Variable-temperature Magnetic Properties Research Articles

Crystal structure and magnetic properties of a hexacopper(II)-based azide-bridged one-dimensional coordination polymer: A new pattern of azide-bridged network

In the present investigation, synthesis, crystal structure and magnetic properties of an azide-bridged one-dimensional tape-type coordination polymer of copper(II) of composition [CuII6(N,N-diEten)2(μ1,1-N3)8(μ1,1,1-N3)2(μ1,3-N3)2]n (1) are described, where N,N-diEten is N,N-diethylethylenediamine. Compound 1 is formed on reacting Cu(ClO4)2·6H2O, the diamine and NaN3 in 1:0.33:2molar ratio. Compound 1 crystallizes in monoclinic space group and P21/n crystal system. The structure of 1 reveals that it is a hexacopper(II)-based tape-type 1-D polymer having three types of azide ligands, μ1,1-(EO), μ1,3-(EE) and μ1,1,1-; while μ1,1- and μ1,1,1-azide ligands form CuII6 unit, μ1,3-azide ligands interlink the CuII6 units to generate one-dimensional network. Variable-temperature and variable-field magnetic properties of 1 have been studied, revealing overall ferromagnetic interaction. The structure/synthesis procedure/magnetic properties of the title compound are compared with closely similar systems. Interestingly, the pattern of azide-bridged network is new considering metallo-azide compounds of not only copper(II) but also of any other metal ions.

Phenoxo bridged tetranuclear copper(II) and dinuclear zinc(II) complexes of 2,6-diformyl-4-methylphenol-di(benzoylhydrazone): Synthesis, structure, spectra and magnetism

Phenoxo bridged tetranuclear Cu(II) and dinuclear Zn(II) complexes are synhesized namely, Cu4[(L)2(OCH3)2] (1) and Zn2(HL)2 (2) (H3L=[(HOC6H2CH3){2,6-(CHN–NC(OH)(C6H5))(CHN–NC(OH)(C6H5))}]) and characterized by FTIR, UV–Vis, 1H NMR, fluorescence and mass spectrometry. Single crystal X-ray diffraction analysis of 1 shows that the Cu atom possesses a square pyramid environment via bridging of ‘phenolato’-O and ‘enolato’-O of the ligand, additional bridging of ‘methanolato’-O of coordinated CH3OH and monodentate coordination of imine-N. The EPR spectrum of 1 are characterized by g‖=2.286, A‖=169×10−4cm−1, g⊥=2.068, A⊥=17×10−4cm−1 (298K) and g‖=2.283, A‖=178×10−4cm−1, g⊥=2.072, A⊥=15×10−4cm−1 (77K). The study of the variable temperature magnetic properties agrees with a predominant intramolecular antiferromagnetic coupling (2J=−186.5cm−1), rendering a ground state of S=0.

Synthesis, molecular and crystalline architectures, and properties of a mononuclear complex [Co II (benzidine) 2 (NCS) 2 (OH 2 ) 2

One mononuclear cobalt(II) compound of the type [Co(bnzd)2(NCS)2(OH2)2] (1) (bnzd = benzidine) has been isolated through a single-pot reaction of the molecular building components in MeOH–H2O solvent mixture at room temperature and characterized by physico-chemical and spectroscopic methods. The crystal structure of complex 1 has an octahedral geometry with trans, trans, trans orientations in the order (Na,Na), (Nt,Nt), (Ow,Ow) [Na = N(amine), Nt = N(thiocyanate) and Ow = O(water)]. In crystalline state, individual units of 1 are associated by weak cooperative O–H...N, O–H...S and N–H...S hydrogen bonds resulting in a 3D network structure. The compound is redox active and shows luminescence in MeOH solution. Thermal decomposition pattern of 1 reveals the presence of two coordinated water molecules. Variable-temperature magnetic susceptibility measurement shows significant orbital contribution and numerical matrix diagonalization method gives the best fit parameters: α = A*k = 1.43; λ = −130 cm − 1; Δ = − 864 cm − 1; TIP = 0.000975; R = 1.19 × 10 − 4. Mononuclear compound [Co(benzidine)2(NCS)2(OH2)2] (1) was isolated and characterized. Cobalt(II) center adopts an octahedral geometry and individual units of 1 are associated by weak O–H…N/S and N–H…S hydrogen bonds resulting in a 3D network structure. Complex 1 is electroactive and shows luminescence property. Variable-temperature magnetic property shows significant orbital contribution.

C3-symmetric trinuclear copper(ii) species as tectons in crystal engineering

Three new complexes have been obtained using C3-symmetric trinuclear complexes as tectons; [Cu3(felden)(NCS)3(dmf)3] (1), [Cu3(felden)(mand)3]·(C2H5)2O (2), and [Cu3(felden)(dca)3(C2H5OH)]·2H2O (3) (H3felden is the Schiff base resulting from the condensation of 2,4,6-triformylphloroglucinol with N,N-dimethylethylenediamine, mand− is the anion of the R-mandelic acid and dca− is the dicyanamide anion). Compounds 1 and 2 are discrete trinuclear species, while compound 3 is a 2D coordination polymer, constructed from trinuclear nodes and dicyanamido spacers. The variable-temperature magnetic properties of 1–3 have been investigated and they reveal the occurrence of weak antiferromagnetic interactions between the copper(II) ions (−J values ranging from 0.90 to 2.40 cm−1) whose size and trend are dependent on the intramolecular copper–copper separation and nature of the basal chromophore at each copper atom.

Synthesis and coordination chemistry of a potential precursor to a triarylamminium radical cation ditopic ligand

The multi-step synthesis of a new ditopic ligand (7) is reported, which is a potential precursor to a triarylamminium radical cation. The preparation and full characterization of three new bimetallic first row transition metal [M=Mn (8), Ni (9), Cu (10)] coordination complexes containing this ligand are described, including detailed electrochemical and magnetic studies. Of note, a ground triplet state is observed in the bimetallic Cu complex. Chemical oxidation of these precursor complexes generated persistent complexes containing the dication of the ligand, which is confirmed through UV–Vis and EPR spectroscopies. The variable temperature magnetic properties of the dicationic complexes are described and included in the discussion are results from density functional theory calculations of bimetallic radical cation complexes.

CuII Complexes of Isomeric Ligands Derived from 2-Pyridine-carboxaldehyde and m- or p-Xylylenediamine: An Intermolecularly ?-Stacked Dinuclear Species and a Trinuclear Circular Helicate that Encapsulates a Chloride Ion

Di- and trinuclear CuII complexes [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O incorporating the isomeric Schiff base ligands 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L1) and 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L2), each incorporating two separated α-diimine coordination domains, have been synthesised and their X-ray crystal structures and variable temperature magnetic properties determined. The X-ray crystal structure of [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O shows that each CuII centre is bound to two nitrogen atoms from L1, two from a bipyridine ligand, and a chloride anion. Intramolecular π-stacking interactions are present between the central phenyl ring of L1 and both rings of each bipyridine ligand. The structure of [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O shows an unusual trinuclear circular helicate arrangement with approximate C3-symmetry. A chloride anion is encapsulated in the structure being bound by six non-classical hydrogen bond interactions. Variable temperature magnetic susceptibility measurements indicated the presence of weak antiferromagnetic behaviour for [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and weak ferromagnetic behaviour for [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O.

Synthesis, Structural Analysis, and Magnetic Properties of Ethylmalonate-Manganese(II) Complexes

Five manganese(II) complexes of formulas [Mn(2)(Etmal)(2)(H(2)O)(2)(L)](n) (1-4) and {[Mn(Etmal)(2)(H(2)O)][Mn(H(2)O)(4)]}(n) (5) with H(2)Etmal = ethylmalonic acid (1-5) and L = 1,2-bis(4-pyridyl)ethane (bpa) (1), 4,4'-azobispyridine (azpy) (2), 4,4'-bipyridyl (4,4'-bpy) (3), and 1,2-bis(4-pyridyl)ethylene (bpe) (4) were synthesized and structurally characterized by single crystal X-ray diffraction. Their thermal behavior and variable-temperature magnetic properties were also investigated. The structure of the compounds 1-4 consists of corrugated layers of aquamanganese(II) units with intralayer carboxylate-ethylmalonate bridges in the anti-syn (equatorial-equatorial) coordination mode which are linked through bis-monodentate bpa (1), azpy (2), 4,4'-bpy (3), and bpe (4) ligands to build up a three-dimensional (3D) framework. The structure of compound 5 is made up by zigzag chains of manganese(II) ions with a regular alternation of [Mn(H(2)O)(4)](2+) and chiral (either Δ or λ enantiomeric forms) [Mn(Etmal)(2)(H(2)O)](2-) units within each chain. In contrast to the bidentate/bis-monodentate coordination mode of the Etmal ligand in 1-4, it adopts the bidentate/monodentate coordination mode in 5 with the bridging carboxylate-ethylmalonate also exhibiting the anti-syn conformation but connecting one equatorial and an axial position from adjacent metal centers. The manganese-manganese separation through the carboxylate-ethylmalonate bridge in 1-5 vary in the range 5.3167(4)-5.5336(7) Å. These values are much shorter than those across the extended bis-monodentate N-donors in 1-4 with longest/shortest values of 11.682(3) (3)/13.9745(9) Å (4). Compounds 1-5 exhibit an overall antiferromagnetic behavior, where the exchange pathway is provided by the carboxylate-ethylmalonate bridge. Monte Carlo simulations based on the classical spin approach (1-5) were used to successfully reproduce the magnetic data of 1-5.

A novel two dimensional samarium(III) coordination framework with N-(2-Hydroxyethyl)iminodiacetic acid and oxalate ligands: Synthesis, crystal structure and magnetic property

Under hydrothermal conditions, Sm(NO(3))(3)center dot 6H(2)O reacts with N-(2-Hydroxyethyl)iminodiacetic acid (H(3)heidi), oxalic acid (H(2)Ox), in the presence of NiCl(2)center dot 6H(2)O and NaOH, producing a novel two dimensional coordination polymer with the empirical formula of Na[Sm(Hheidi)(Ox)]center dot 2H(2)O (1). X-ray diffraction analyses show that 1 crystallizes in the orthorhombic system, Pna21 space group, a=25.9008(19) angstrom, b=6.2593(5) angstrom, c=8.7624(6) angstrom, in which the network of SmNO(8) and oxalate units forms an extended two dimensional layered structure. To the best of our knowledge, 1 represents the first structurally characterized lanthanide complex containing H(3)heidi ligand. The variable-temperature magnetic property of 1 has been investigated and the results of magnetic determination suggest the existence of a weak antiferromagnetic coupling between the samarium ions. (C) 2011 Elsevier B.V. All rights reserved.

Synthesis and characterization of three-coordinate Ni(III)-imide complexes.

A new family of low-coordinate nickel imides supported by 1,2-bis(di-tert-butylphosphino)ethane was synthesized. Oxidation of nickel(II) complexes led to the formation of both aryl- and alkyl-substituted nickel(III)-imides, and examples of both types have been isolated and fully characterized. The aryl substituent that proved most useful in stabilizing the Ni(III)-imide moiety was the bulky 2,6-dimesitylphenyl. The two Ni(III)-imide compounds showed different variable-temperature magnetic properties but analogous EPR spectra at low temperatures. To account for this discrepancy, a low-spin/high-spin equilibrium was proposed to take place for the alkyl-substituted Ni(III)-imide complex. This proposal was supported by DFT calculations. DFT calculations also indicated that the unpaired electron is mostly localized on the imide nitrogen for the Ni(III) complexes. The results of reactions carried out in the presence of hydrogen donors supported the findings from DFT calculations that the adamantyl substituent was a significantly more reactive hydrogen-atom abstractor. Interestingly, the steric properties of the 2,6-dimesitylphenyl substituent are important not only in protecting the Ni═N core but also in favoring one rotamer of the resulting Ni(III)-imide, by locking the phenyl ring in a perpendicular orientation with respect to the NiPP plane.

π-Extended and Six-Coordinate Iron(II) Complexes: Structures, Magnetic Properties, and the Electrochemical Synthesis of a Conducting Iron(II) Metallopolymer

Herein, we describe the preparation of three new bidentate π-extended derivatives of the ligand N-phenyl-2-pyridinalimine (ppi) containing a 3-thienyl (4) substituent at position 4 of the aniline ring or 2-thienyl (6) or phenyl (2) substituents at each of the 2,5 positions of the aniline rings. Three iron(2+) complexes (7-9) containing these ligands were prepared by combining two equivalents each of 2, 4, or 6 with Fe(NCS)(2), and the resulting neutral, six-coordinate complexes were fully characterized, including with single crystal X-ray diffraction experiments in the case of complexes 7 and 9. Variable temperature magnetic susceptibility and Mössbauer experiments confirm the presence of spin-crossover in complexes 7 and 8, and the unusual solid state variable temperature magnetic properties of complex 9 likely result from crystal packing forces. Electropolymerization of the 2,5-dithienyl-substituted complex (9) produces a conducting and electrochromic metallopolymer film (poly-9).

Pressure-driven thermal spin transition behaviors in mono-nuclear iron(II) compounds: Synthesis, crystal structure and magnetic properties

Abstract Three isostructural mononuclear iron(II) complexes with the similar tripodal ligands had been synthesized and structurally characterized, which exhibit three-dimensional (3D) supramolecular network constructed by S···H―C hydrogen bonding interactions between adjacent iron centers. The variable-temperature magnetic properties of these three complexes under different pressure have been investigated to probe the possibilities of spin transition behavior under external pressure. For 1, the pressure-driven SCO behavior was firstly observed as the application of external pressure, and then the pressure-driven thermal SCO behavior occurs subsequently as the external pressure reached up to a specific value. However, for 2 and 3, no any SCO behaviors could be observed even under high external pressure. Comparison of the crystal structures of the three complexes show that the differences are mostly due to steric effects and weak ligand field originated from the similar tripodal ligands.

Syntheses, crystal structures and magnetic properties of [2 × 1 + 1 × 2] heterotetrametallic and [1 × 1 + 1 × 1] heterodimetallic cocrystals of copper(II) and iron(II/III)

The present work reports syntheses, crystal structures and variable-temperature magnetic properties of three copper(II)–iron(II/III) compounds [{CuIIL1}{FeIIIL1(H2O)2}](ClO4) (1), [{CuIIL1FeII(H2O)3}{CuIIL1}2](ClO4)2 (2) and [{CuIIL2FeII(H2O)3}{CuIIL2}2](ClO4)2·H2O·CH3COCH3 (3), where H2L1=N,N′-ethylenebis(3-ethoxysalicylaldimine) and H2L2=N,N′-o-phenylenebis(3-ethoxysalicylaldimine). Compounds 2 and 3 are tetrametallic [2×1+1×2] cocrystals of one diphenoxo-bridged dinuclear CuIIFeII and two mononuclear CuII moieties, while compound 1 is a dimetallic [1×1+1×1] cocrystal of one mononuclear FeIII and one mononuclear CuII moieties. The overall topology of 1 is one-dimensional. Tetrametallic (in 2 and 3) and one-dimensional (in 1) self-assemblies are generated due to weak noncovalent interactions. Variable-temperature magnetic susceptibility measurements reveal that iron(II) or iron(III) centers in 1–3 remain in high-spin state. Compounds 2 and 3 exhibit weak antiferromagnetic interaction; the J values in the dinuclear core are −22.5 and −13.7cm−1, respectively, compound 1 exhibits very weak antiferromagnetic interaction (J=−0.25cm−1) propagated through the weak noncovalent bonds.

A Series of 2D and 3D Novel Lanthanide Complexes Constructed from Squarate C4O42–: Syntheses, Structures, Magnetic Properties, and Near-infrared Emission Properties

The solvothermal combination of trivalent lanthanide metal precursors with a squarate ligand (H2C4O4, 3,4-dihydroxy-3-cyclobutene-1,2-dione) has afforded the preparation of a family of eight new coordination polymers, [Ln2(C4O4)3(H2O)4] (Ln = La–Nd, Ho) (1–5), [Ln2(C4O4)3(H2O)8] (Ln = Er, Dy) (6, 7), and Tb2(C4O4)2(C2O4)(H2O)4 (8). Structural analysis reveals that the squarate ligand displays versatile coordination modes to generate novel 2D and 3D frameworks. Three new coordination modes, a bidentate/monodentate μ3 and two bidentate/monodentate μ4 coordination modes, are first reported. In addition, the variable-temperature magnetic properties of the Pr, Nd, Ho, Dy, and Tb complexes, the solid-state near-infrared luminescence spectra of the Pr, Nd, Ho, and Er complexes, and their thermogravimetric analyses are discussed.

A new three-dimensional cobalt(II) coordination polymer based on biphenyl-2,2′,6,6′-tetracarboxylic acid and 1,2,4-triazole: Synthesis, crystal structure and magnetic properties

Abstract A new three-dimensional coordination polymer with the formula [Co(bta)0.5(Htz)(H2O)]n ( 1 ) (H4bta = biphenyl-2,2′,6,6′-tetracarboxylic acid and Htz = 1,2,4-triazole), has been hydrothermally synthesized and structurally characterized. The structure of 1 can be considered as two-dimensional [Co(bta)(H2O)]n layers, consisting of one-dimensional [Co(COO)]n chains, which are separated by bta ligands, and neutral Htz pillars. The variable temperature magnetic property study indicates that there is a weak antiferromagnetic coupling interaction between Co(II) ions, which mainly arises from the antiferromagnetic coupling interaction in the one-dimensional [Co(COO)]n chains through syn–anti carboxylate bridges.

Iron(II) complexes containing thiophene-substituted “bispicen” ligands — Spin-crossover, ligand rearrangements, and ferromagnetic interactions

The synthesis and characterization of three new tetradentate “bispicen-type” ligands containing a substituted thiophene heterocycle are described [2,5-thienyl substituents = H (7), Ph (8), or 2-thienyl (9)]. Iron(II) bis(thiocyanate) coordination complexes containing 7–9 were prepared, and the electronic and variable-temperature magnetic properties of complexes containing 7 (10) and 9 (12) are described. Complex 10 features a gradual and incomplete spin crossover in the solid state, and 12 remains high-spin over the entire temperature range. Complex 11 is extremely unstable and rearranges to another iron(II) complex (13), which was structurally characterized. The temperature-dependent magnetic properties of 13 are described as a one-dimensional ferromagnetic chain, with interchain antiferromagnetic interactions and (or) zero-field splitting dominant at low temperatures. The magnetic analysis is corroborated by the molecular packing and density functional theory calculations, which suggest intermolecular interactions between coordinated thiocyanate ligands bearing a significant spin density.

Syntheses, crystal structures, and magnetic and luminescent properties of a series of lanthanide coordination polymers with chelidamic acid ligand

A series of lanthanide(III) complexes with chelidamic acid ligand, [Ln(C 7H 2NO 5)·3H 2O] n · nH 2O (Ln = La ( 1), Y ( 2), Sm ( 3), and Nd ( 4)), [Gd 2(C 7H 2NO 5) 3·4H 2O] n ·2 nH 2O ( 5) and [Ce(C 7H 2NO 5)·1.5H 2O] n ( 6), have been synthesized by hydrothermal method and structurally characterized by single-crystal X-ray diffraction. Complexes 1– 4 are isostructural and possess 2D framework. Complex 5 contains two different Gd(III) ions linked through carboxylate group to form a 2D framework. Complex 6 exhibits a (4 4) topology 2D network. The variable-temperature magnetic properties of 3 and 5 have been investigated. Furthermore, the photoluminescent properties of 1, 2, 3, and 5 at room temperature were also studied.

Formation of out of plane oxime metallacycles in [Cu 2] and [Cu 4] complexes

The reaction of Cu(ClO 4) 2·6H 2O with dimethylglyoxime (H 2dmg) in a 1:1 mole ratio in aqueous methanol at room temperature affords the dinuclear complex [Cu 2( μ-Hdmg) 4] ( 1). Reaction of 1 with [Cu(bpy)(H 2O) 2](ClO 4) 2 (bpy = 2,2′-bipyridine) in a 1:1 mole ratio in aqueous methanol at room temperature yields the tetranuclear complex [Cu 4( μ-Hdmg) 2( μ-dmg) 2(bpy) 2(H 2O) 2](ClO 4) 2 ( 2). The direct reaction of Cu(ClO 4) 2·6H 2O with H 2dmg and bpy in a 2:2:1 mole ratio in aqueous methanol at room temperature also yields 2 quantitatively. The complexes 1 and 2 were structurally characterized by X-ray crystallography. Unlike the binding in Ni/Co-dmg, two different types of N−O bridging modes during the oxime based metallacycle formation and stacking of square planar units have been identified in these complexes. The neutral dinuclear complex 1 has CuN 4O coordination spheres and complex 2 consists of a dicationic [Cu 4( μ-Hdmg) 2( μ-dmg) 2(bpy) 2(H 2O) 2] 2+ unit and two uncoordinated ClO 4 − anions having CuN 4O and CuN 2O 3 coordination spheres. The two copper(II) ions are at a distance of 3.846(8) Å in 1 for the trans out of plane link and at 3.419(10) and 3.684(10) Å in 2 for the trans out of plane and cis in plane arrangements, respectively. The average Cu–N oxime distances are 1.953 and 1.935 Å, respectively. The average basal and apical Cu−O oxime distances are 1.945, 2.295 and 2.429 Å. The UV–Vis spectra of 2 is similar to the spectrum of the reaction mixture of 1 and [Cu(bpy)(H 2O) 2] 2+. Variable temperature magnetic properties measurement shows that the interaction between the paramagnetic copper centers in complex 1 is antiferromagnetic in nature. The EPR spectra of frozen solution of the complexes at 77 K consist of axially symmetric fine-structure transitions (Δ M S = 1) and half-field signals (Δ M S = 2) at ca. 1600 G, suggesting the presence of appreciable Cu–Cu interactions.

A mononuclear complex and a cubane cluster from the initial use of 2-(hydroxymethyl)pyridine in nickel(II) carboxylate chemistry

The reactions of 2-(hydromethyl)pyridine, hmpH, with Ni(O 2CMe) 2·4H 2O in H 2O, in the absence of counterions, have been investigated. The synthetic study has led to the two new complexes [Ni(O 2CMe) 2(hmpH) 2] ( 1) and [Ni 4(O 2CMe) 4(hmp) 4(H 2O) 2] ( 2). Complex 1 can also be transformed into 2 by reacting with an excess of NaOH in H 2O. The structures of 1 and 2·2.25H 2O·0.5(1,4-dioxane) have been solved by single-crystal, X-ray crystallography. The octahedral Ni II center in centrosymmetric 1 is coordinated by two 1.10 (Harris notation) MeCO 2 − groups and two N, O-chelating (1.11) hpmH ligands. The tetranuclear cluster molecule of 2·2.25H 2O·0.5(1,4-dioxane) possesses a distorted cubane {Ni 4(μ 3-OR′) 4} 4+ core [R′ = (2-pyridyl)CH 2–] with the Ni II ions and the oxygen atoms from the 3.31 hmp − ligands occupying alternate vertices of the cube. Two 2.11 MeCO 2 − groups cap two opposite faces of the cube, while two 1.10 MeCO 2 − ions and two aqua ligands complete the octahedral coordination sphere of the metal centers. Characteristic IR bands for the two complexes are discussed in terms of the nature of bonding and the structures of the two complexes. The variable-temperature magnetic properties of 2 have been modeled with two J values, and reveal antiferromagnetic exchange interactions between the four Ni II ions to give a diamagnetic ground state.

Synthesis, crystal structures, magnetic and luminescent properties of unique 1D p-ferrocenylbenzoate-bridged lanthanide complexes

Treatments of p-ferrocenylbenzoate [ p-NaOOCH 4C 6Fc, Fc=( η 5-C 5H 5)Fe( η 5-C 5H 4)] with Ln(NO 3) 3· nH 2O afford seven p-ferrocenylbenzoate lanthanide complexes {[ Ln(OOCH 4C 6Fc) 2( μ 2-OOCH 4C 6Fc) 2(H 2O) 2](H 3O)} n [ Ln=Ce ( 1), Pr ( 2), Sm ( 3), Eu ( 4), Gd ( 5), Tb ( 6) and Dy ( 7)]. X-ray crystallographic analysis reveals that the isomorphous complexes {[Ce(OOCH 4C 6Fc) 2( μ 2-OOCH 4C 6Fc) 2(H 2O) 2](H 3O)} n ( 1) and {[Pr(OOCH 4C 6Fc) 2( μ 2-OOCH 4C 6Fc) 2(H 2O) 2](H 3O)} n ( 2) form a unique 1D double-bridged infinite chain structure bridged by μ 2-OOCH 4C 6Fc groups. Each Ln(III) ion adopts a dodecahedron coordination environment with eight coordinated oxygen atoms from two terminal monodentate coordinated FcC 6H 4COO − units, two terminal monodentate coordinated H 2O molecules and four μ 2- −OOCH 4C 6Fc units. The luminescent spectra reveal that only 4 and 6 exhibit characteristic emissions of lanthanide ions, Eu(III) and Tb(III) ions, respectively. The variable-temperature magnetic properties of 5 and 7 suggest that a ferromagnetic coupling between spin carriers may exist in 5.

Self-assembly of mixed-valence Co(ii/iii) and Ni(ii) clusters: azide-bridged 1D single chain coordination polymers comprised of tetranuclear units, tetranuclear Co(ii/iii) complexes, ferromagnetically coupled azide-bridged tetranuclear, and hexanuclear Ni(ii) complexes: synthesis, structural, and magnetic properties

One-pot reactions between 2,6-diformyl-4-methylphenol (DFMP) and 2-aminoethanol (AE) in the presence of cobalt(II) salts [Co(ClO4)2, CoCl2, Co(CH3CO2)2, Co(NO3)2] and sodium azide result in the self-assembly of novel one-dimensional single chain mixed-valence cobalt coordination polymers {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]ClO(4).5H2O.CH3OH}n (1), {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]Cl.H2O}n (2) in which tetra-cobalt cationic units are bridged by symmetrical 1,3-azides, forming single chains; mixed valence neutral tetranuclear clusters [Co2(II)Co2(III) (HL)2(OCH3)2(N3)4]CH3OH.2H2O (3), [Co2(II)Co2(III)(HL)2(OCH3)2(N3)2(CH3CO2)2].2CH3OH.2H2O (4), and the cationic cluster [Co2(II) Co2(III) (HL)2(OCH3)2(CH3OH)2(N3)2](NO3)2 (5). In all these reactions, H3L, the potentially pentadentate (N2O3), trianionic double Schiff base ligand 2,6-bis[(2-hydroxy-ethylimino)-methyl]-4-methylphenol is formed. The reaction between DFMP and AE in the presence of nickel(ii) salts and sodium azide in methanol-water mixture results in the self-assembly of ferromagnetically coupled hexanuclear complexes [Ni6(H2L)2(HL-1)2(H2O)2(N3)6](ClO4)(2).2CH3OH (6), and [Ni6(H2L)2(HL-1)2(CH3OH)2(N3)6](BF4)2 (7), involving double (H3L) and single (H2L-1) Schiff base ligands, and a neutral tetranuclear complex [Ni4(H2L)2(OCH3)2(CH3CO2)2(N3)2] (8) with only double Schiff-base (H3L). In these complexes, the nature of the anion and the reaction conditions seem to play an important role in directing the formation of tetranuclear, hexanuclear or polymeric clusters. All complexes involve divacant double cubane-type cores containing three to four different types of bridging ligands (phenoxy, azido, methoxy/alkoxy, and acetate). Variable temperature magnetic properties of these spin coupled clusters have been investigated and magneto-structural correlations have been established.