Synthesis,spectral, magnetic and electrochemical properties of new dimeric copper(II) complexes

Four new ligands, bis-[3,5-disubstituted-2-hydroxybenzyl]-N-alkylamines (L¹–L⁴) with three potential donor sites, capable of forming dimeric copper(II) complexes have been prepared. The dimeric nature of the complexes has been confirmed by FAB mass spectral studies. Molar conductance studies indicate that the complexes are neutral. Electrochemical studies indicate that the complexes undergo quasi reversible two step single electron transfers at negative potentials (E_pc¹=−0.34 to −0.48 V, E_pc²=−0.59 to −0.72 V). Variable temperature magnetic studies indicate that the complexes are antiferromagnetically coupled (−2J=290 to 400 cm⁻¹). ESR spectral studies in DMF indicate that the complexes are dimeric and undergo dissociation on addition of pyridine.     

Structure and magnetic properties of Cu(II) bischelate with spin-labeled aminoenal

The molecular and crystal structure of Cu(II) bischelate with the deprotonated stable nitroxide radical 4,4,5,5-tetramethyl-2-(2-oxo-1-(4,4,5,5-tetramethylimidazolidine-2-ylidene)ethyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxylom (HL) are studied. It is revealed that the complex packing is formed of separate CuL₂ molecules. Oxygen atoms in >N∸O groups do not participate in Cu²⁺ ion coordination, and so only weak exchange interactions are observed between paramagnetic centers in CuL₂.     

Structure and magnetic properties of a mixed‐ligand copper(II) complex

The hydrothermal synthesis of the novel complex poly[[μ₂‐N¹,N⁴‐bis(pyridin‐3‐yl)naphthalene‐1,4‐dicarboxamide‐κ²N³:N^3′](μ₄‐phthalato‐κ⁴O¹:O¹:O^1′:O^2′)copper(II)], [Cu(C₈H₄O₄)(C₂₂H₁₆N₄O₂)]_n, is described. With the phthalate ligand connecting neighbouring Cu^II cations, an infinite one‐dimensional chain is formed. Adjacent one‐dimensional chains are connected by the dicarboxamide ligand, forming an intriguing two‐dimensional framework. The magnetic properties and thermal stability of this complex are also described.     

钴(Ⅱ)和铜(Ⅱ)膦酸配位聚合物的热、磁性能

3-氨基-1-羟基丙叉-1,1-二膦酸与钴或铜离子的水热反应得到新的配聚物Co2(NH3CH2CH2C(OH)(PO3)(PO3H))2·2H2O (1) 和Cu3{[NH3CH2CH2C(OH)(PO3)2](H2O)2} (2).研究了两个配合物的热稳定性,采用变温磁化率研究了在5-300 K范围内的磁性能. 结果表明:在配合物1中,钴离子间存在着弱的反铁磁偶合作用,理论拟合值为J=-2.1 cm-1,g=2.18;配合物2中,铜离子间的磁作用较复杂.     

Structure and magnetic properties of carbonate-bridged five-coordinate nickel(II) complexes controlled by solvent effect

CO2 and HCO3- react with the dinuclear hydroxo-complex [Ni(mcN3)(mu-OH)]2(PF6)2 (mcN3 = 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene) to form micro-CO3 bridged nickel(II) complexes, [{Ni(mcN3)}2(mu-CO3)](PF6)2 (1a) with a symmetric core in which both nickel atoms are five-coordinate and [Ni(mcN3)(mu-CO3)Ni(mcN3)(MeCN)](PF6)2 (1b) with an asymmetric dinuclear core containing five- and six-coordinate nickel atoms. The magnetic behaviour indicates the existence of antiferromagnetic coupling between the metallic centres. A substantial increase in the value of J occurs when the symmetric five-coordinate nickel species transforms to an asymmetric five- and six-coordinate species by axial coordination of acetonitrile.     

Structure and magnetic properties of layered high-spin Co(II)(l-threonine)2(H2O)2

We report the structure and the magnetic properties of a cobalt(II) compound with the amino acid l-threonine, Co(C(4)H(8)NO(3))(2)(H(2)O)(2). It crystallizes in the orthorhombic chiral space group C222(1), with a = 5.843(5) A, b = 10.120(10) A, c = 22.36(3) A, and Z = 4. The Co(II) ion is in a deformed octahedral environment on a 2-fold symmetry axis parallel to the crystallographic axis b. It is bonded to two threonine molecules in a bidentate fashion, via one oxygen from the carboxylate end and the alpha-amino nitrogen. A water molecule occupies the third independent site. The Co(II) ions are arranged in layers with intralayer and interlayer distances of 5.84 and 11.18 A, respectively. Magnetic measurements data reflect the molecular character of a compound with weak exchange interactions. EPR measurements in polycrystalline and single-crystal samples indicate a distorted axial symmetry around the Co(II) ion, as expected from the structural results. Eigenvalues and eigenvectors of the g tensor are determined. The measured principal g values (5.81, 4.56, and 2.23) reflect a high-spin Co(II) ion, as suggested by the type of ligands and the molecular symmetry. From the incomplete collapse of the hyperfine structure we estimate 0.25 < |J| < 1.2 cm(-1) between neighboring Co(II) ions within a layer, transmitted through H-bonds. A higher limit |J'| < 0.07 cm(-1) is estimated for the exchange interactions between Co(II) ions in neighboring layers. From a global fit of a spin Hamiltonian with spin (3)/(2) to magnetization and EPR data we obtain a zero field splitting delta approximately 231 cm(-1) between the two lowest doublet states. The results are discussed in terms of the molecular and electronic structure of the compound.     

Structure and magnetic properties of the copper(II) complexes with diacyl hydrazides of salicylic acid

The structures and results of the static magnetic susceptibility investigation of the copper(II) binuclear complex with salicylic acid diacyl hydrazide (H₂L), [Cu₂(L)(Py)₄] (I), and the copper(II) trinuclear complex with diacyl dihydrazide of salicylic and glutaric acids (H₆L′), [Cu₃(L′)(Py)₄] · 2Py (II), are described. The exchange antiferromagnetic interactions between the paramagnetic centers with the exchange interaction parameter −2J = 119 cm⁻¹ for dimer I and 14 cm⁻¹ for trinuclear complex II are detected.     

Structure and magnetic properties of a new dinuclear nickel(II) complex with a dinucleating hexaazamacrocycle

The crystal structure and magnetic properties of a new dinuclear nickel(II) complex [LNi2(AcO)4]·14H2O, where L = 3,6,9,17,20,23-hexaazatricyclo [23.3.1.111,13] triaconta-1(29),11(30),12,14,25(26),27-hexene, has been studied. X-ray structure analysis shows that the compound consists of a discrete [LNi2(AcO)4] complex and 14 lattice water molecules. Each Ni atom is six coordinated by three N atoms from the macrocycle and three O atoms from the two coordinated acetates; two nickel atoms in each macrocycle are at the distance of 7.028Å. The result of the magnetic measurement indicates that the zero-field splitting constant of nickel(II) centres |D| = 1.87 cm–1.     

Structure and magnetic properties of a new cobalt(II) thiophenedicarboxylate coordination polymer showing unprecedented coordination

A new carboxylato-bridged CoII network of formula {Co((kappa1-kappa1)-(kappa1-mu2)-mu4-TDC)(mu2-H2O)0.5(H2O)}n (H2TDC=2,5-thiophenedicarboxylic acid) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and IR and UV-visible spectroscopies. The title compound is made of chains of CoII dimers interconnected by TDC2- ligands, showing an unprecedented asymmetric tetradentate coordination mode of the carboxylate functions. Magnetic measurements show weak ferromagnetic interactions between the Co ions within the dimers.     

Structure and photophysical properties of a dimeric Zn(II) complex based on 8-hydroxyquinoline group containing 2,6-dichlorobenzene unit

A novel 2-substituted-8-hydroxyquinoline ligand (E)-2-[2-(2,6-dichlorophenyl)ethenyl]-8-hydroxyquinoline (HL) was synthesized and characterized by ESI-MS, NMR spectroscopy, and elemental analysis. Using solvothermal method, a dimeric complex (ZnL₂)₂ (1) was fabricated by self-assembly of Zn(II) ions with ligand HL. X-ray structural analysis shows that 1 exhibits a binuclear core, which is bridged by two 8-hydroxyquinoline rings. The supramolecular structure of 1 features a lamellar solid constructed by aromatic stacking interactions, Cl?Cl interactions and nonclassical C–H?Cl hydrogen bonds derived from 2,6-dichlorophenyl group of the ligand HL. The aggregation behavior of zinc salts and HL in solutions was investigated with a variety of techniques, including ¹H NMR, UV–vis, and photoluminescence (PL). In addition, we also studied the photophysical properties of compound 1 by UV–vis and PL. The experimental results show that the complex 1 emits yellow luminescence in the solid state.     

Structure and spectral properties of phenyldiazonium tetrachlorocuprate (II)

Optimized equilibrium structure of phenyldiazonium tetrachlorocuprate(II) and its vibrational spectra were studied by performing quantum-chemical calculations by the B3LYP/6-31G(d,p) density functional method. A comparison with the isolated phenyldiazonium cation was made. An orbital structure of phenyldiazonium tetrachlorocuprate(II) is suggested to account for the activity of compounds of this kind as effective arylating reagents for olefins under the Meerwein reaction conditions.     

Synthesis and magnetic properties of dithiooxamide-bridged nickel(II) complexes

Two novel nickel(II) dinuclear complexes [Ni2(cyclam)2- (DTA)](ClO4)2 (1) and [Ni2(TAA)2(DTA)] (ClO4)2 (2) (TAA=N(CH2CH2NH2)3 , cyclam = 1,4,8,11-tetraazacyclotetradecane, DTA=dithiooxamide) have been prepared and studied by elemental analyses, i.r. and electronic spectra and magnetic measurements. The magnetic susceptibility temperature dependence was measured over the 77–300K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator (H=–2JS1S2) giving the exchange integral J=–23.09cm–1 for (1) and J= –26.0cm–1 for (2).     

Structure and magnetic properties of binuclear copper(II) complexes with 2,6-diformyl-4-tert-butylphenol bis(imidazolinyl)hydrazone

Binuclear copper(II) complexes with bis(imidazolinyl)hydrazone of 2,6-diformyl-4-tert-butylphenol have been prepared and studied. In all complexes the antiferromagnetic exchange interaction between the copper(II) ions is observed.     

Spectral and magnetic properties of copper(II) furoate and copper(II) thiophene-2-carboxylate

Anhydrous copper(II) furoate and copper(II) thiophene-2-carboxylate have been Synthesized. They are formulated as dimeric species with four carboxylate bridges. The thiophene and furan moieties give rise to polymeric structures. Electron spin resonance spectra and magnetic susceptibility measurements show that the dimers have a singlet ground state and a thermally populated triplet state. The exchange coupling constants, 2J, are ?322 and ?312 cm^?1 for the furoate and thiophene-2-carboxylate complexes, respectively. The electronic and infrared spectra are also discussed.     

Supramolecular architecture and magnetic properties of copper(II) and nickel(II) porphyrinogen-TCNQ electron-transfer salts

The compounds [Cu(Tz)-(MeOH)2](TCNQ)2 (1), [Ni(Tz)-(MeOH)2](TCNQ)2 (2), [Cu(Tz)2]-(TCNQ)7 (3) and [Ni(Tz)2](TCNQ)7 (4) (Tz = 2,7,12,17-tetramethyl-1,6,11,16-tetraazaporphyrinogen) were obtained by metathesis reaction of [M(Tz)](ClO4)2 with LiTCNQ and Et3NH(TCNQ)2, respectively. They were characterized by a combination of spectroscopic and physical methods. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 8.310(2), b = 25.180(4), c = 20.727(4) A, beta = 93.58(2) degrees; Z = 4. Compound 3 crystallizes in the triclinic space group P1 with a = 11.244(1), b = 16.700(1), c = 17.321(1) A, a = 113.47(1), beta = 108.52(1), gamma = 96.12(1) degrees; Z = 2. The asymmetric unit of the compound 1 is formed by cationic [Cu(Tz)(MeOH)2]2+ and by two crystallographically non equivalent TCNQ.- anions; these anions form dimeric units by overlap of the pi clouds. The dimers form hydrogen bonds with the metal-lomacrocyclic cation through the methanol ligands. According to this structure the compound is paramagnetic and behaves as an insulator in the temperature range studied. The paramagnetism arises only from the metal-complex moieties. Compound 3 shows an unprecedented structure due to the steric requirements of the macrocycle that favors the stacking of the TCNQ groups. The structure consists of infinite stacks of TCNQ units separated by the metal-macrocyclic units; there are seven TCNQ molecules per formula unit, one of which is formally mono-anionic, while the other six bear one half of an electron per molecule. The copper is six-coordinate in a very distorted octahedral environment. The Tz ligand is located in the equatorial plane and the apical nitrogens of the nitrile groups of two TCNQ molecules complete the coordination around the copper. The compound is a semiconductor and its magnetic behavior can be explained by the sum of the Curie contribution of the metal complex and the contribution arising from the magnetic-exchange interactions of the spins located on the TCNQ units. The latter is found to be typical of one-dimensional antiferromagnetic distorted chains of S = 1/2 spins and can be fitted according to a one-dimensional Heisenberg antiferromagnetic model.     

Crystal structures and magnetic properties of nitroxide radical-coordinated copper(II) and cobalt(II) complexes

Transition Metal Chemistry - The crystal structures and magnetic properties of three coordination compounds constructed from various nitroxide radicals L and MII(hfac)2(H2O)2 building blocks...