A Binuclear Copper(II) Complex with Two Symmetric End-on Azido Bridges. Synthesis, Spectroscopy, Crystal Structure and Magnetism

A binuclear copper(II) complex with two symmetric end-on azido bridges: [Cu₂(tacn)₂(μ-N₃)₂](ClO₄)² · CH₃OH (1), where tacn = 1,4,7-triazacyclononane, has been synthesized and structurally as well as magnetically characterized. Compound (1) has the discrete binuclear structure, bridged by two end-on N₃⁻ anions. The macrocyclic ligand tacn functions as a terminal ligand. The magnetic data of compound (1) were analyzed by means of Ĥ = −2JŜ₁Ŝ₂ − DŜ_z, leading to J = 2.49 cm⁻¹, g = 2.08, D = ±0.97 cm⁻¹, zJ′ = −0.47 cm⁻¹. The ferromagnetic interaction is discussed on the basis of the structural features and is compared with the model structure of Ruiz.     

Novel oxalate-bridged trinuclear FeIII-MII-FeIII (M = Cu and VO) complexes: synthesis and magnetism

Two new heterotrinuclear Fe^III-M^II-Fe^III oxalate-bridged complexes have been prepared, and characterized, namely M^II[(ox)Fe^III(Salen)]₂, [Salen = N,N′-ethylenebis(salicylideneiminate), ox = oxalate, M = Cu (1) and VO (2)]. Based on elemental analysis, conductivity measurements and i.r. spectra, the complexes are proposed to have an oxalate-bridged structure. The magnetic susceptibilities of the complexes were measured over the 4.2–300 K range, giving the exchange integrals J _AB = −4.23 cm⁻¹, J _AA = −2.47 cm⁻¹ for (1) and J _AB = −5.42 cm⁻¹, J _AA = −1.55 cm⁻¹ for (2). These results revealed the operation of an antiferromagnetic spin-exchange interaction between the metal ions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Two new oxamido-bridged trinuclear complexes [Cu<Subscript>2</Subscript>M] (M = Mn(II), Co(II)): synthesis,structures, and magnetic properties

By using the macrocyclic oxamido-copper complex CuL (H₂L = 2,3-dioxo-5,6:13,14-dibenzo-9,10-(O)cyclohexyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) as precursor, two new trinuclear complexes with the formulas [(CuL)₂Mn(ClO₄)₂] (1) and [(CuL)₂Co(ClO₄)₂] (2) have been synthesized and structurally characterized. H-bonds are found between the molecules, which link adjacent trinuclear units together to form a unique one-dimensional structure. The temperature dependence of the magnetic susceptibility for the complexes was analyzed by means of the Hamiltonian leading to J = −14.66 cm⁻¹ and J = −22.9 cm⁻¹ for 1 and 2, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Coordination polymers with adamantanediacetate bridges: syntheses, structures, and magnetic properties

Abstract  Two new coordination polymers, [CoL(bpp)] _n (1) and [MnL(bipy)] _n ·0.25nH₂L·0.5nH₂O (2) (H₂L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. Complex 1 is an one-dimensional (1D) chain structure of Co(II) bridged by L²⁻ as well as bpp. Complex 2 consists of a two-dimensional (2D) (3,6)-connected topology layer structure. Variable temperature magnetic susceptibility measurements in the range of 2–300 K reveal the existence of weak antiferromagnetic interactions in two complexes with J = −1.74 cm⁻¹, g = 2.26 for 1 and J = −0.10 cm⁻¹, g = 1.67 for 2. Index abstract  Two mental-organic frameworks, namely [CoL(bpp)] _n (1) and [MnL(bipy)] _n ·0.25nH₂L·0.5nH₂O (2) (H₂L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), have been synthesized based on 1,3-adamantanediacetic acid and N-donor coligand with metal ions Co(II) and Mn(II). The magnetic measurement of the two polymers reveals typical antiferromagnetism exchange. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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.     

Synthesis,crystal structures,magnetic and luminescent properties of nickel(II) and cadmium(II) coordination polymers bearing 5-(2′-carboxylphenyl) nicotate ligands

Two coordination polymers, namely [M(cpna)(phen)(H₂O)] _n (M = Ni, 1; Cd, 2, H₂cpna = 5-(2′-carboxylphenyl) nicotic acid, phen = 1,10-phenanthroline), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, magnetic and luminescence measurements. Single-crystal X-ray diffraction studies show that the two complexes are isostructural polymers. They have 1D step-like chain structures, which are further extended into 3D metal–organic supramolecular frameworks by π–π stacking interactions. Magnetic studies for complex 1 show antiferromagnetic coupling between the adjacent Ni(II) centers, with g = 2.10 and J = −4.30 cm⁻¹. Complex 2 displays strong green fluorescent emission at room temperature.     

A novel one-dimensional dicyanamide bridged lead(II) complex containing nitronyl nitroxide radicals: Syntheses,crystal structures,and magnetic properties

A novel one-dimensional dicyanamide bridged lead(II) complex containing nitronyl nitroxide radicals, [Pb(NIT-1′-MeBzIm)(Dca)₂] _n (Dca = dicyanamide anion, NIT-1′-MeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. In the complex, Pb²⁺ ion shows seven-coordinate geometry. A chain structure with single, symmetrical, end-to-end Dca bridges is found in the compound. These units develop as 1D species, where dicyanamide ligands bridge Pb²⁺ ions. Otherwise, molecules are linked by π-π-piling interactions to form 2D network structure. Magnetic investigation indicates the existence of intramolecular interactions, wich are ferromagnetic with J = 23.6 cm⁻¹, where the spin Hamitonian is defined as H = −2Σ _i,j J _i,j S _i S within the complex.     

Synthesis,crystal structures,and magnetic properties of two manganese(II) coordination polymers bearing 1,1′-biphenyl-3,3′-dicarboxylate ligands

Two Mn(II) coordination polymers, namely [Mn(bpda)] _n (1) and [Mn(bpda)(bpy)_0.5] _n (2) (H₂bpda = 1,1′-biphenyl-3,3′-dicarboxylic acid and bpy = 4,4′-bipyridine), have been synthesized from H₂bpdc, bpy, and MnSO₄·2H₂O under hydrothermal conditions. The complexes were characterized by physicochemical and spectroscopic methods, as well as by X-ray crystallography. Compound 1 possesses a 3D structure consisting of carboxylate-bridged edge-sharing Mn–O–Mn double chains. Compound 2 features a 3D open structure with a dinuclear Mn(II) secondary building unit. Magnetic susceptibility measurements of compounds 1 and 2 exhibit antiferromagnetic interactions between the nearest Mn(II), with J = –11.3 cm⁻¹ and g = 2.12 for 1, and J = –13.5 cm⁻¹ and g = 2.12 for 2.     

Supramolecular self-assembly of two Cu(II) complexes with 1,2,4-triazole derivatives: syntheses,crystal structures and magnetic properties

Two two-dimensional coordination complexes, {[Cu₄(BTM)₆(OPA)₄] · 4DMF · 3H₂O} _n (1) and {[Cu(BDTM)(OH)](ClO₄) · 2H₂O} _n (2) (BTM = bis(1,2,4-triazol-1-yl)methane, BDTM = bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane, OPA²⁻ = ortho-phthalic dianion, DMF = N,N-dimethylformamide), were synthesized and structurally characterized. Each Cu(II) ion locates in a distorted square pyramidal geometry in 1, in which OPA²⁻ ligands bridge Cu²⁺ ions along a axis to form a magnetic transmission chain and BTM ligands act as flexible spacers to construct the two-dimensional layer structure. In 2, each Cu²⁺ ion adopts tetra-coordination geometry to two hydroxyl groups and two triazolyl nitrogen atoms from two different BDTM ligands. Two hydroxyl groups bridge two Cu²⁺ ions to form a rhombic diamond, and four BDTM ligands connect four diamonds to form a 36-membered macrocyclic structure with large channels along a axis. Magnetic properties revealed that both OPA²⁻ and OH⁻ mediate anti-ferromagnetic interactions between Cu²⁺ ions with J = − 0.06(3) and −301.9(2) cm⁻¹ for 1 and 2, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Copper complexes of 1-[(2-carboxyethyl)benzene]-3-[2-pyridine]triazene

The triazenide, 1-[(2-carboxyethyl)benzene]-3-[2-pyridine]triazene (HL), has been synthesized. In the presence of Et₃N, the reaction of HL with Cu(OAc)₂·H₂O or CuCl₂·2H₂O gives the tetranuclear copper(II) complexes {Cu₄(L)₂(μ₂-OH)₂(OAc)₄} 1 and {Cu₄L₄(μ₄-O)Cl₂} 2, respectively. The X-ray crystal structures of both complexes have been obtained. Magnetic studies indicate significant antiferromagnetic coupling between the copper(II) centers for both complexes, with coupling constants (J) of −493.4 cm⁻¹ for 1 and −165 cm⁻¹ for 2.     

Hydrothermal synthesis,crystal structure and magnetic properties of a new one-dimensional polymer [{Cu(4,4′- bipy)(CH<Subscript>3</Subscript>COO)<Subscript>2</Subscript>}·3H<Subscript>2</Subscript>O]<Subscript>n</Subscript>

One new metal – organic coordination framework formulated as [{Cu(4,4′-bipy)(CH₃COO)₂}·3H₂O]_n (1) (where 4,4′-bipy=4,4′-bipyridine) has been hydrothermally synthesised and characterised by elemental analysis, IR and electronic spectroscopy, variable temperature magnetic moment measurement and single crystal X-ray diffraction study. Single crystal X-ray analysis reveals that 1 is one dimensional polymeric compound in which acetate ligand shows both mono- and bidentate bonding mode, and 4,4′-bipy acts as bridging ligand which supports the formation of infinite chains. The global feature of the χ _M T vs. T curve in 1 is characteristic of moderate antiferromagnetic interaction and the best fit parameters from 300 down to 2 K are found as J = −78.7 cm⁻¹.     

Synthesis,crystal structures and magnetic properties of a radical ligand and its corresponding copper(II) complex

A new chelating radical ligand, IMMeBzIm (IMMeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl) and its copper(II) complex [Cu(IMMeBzIm)₂(ClO₄)]·(ClO₄) have been prepared and characterized by IR, magnetic and single-crystal X-ray analysis. In the crystal structures, both free IMMeBzIm and the complex crystallize in monoclinic space groups P2(1)/c and C2/c, respectively. The structure of IMMeBzIm consists of mononuclear molecules. In the complex, the coordination geometry around copper is a distorted square pyramid, and the apical position is occupied by one oxygen atom of ClO₄ ⁻ anion. A 1-D polymer is formed through intermolecular H-bond interactions. The variable-temperature magnetic susceptibility of the free IMMeBzIm suggests weak antiferromagnetic coupling with J = −1.12 cm⁻¹ where the spin Hamitonian is defined as Ĥ = −2 JŜ ₁ Ŝ ₂ between radical and radical.     

Structure and magnetic properties of a novel heterospin 1-D chain complex containing both Cu(II) and nitroxide radicals as spin branches

A novel heterospin one-dimensional (1-D) chain complex containing both Cu(II) and nitroxide radical ligands, {[Cu(tcph)(H₂O)₄][Cu(tcph)(NIT3Py)₂]·2H₂O} _n (1) (H₂tcph = tetrachloro-phthalic acid, NIT3Py = 2-(3′-pyridyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide), has been synthesized and structurally characterized. The structure consists of neutral chains of copper(II) ions bridged by tcph and coordinated alternatively by nitroxide radicals as spin branches and solvated water as co-ligand. The magnetic data were fitted using an approximate theoretical model based on population analysis to obtain the coupling parameter values of J _Cu2-Rad = 22.4 cm⁻¹ and J′_Cu1-Cu2 = −2.4 cm⁻¹, indicating the intramolecular ferromagnetic interaction between Cu(II) and NIT3Py and weak antiferromagnetic interaction between Cu1 and Cu2 linked by tcph.     

A bimetallic cyano-bridged complex based on nickel(II) and pentacyanidonitrosylferrate(II) precursors: characterization, crystal structure, and magnetic properties

A heterobimetallic cyano-bridged 1D coordination polymer of the composition [Ni(baepn)(μ-NC)Fe(CN)₃(NO)(μ-CN)]_n·3H₂O has been synthesized by the reaction of nickel(II) nitrate hexahydrate, baepn (baepn = N, N′-bis(2-aminoethyl)-1,3-propanediamine), and sodium nitroprusside dihydrate in a methanol–water mixture. The complex was characterized by physicochemical and spectroscopic methods. The crystal structure was established by single-crystal X-ray diffraction analysis. It reveals cyano-bridged heterometallic chains consisting of alternating arrays of Ni(II) and Fe(II) atoms, both being embedded in distorted octahedral environments. Low-temperature susceptibility measurements show the presence of weak antiferromagnetic exchange interactions between paramagnetic Ni(II) centers (J = −0.46 cm⁻¹) through long diamagnetic [Fe(CN)₅(NO)]²⁻ bridges. Spin state of the iron atom was established by ⁵⁷Fe M?ssbauer spectroscopy.     

Synthesis, structure, and properties of a binuclear Fe(III) complex with N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine

Mannich reaction of 2-Amino propanol, 2-tert-butyl-4-methylphenol, and formaldehyde in the ratio of 1:2:2 provides a new compound, N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L), which has been characterized by X-ray crystallography and elemental analysis. In the presence of Et₃N, the reaction of H₃L and FeCl₃·6H₂O gives a dinuclear Fe(III) complex [Fe₂L₂] 1, which has been characterized by X-ray crystallography, magnetic measurement, and cyclic voltammetry. The value of μ_eff at room temperature (5.97 μ_B) is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ZS(S + 1)]^1/2], indicating there are strong coupling interactions between Fe³⁺ ions. The magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = −13.35 cm⁻¹ ). CV of 1 reveals two reversible waves at 0.433 and 1.227 V versus AgCl/Ag, which can be ascribed to the successive redox coupling of Fe^IIFe^II/Fe^IIIFe^II and Fe^IIIFe^II/Fe^IIIFe^III, respectively.     

Effect of ionic conductivity of a PAN–PC–LiClO<Subscript>4</Subscript> solid polymeric electrolyte on the performance of a TiO<Subscript>2</Subscript> photoelectrochemical cell

A nanoparticle TiO₂ solid-state photoelectrochemical cell has been fabricated. The effect of ionic conductivity of a solid electrolyte of polyacrylonitrile (PAN)–propylene carbonate (PC)–lithium perchlorate (LiClO₄) on the performance of a photoelectrochemical cell of indium tin oxide (ITO)/TiO₂/PAN–PC–LiClO₄/graphite has been investigated. A nanoparticle TiO₂ film was deposited onto ITO-covered glass substrate by controlled hydrolysis technique. A solid electrolyte of PAN–LiClO₄ with PC plasticizer prepared by solution casting technique was used as a redox couple medium. The room temperature conductivity of the electrolyte was determined by AC impedance spectroscopy technique. A graphite electrode was prepared onto a glass slide by electron beam evaporation technique. The device shows a photovoltaic effect under illumination. The short-circuit current density, J _sc, and open-circuit voltage, V _oc, vary with the conductivity of the electrolyte. The highest J _sc of 2.82 μA cm⁻² and V _oc of 0.56 V were obtained at the conductivity of 4.2 × 10⁻⁴ Scm⁻¹ and at the intensity of 100 mW cm⁻².     

Two manganese(II) complexes based on anthracene-9-carboxylate: Syntheses,crystal structures,and magnetic properties

Abstract  To explore the influence of the anthracene ring skeleton, with a large conjugated π-system, on the structures and properties of its complexes, two Mn^II complexes with anthracene-9-carboxylate ligand were synthesized and structurally characterized: {[Mn(L)₂(H₂O)₂](H₂O)}_∞ (1) and [Mn₂(L)₄(phen)₂(μ-H₂O)](CH₃OH) (2) (L = anthracene-9-carboxylate and phen = 1,10-phenanthroline). Complex (1) has a one-dimensional (1D) chain structure that is further assembled to form a two-dimensional (2D) sheet, and then an overall three-dimensional (3D) network by π···π stacking and/or C–H···π interactions. Complex (2) makes a dinuclear structure by incorporating the chelating phen ligand, which is further interlinked via inter-molecular π···π stacking and C–H···π interactions to generate a higher-dimensional supramolecular network along the different crystallographic directions. The results reveal that the bulky anthracene ring skeleton in L, by virtue of intra- and/or inter-molecular π···π stacking and C–H···π interactions, plays an important role in the formation of complexes (1) and (2). The magnetic properties of (1) and (2) were further investigated. As expected, the very long inter-metallic separations result in weak magnetic coupling, with the corresponding coupling constant values of J = −10 cm⁻¹ for (1) and J = −2.46 cm⁻¹ for (2). Graphical abstract  The constructions of two new Mn^II complexes comprising 1D chain (1) and dinuclear subunit (2) structures have been successfully achieved by using a bulky anthracene-9-carboxylic acid (HL), together with incorporating the chelating 1,10-phenanthroline as a co-ligand for (2). The result reveals that the bulky anthracene ring skeleton of HL, by virtue of intra- and/or inter-molecular π···π stacking and C–H···π interactions, plays an important role in the formation of the supramolecular architectures of (1) and (2). Moreover, magnetic properties of the complexes have been investigated.      

Synthesis, crystal structures and magnetic properties of cyanide-bridged macrocyclic complexes

Three cyanide-bridged dodecanuclear macrocyclic wheel-like complexes [Cr(bpmb)(CN)₂]₆[Mn(5-Brsalpn)]₆·12H₂O (1), [Co(bpmb)(CN)₂]₆[Mn(5-Brsalpn)]₆·12H₂O (2) and [Co(bpmb)(CN)₂]₆[Mn(5-Clsalpn)]₆·24H₂O·8CH₃CN (3) [bpmb²⁻= 1,2-bis(pyridine-2-carboxamido)-4-methylbenzenate dianion; 5-Brsalpn²⁻ = N,N′-propylenebis(5-bromosalicylideneaminato) dianion; 5-Clsalpn²⁻ = N,N′-propylenebis(5-chlorosalicylideneaminato) dianion] have been synthesized and their crystal structures and magnetic properties have been investigated. The three compounds are structurally isomorphous and consist of alternating Mn(III)-Schiff base cations and [M(bpmb)(CN)₂]⁻ anions, generating cyanide-bridged nanosized dodecanuclear macrocyclic structures with an approximate diameter of 2 nm. The study of the magnetic properties of complex 1 reveals an antiferromagnetic interaction between the Cr(III) and Mn(III) ions through the cyanide bridges. A best-fit to the magnetic susceptibility of the complex leads to a magnetic coupling constant of J _CrMn = −2.65(6) cm⁻¹ on the basis of a one-dimensional alternating chain model with the Hamiltonian $ H = - J_{CrMn} \sum\limits_{i = 0}^N {S_i \cdot S_{i + 1} } $ H = - J_{CrMn} \sum\limits_{i = 0}^N {S_i \cdot S_{i + 1} } .     

Binuclear iron(III) complexes bridged by terephthalato groups

Six new μ-terephthalato iron(III) binuclear complexes have been prepared and identified: [Fe₂(TPHA)(L)₄]-(ClO₄)₄ [L = 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy); 5-methyl-1,10-phenanthroline (Me-phen); 5-chloro-1,10-phenanthroline (Cl-phen) and 5-nitro-1,10-phenanthroline (NO₂-phen)]; where TPHA = the terephthalate dianion. Based on the elemental analyses, molar conductance and magnetic moments of room-temperature measurements, and spectroscopic studies, extended TPHA-bridged structures consisting of two iron(III) ions, each in an octahedral environment, are proposed for these complexes. The [Fe₂(TPHA)(Me-phen)₄](ClO₄)₄ (1) and [Fe₂(TPHA)(phen)₄](ClO₄)₄ (2) complexes were characterized by variable temperature magnetic susceptibility (4–300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, Ĥ = −2JŜ ₁ Ŝ ₂, giving the exchange integrals J = −1.05 cm⁻¹ for (1) and J = −9.28 cm⁻¹ for (2). This result indicates the presence of a weak antiferromagnetic spin-exchange interaction between the metal ions within each molecule. The influence of the terminal ligand methyl substituents on magnetic interactions between the metals is also discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis, crystal structure and magnetic properties of bimetallic complex of Ni2Co(TTHA)·12H2O

The bimetallic complex of Ni₂Co(TTHA)·12H₂O (TTHA = triethylene tetraminehexaacetic acid) was synthesized and characterized structurally and magnetically. The title complex crystallizes in the triclinic space group P ī with a = 0.7316(2), b = 0.8624(2), c = 1.5041(4) nm; α = 73.38(2), β = 83.97(2), γ = 70.50(2)°. The crystal structure is built up of [Ni₂(TTHA)(H₂O)₂]²⁻, Co(H₂O)₆²⁺ and water molecules. The variable magnetic measurement shows that there is strong antiferromagnetic interaction between two Ni(II) ions in [Ni₂(TTHA) (H₂O)₂]²⁻ with J _Ni−Ni = −141.64 cm⁻¹, g _Ni = 2.21 and that the constant of spin-orbit coupling of Co(II) ion is −134.8 cm⁻¹. __________ Translated from Acta Scientiarum Naturalium Universitatis Nankaiensis, 2007, 40(1): 6–10 [译自: 南开大学学报(自然科学版)]