, and yielding a manganese(II) compound [Mn(btr)₂]_n (1) with a unique three-dimensional (3D) framework. Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic space group Fdd2 and the structure is 3D (3, 6)-connected topological framework constructed from manganese ions and μ₃-btr ligands. The magnetic investigation for compound 1 shows that it is an antiferromagnetically coupled 3D array of high-spin manganese(II) ions with long-range ordering below T = 2.6 K, which is a weak ferromagnetic state due to spin-canting.     

A coordination pi-pi framework exhibits spontaneous magnetization

A pi-pi scaffolding framework that was assembled as a one-dimensional chain structure comprising alternating Delta- and Lambda-iron(II) chiral building units, [Fe(II)(Delta)Fe(II)(Lambda)(ox)2(phen)2]n, reveals spontaneous magnetization that gives rise to pronounced hysteresis loops below 10 K.     

A 2D coordination polymer with canted ferromagnetism constructed from ferromagnetic [Ni(II)Co(II)] nodes

A bimetallic coordination polymer, infinity (2)[{LNi (II)Co (II)}(dca) 2], has been constructed from heterobinuclear [Ni (II)Co (II)] nodes and dicyanamido spacers [L (2-) is the dianion of the Schiff base resulting from the 2:1 condensation of 3-methoxysalicyladehyde with 1,3-propanediamine; L (2-) = N, N'-propylenebis(3-methoxysalycilideneiminato)]. The intranode Co (II)-Ni (II) interaction was found to be ferromagnetic because of the orthogonality of the magnetic orbitals. Below 12 K, the onset of the canted ferromagnetic ordering is observed.     

An unusual 3D entangled Co(II) coordination polymer directed by ferromagnetic molecular building block

A fascinating 3D entangled metal-organic framework, namely, {[Co(2)(bcp)(2)]·3H(2)O}(n) (1), was obtained through the solvothermal generation of flexible and long dicarboxylate (bcp) and metal salt. The crystal structure contains a 1D metal chain with bcp ligands wrapped around it in a wavy line and features an unusual entangled topological net. Furthermore, the magnetic behavior of 1 was also studied and indicated the existence of ferromagnetic interaction and long-range ordering character.     

A novel molecular ladder structure of Cu(II)-Ba(II) coordination polymer exhibiting ferromagnetic coupling

A novel one-dimensional ladder-like Cu-Ba compound ([Ba(H2O)3(CuL)2] x 2H2O)n (H3L = Glycylglycine, N-[1-(2-hydroxyphenyl)propylidene]), has been synthesized and structurally characterized; it exhibits ferromagnetic interaction.     

A 1D Cu(II) coordination polymer exhibiting ferromagnetic interactions and a mononuclear Cu(II) complex of substituted pyrazole carboxylic acids: Synthesis, characterization and crystal structure

Reaction of 2 equiv. amount of copper(II) nitrate hexahydrate with 1 equiv. of 5-methyl-1-pyridin-2-yl-1H-pyrazole-3-carboxylic acid (PyPzCA) in presence of triethyl amine base afforded a 1D coordination polymeric compound [Cu₂(PyPzCA)₂(H₂O)₃(NO₃)]NO₃·H₂O (1). Whereas, the same reaction when repeated with 1-(4,6-dimethyl-pyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carboxylic acid (PymPzCA) instead of PyPzCA, a mononuclear compound [Cu(PymPzCA)]·2H₂O·NEt₃ (2) is formed. Both the complexes are crystallographically characterized. In 1, both the copper atoms (Cu1 and Cu2) have distorted square pyramidal geometry with N₂O₃ chromophore while, in 2, the central copper atom has a distorted trigonal bipyramidal geometry with N₄O chromophore. Complex 1, is a 1D coordination polymer where the metal centers being far apart and are involved in a weak ferromagnetic interaction which is quite unexpected.     

A chiral layered Co(II) coordination polymer with helical chains from achiral materials

A layered coordination polymer Co(PDC)(H2O)2.H2O containing two helical chains was synthesized, and the resultant crystals were not racemic as evidenced by the observation of strong signals in vibrational circular dichroism (VCD) spectra.     

N(II) oxide coordination to Co complexes with water-soluble porphyrin

Novel, water-soluble metalloporphyrin of zwitterionic type (Co complex with 5,10,15,20-tetra(4N-carboxymethylenepyridyl)porphyrin tetrabromide) was synthesized and its interaction with N(II) oxide was studied. IR and electronic absorption spectra were analyzed. Alcoholic solutions of this complex saturated with NO were found to contain all three types of coordinated ligands, i.e., NO, NO⁺, and NO^?.     

Monodentate N-coordination of a 1,2,3,5-dithiadiazolyl to Mn(II), Co(II) and Ni(II): A new coordination mode

The reaction of neutral radical ligand 4-(2′-cyanofuryl-5′)-1,2,3,5-dithiadiazolyl with a stoichiometric amount of bis(hexafluoroacetylacetonato)-manganese(II), -cobalt(II) or nickel(II) generates alternating metal-ligand chains in the solid state. The coordination mode of this ligand to the metal dication is unprecedented, providing the first evidence that the nitrogen atoms of a 1,2,3,5-dithiadiazolyl are capable of coordination to a metal dication in the absence of chelation.     

Unprecedented ferromagnetic interaction in an erbium(III)–copper(II) coordination polymer

Two 3D Ln(III)–Cu(II) coordination polymers [Er₂Cu₃(pydc)₆(H₂O)₆]_n (1) and [Tb₂Cu₃(pydc)₆(H₂O)₆]_n (2) were hydrothermally prepared from pyridine-2,4-dicarboxylic acid (H₂pydc) and characterized by single-crystal X-ray diffraction analysis. The magnetic studies show that an unexpected ferromagnetic interaction between metal centers exists in 1 while 2 behaves as an antiferromagnet.     

Sorption-desorption behavior of bispyrazolato-copper(II) 1D coordination polymers

A new polycrystalline vapochromic polymorph of the one-dimensional copper bispyrazolate polymer reversibly and selectively absorbs a number of small molecules; the crystal structures of the anhydrous and fully hydrated species, determined by powder diffraction methods, are markedly different despite their simple, fast, and reversible interconversion.     

4,2-Ribbon like ferromagnetic cyano-bridged Fe(III)2Ni(II) chains: a magneto-structural study

The low-spin iron(III) complex AsPh(4)[Fe(III)(bpy)(CN)(4)].CH(3)CN (1) [AsPh(4) = tetraphenylarsonium cation] and the heterobimetallic chains [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)].4H(2)O with L = bpy (2) and phen (3) [bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline] have been prepared and their structures determined by X-ray diffraction methods. The structure of 1 consists of mononuclear [Fe(bpy)(CN)(4)](-) anions, tetraphenylarsonium cations and acetonitrile molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of the bidentate bpy and four carbon atoms of four terminal cyanide groups building a distorted octahedral surrounding around the metal atom. 2 and 3 are isomorphous compounds whose structure is made up of neutral 4,2-ribbon like bimetallic chains of formula [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)] where the [Fe(III)(L)(CN)(4)](-) unit acts as a bis-monodentate bridging ligand toward the trans-diaquanickel(II) units through two of its four cyanide groups in cis positions. The chains exhibit two orientations in the unit cell and they interact with each other through hydrogen bonds involving the coordination and crystallization water molecules together with the uncoordinated cyanide nitrogen atoms of the [Fe(L)(CN)(4)](-) units. Compounds 2 and 3 behave as ferromagnetic Fe(III)(2)Ni(II) chains which interact ferromagnetically at very low temperatures in the case of 2, whereas metamagnetic-like behaviour is observed for with a critical field (H(c)) around 200 G. For H > H(c) the ferromagnetic Fe(III)(2)Ni(II) chains of 3 exhibit a frequency dependence of the out-of-phase ac susceptibility signal at T < 3.5 K.     

Self-assembly of a 1D heterotrimetallic Cu(II)-Sr(II)-Na(I) propeller-like chiral coordination polymer with ferromagnetic interactions

Self-assembly of metalloligand [CuL](-)(H(3)L =N-5-bromosalicylaldehydeglycyl-l-tyrosine) with Sr(2+) and Na(+) results in a 1D micro(2)-carboxylate- and H(2)O-bridged heterotrimetallic chiral coordination polymer [[Na(CuL)(3)Sr(H(2)O)(3)].9H(2)O]](n), which exhibits weak ferromagnetic exchange interactions and optical activity.     

Synthesis, crystal structure, and electron paramagnetic resonance investigations of heteronuclear Co(II)/Zn(II) and Co(II)/Cd(II) coordination polymers

The crystal structures of five new Co(II), Zn(II), and Cd(II) coordination polymers based on pyridine-substituted triazolyl carboxylates are reported. The two isomorphous compounds (∞)3[M(Me-3py-pba)?] (M = Zn, Co) possess {6?} topology (dia). In order to obtain heteronuclear compounds, we synthesized Co(II)-substituted Zn(II) and Cd(II) coordination polymers. At T = 5 K, the powder samples of the diamagnetically diluted Co(II)/Zn(II) and Co(II)/Cd(II) systems [Co/(Zn,Cd) ≈ 0.01] show intense electron paramagnetic resonance spectra, which were analyzed with an effective spin of S' = ?. The g tensor as well as the ??Co hyperfine tensor A(Co) are strongly anisotropic. The g tensor components are used to gain information about the symmetry of the Co(II) coordination sphere and covalency effects. Differential thermal analysis/thermogravimetry-mass spectrometry and temperature-dependent powder X-ray diffraction studies reveal high thermal stability of the three-dimensional coordination polymers up to 390 °C.     

Synthesis and characterization of Cu(II), Co(II) and Ni(II) coordination polymers containing bis(imidazolyl) ligands

Two structurally related flexible imidazolyl ligands, bis(N-imidazolyl)methane (L₁) and 1,4-bis(N-imidazolyl)butane (L₂), were reacted with Cu(II), Co(II) and Ni(II) salts of aliphatic/aromatic dicarboxylic acids resulting in the formation of a number of novel metal–organic coordination architectures, [CuB₂(ox)₂(L₁)₂(H₂O)₂] · 4H₂O (1) (ox = oxalate), [Cu(pdc)(L₂)_1.5] · 4H₂O (2, pdc = pyridine-2,6-dicarboxylate), [Co(L)₂(H₂O)₂](tp) · 4H₂O (3, tp = terephthalate), [Ni(L₁)₂(H₂O)₂](ip) · 5H₂O (4, ip = isophthalate), [Cu₂(L₁)₄(H₂O)₄](tp)₂ · 7H₂O (5), [Co(mal)(L₁)(H₂O)] · 0.5MeOH (6, mal = malonate), [Co(pdc)(L₁)(H₂O)] (7). All the complexes have been structurally characterized by X-ray diffraction analysis. The different coordination modes of the dicarboxylate anions, due to their chain length, rigidity and diimidazolyl functionality, lead to a wide range of different coordination structures. The coordination polymers exhibit 1D single chain, ladder, 2D sheet and 2D network structures. The aliphatic and aromatic dicarboxylates can adopt chelating μ₂ and chelating-bridging μ₃ coordination modes, or act as uncoordinated counter anions. The central metal ions are coordinated in N₂O₄, N₄O₂, N₂O₃ and N₃O₃ fashions, depending on the ancillary ligands. The topology of 1 gives rise to macrocycles which are connected through hydrogen bonds to form 1D chains, whereas compound 2 exhibits a 1D polymeric ladder in which the carboxylate acts as a pincer ligand. Compounds 3–5 show doubly bridged 1D chains, and the dicarboxylate groups are not coordinated but form 2D corrugated sheets with water molecules intercalated between the cationic layers. Compound 6 has a 2D network sheet structure in which each metal ion links three neighboring Co atoms by the bis(N-imidazolyl)methane ligand. The cobalt compound 7, with a 2D polymeric double sheet structure, is built from pincer carboxylate (pdc) and 1,4-bis(N-imidazolyl)methane ligands.     

A novel 3D energetic coordination polymer containing Co(II) atoms in a pentanuclear cluster

A novel coordination polymer [Co₅(OH)₂(dnbpdc)₄(H₂O)₆]·16H₂O (1) (dnbpdc = 6,6′-dinitro-4,4′-biphenyldicarboxylic acid) is obtained from a hydrothermal reaction. The structure of complex 1 is characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction analysis. The title compound (C₅₆H₇₀Co₅N₈O₅₆, M _r = 2045.85) crystallizes in the triclinic space group P-1 with a = 11.9349(2) Å, b = 12.1895(2) Å, c = 15.420(2) Å, α = 109.390(7)°, β = 94.786(1)°, γ = 108.027(9)°, V = 1968.4(4) ų, Z = 1, D _c = 1.726 g/cm³, F(000) = 1045, μ(MoK _α) = 1.154 mm^–1, T = 133(2) K, the final R = 0.0316 and wR = 0.0692 for 7032 observed reflections with I > 2σ(I). The coordination polymer is built of a pentanuclear Co(II) cluster, four dnbpdc ligands, two hydroxyl groups, six coordination water and sixteen crystal water molecules. Ligand oxygen atoms exhibit three types of coordination modes (monodentate, syn-syn bridging bidentate and bridging tridentate). Moreover, the infinite three-dimensional supramolecular network is generated by coordination and hydrogen bonds. The thermal stability of complex 1 is evaluated by differential scanning calorimetry and thermogravimetric analysis.     

A new mesitylenic cyclobutane substituted Schiff base ligand and its Co(II), Cu(II), Ni(II), and Zn(II) complexes

A new ligand, 4‐(1‐methyl‐1‐mesityl‐3‐cyclobutanyl)‐2‐(2‐hydroxy‐1‐naphthylideneimino)thiazole (LH), has been synthesized starting from 1‐methyl‐1‐mesityl‐3‐(2‐chloro‐1‐oxoethyl)cyclobutane and thiourea and subsequently 2‐hydroxy‐1‐napthalaldehyde. Mononuclear complexes with a metal‐ligand ratio of 1:2 have been prepared with Co(II), Cu(II), Ni(II), and Zn(II) metals. The authenticity of the ligand and its complexes are proposed based on elemental analyses, IR, UV‐vis, ¹³C and ¹H NMR spectra, magnetic susceptibility measurements, thermogravimetric analyses, and differential scanning calorimetry. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:42–46, 2001     

A novel hexanuclear mixed oxidation state Cu(II)(4)Cu(I)(2) cluster complex exhibiting weak ferromagnetic exchange

The complex [(PAH)(4)Cu(II)(4)Cu(I)(2)Br(10)] (1) (PAH = picolinamide hydrazone) containing a Cu(II)(4)Cu(I)(2) hexanuclear cluster, with two well-separated Cu(II)(2) dinuclear centers, results from a redox reaction involving a hydrolytically unstable ligand, salicilyl picolinamide hydrazone, and CuBr(2) in aqueous acetonitrile. The Cu(II) centers are axially bridged via long bromine contacts, leading to ferromagnetic exchange (2J = 4.04 cm(-)(1)). Density functional calculations have been carried out, giving a comparable singlet-triplet splitting energy. 1 crystallizes in the triclinic system, space group Ponemacr;, with a = 9.253(3) A, b = 18.159(3) A, c = 7.199(5) A, alpha = 91.31(3) degrees, beta = 107.35(4) degrees, gamma = 104.22(2) degrees, and Z = 2.