Chloro and azido bonded manganese complexes: synthesis,structural, and magnetic studies

Two manganese complexes, [Mn₂(tptz)₂Cl₄] · CH₃CN (1) and [Mn(tptz(ac)(N₃)(H₂O)] · H₂O (2) (where tptz = 2,4,6-tri(2-pyridyl)-1,3,5-triazine, ac = acetate anion), were synthesized and characterized by elemental analyses, infrared spectra, and UV–Vis absorption spectral analyses. The structures of both the complexes were determined by single crystal X-ray diffraction analysis. Complex 1 is binuclear with chloro-bridged manganese ions at the Mn–Mn separation of 3.777(27) Å. Each manganese center in 1 is six coordinate with three nitrogens from a tridentate tptz, three chlorides (one terminal and two bridging), adopting a centrosymmetric distorted octahedral geometry. Various hydrogen bonds form 2-D spiral structures in 1 with Mn–Mn separation of 7.421(2) Å along a-axis and 9.121(2) Å along b-axis. Complex 2 is seven coordinate with pentagonal bipyramidal geometry. The metal center coordinates to three nitrogens from tptz, two oxygens from acetate, one nitrogen from azide, and one oxygen from water. It has a 1-D layered structure, where three independent molecules are linked by uncoordinated water present in the lattice. Magnetic susceptibility in the temperature range 5–300 K for 1 shows the presence of antiferromagnetic interaction between the local high-spin manganese(II) ions with J = ?0.17 cm^?1.     

Unique manganese phosphorus complex with a Mn5P7 core: synthesis, molecular structure, and magnetic properties

The manganese phosphorus cluster [Mn5{N(SiMe3)2}{mu4-PSiiPr3}2{mu-P(H)SiiPr3}5] containing an unusual Mn5P7 core structure and three short Mn-Mn distances was obtained from the reaction of Mn{N(SiMe3)2}2 with H2PSiiPr3. Quantum chemical investigations indicated the presence of comparably strong intramolecular antiferromagnetic interactions leading to a total S = 5/2 spin ground state, which was confirmed by magnetic measurements.     

From low-dimensional manganese(II) azido motifs to higher-dimensional materials: structure and magnetic properties

Four new inorganic-organic hybrid coordination polymers in which 1D or 2D manganese(II) azido inorganic motifs are interlinked into higher-dimensional networks have been synthesized by use of a series of bis(pyridyl)-type organic bridging ligands (linkers) with different side groups and/or different coordination orientations. The dimensionality and the topology of the manganese(II) azido motif and the whole structure are sensitive to the organic linkers used. Compounds 1 and 3 are 3D coordination polymers with pillared-layer architectures: in 1, 2D Mn(II) layers with alternate double end-on (EO) and single end-to-end (EE) azido bridges are pillared by zigzag organic linkers, and 3 is built from single EE azido-bridged Mn(II) layers and linear organic linkers. The 3D nets of 1, 3, and related compounds have been related to the specific length and coordination orientation of the organic pillars and the undulate shape of the manganese(II) azido layers. Consistent with their structures, both 1 and 3 exhibit weak ferromagnetism due to spin canting. Compound 1 is a weak ferromagnet with T(c) = 16 K, and 3 is a metamagnet with T(c) = 23 K. On the other hand, compounds 2 and 4 are 2D coordination networks in which 1D manganese(II) azido chains are interlinked by organic linkers: 2 is the first 2D network built from Mn(II) chains with alternate double EE and double EO azido bridges, which mediate antiferro- and ferromagnetic interactions, respectively; 4 is the first 2D network built from Mn(II) chains with only single EE azido bridges, which mediate antiferromagnetic interactions. The magnetic susceptibility of 4 exhibits a rapid rise at very low temperature, which may be attributed to paramagnetic impurities or spin canting.     

Synthesis,structure, and magnetic properties of a hexanuclear manganese complex

The reaction of 1-(2-pyridyl)-3-(p-tolyl)propane-1,3-dione (HL) with [Mn₃O(O₂CPh)₆(H₂O)(py)₂] in CH₂Cl₂ affords a mixed-valence ${\mathrm{Mn}}_3^{\text{II}}{\mathrm{Mn}}_3^{\text{III}}$ hexanuclear complex [Mn₆O₂(O₂CPh)₈L₃] (1). Complex 1 contains a $[{\mathrm{Mn}}_3^{\text{II}}{\mathrm{Mn}}_3^{\text{III}}({\mathrm{\mu }}_4\text{-}\mathrm{O}{)}_2{]}^{11+}$ core, which is a new structural type in the family of Mn₆ complexes. Variable temperature magnetic susceptibility and magnetization measurement of complex 1 have been carried out. The magnetic data indicate that complex 1 has a ground state spin value of S = 7/2 with significant magnetoanisotropy as gauged by the D value of −0.46 cm⁻¹. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for complex 1 indicates the slow magnetic relaxation of a superparamagnetic molecule.     

A novel nitronyl nitroxide radical containing thiophene and pyridine rings and its manganese(II) complex: synthesis,structure, and magnetic properties

A novel nitronyl nitroxide NIT-thien-3-Py (2-(3-(m-pyridyl)-2-thienyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and its Mn(II) complex [Mn(hfac)₂(NIT-thien-3-Py)]₂ (hfac = hexafluoroacetylacetonate) have been obtained. X-ray analysis indicates that the Mn(II) complex possesses a cyclic dimer structure in which two radical ligands link two Mn(II) ions through their NO groups and pyridine rings. The study of the magnetic data indicates that the manganese(II) ion strongly and antiferromagnetically interacts with the directly bonding NO group and there is weak ferromagnetic coupling between two Mn–NO pairs through the thiophene and pyridine rings of the radical ligand in agreement with a spin polarization mechanism.     

Di-radical dinuclear copper complex: synthesis,structure, and magnetic properties

The reaction of Cu(Ac)₂·4H₂O with 2-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-2hydroxymethyl-propane-1,3-diol (H₄L) and 4,4′-bipyridyl-N,N′-dioxide (4,4′-bipy-NO) in DMF under solvothermal conditions leads to the formation of a di-radical dinuclear copper complex [Cu₂(4,4′-bipy-NO)(dcdmap)₄] (1) (dcdmap is the anion of 2,4-dichloro-6dimethylaminomethyl-phenol, synthesized by an in situ reaction). Compound 1 was characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complex 1 displays dominant anti-ferromagnetic interaction between oxyradicals and copper ion and oxyradical.     

An azido-metal-isonicotinate complex showing long-range ordered ferromagnetic interaction: synthesis, structure and magnetic properties

A new 3D Cu(II) complex [Cu1.5(N3)2(isonicotinate)]n [1], which features two types of bridging modes for azide (mu(1,1) and the rare asymmetric mu(1,1,3)) where the three bonds of the mu(1,1,3)-N3(-) group to Cu exhibit three different distances, has been synthesized and characterized, and magnetic measurements indicate that [1] experiences long-range ferromagnetic ordering at approximately 6 K.     

New divalent manganese complex with pyridine carboxylate N-oxide ligand: Synthesis, structure and magnetic properties

Two new manganese complexes, [Mn₃(L¹)₄(NO₃)₂]_n (1, HL¹=nicotinate N-oxide acid) and [MnL²Cl]_n (2, HL²=isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L¹ ligands take two different coordinated modes bridging four and three Mn^II ions. The nitrate anions take chelating coordination modes, leading one type of the Mn^II ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schläfli notation {4³}2{4⁴; 6²}4{4⁶; 6⁶; 8³}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L² ligand, giving a 3D framework with a {3⁴; 5⁴} {3²;4;5⁶;6⁶} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a -J₁J₁J₂- coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J₁=−2.77, J₂=−0.67 cm⁻¹. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J₁=−2.05 and J₂=0.55 cm⁻¹, which results in a whole antiferromagnetic state.     

A series of novel lanthanide carboxyphosphonates with a 3D framework structure: synthesis, structure, and luminescent and magnetic properties

By introduction of 1,4-benzenedicarboxylic acid as the second organic ligand, a series of novel lanthanide carboxyphosphonates with a 3D framework structure, namely, [Ln(3)(H(2)L)(HL)(2)(bdc)(2)(H(2)O)]·7H(2)O (Ln = La (), Ce (), Pr (), Nd (), Sm (), Eu (), Gd (), Tb (); H(3)L = H(2)O(3)PCH(2)NC(5)H(9)COOH; H(2)bdc = HOOCC(6)H(4)COOH) have been synthesized under hydrothermal conditions. Compounds are isostructural and feature a 3D framework in which Ln(iii) polyhedra are interconnected by bridging {CPO(3)} tetrahedra into 2D inorganic layers parallel to the ab plane. The organic groups of H(2)L(-) are grafted on the two sides of the layer. These layers are further cross-linked by the bdc(2-) ligands from one layer to the Ln atoms from the other into a pillared-layered architecture with one-dimensional channel system along the a axis. The thermal stability of compounds has been investigated. Luminescent properties of compounds , and the magnetic properties of compound have also been studied.     

Magnetic coupling in EE and EO azido-bridged binuclear copper complexes: Synthesis,structure and magnetic studies

Four azide bridged dinuclear copper(II) complexes, [Cu₂(L^X)₂(N₃)₂](ClO₄)₂, with L^X = substituted N,N-bis[(3,5-dimethylpyrazole-1-yl)-methyl]benzylamine, [X = H (1), OMe (2), Me (3) and Cl (4)] have been synthesized, out of which complexes 1 and 2 have been characterized structurally. In Complex 1 the two bridging azide ligands have connected the two metal centers in an end-on (EO) fashion with aSP (asymmetric Square Pyramidal) geometry and showed an weak antiferromagnetic interaction (J = −3.34 cm⁻¹). On the contrary, in complex 2, the two metal centers have been connected in end-to-end (EE) fashion exhibiting moderately strong ferromagnetic interaction (J = +19.7 cm⁻¹). Cyclic voltammetric studies performed on all the four complexes show a reasonably good correlations when E_1/2 for Cu^IICu^II → Cu^IICu^III and Cu^IICu^III → Cu^IIICu^III oxidations are plotted against σ (substituent constants) with ρ = −0.182 (R² = 0.92) and −0.684 (R² = 0.99) respectively.     

Hydrothermal synthesis, crystal structure and magnetic property of oxalate-bridged iron 1D chain coordination polymer

A novel oxalate-bridged iron coordination polymer, Fe₂(phen)₂(C₂O₄)₂ (1) has been hydrothermally synthesized and characterized by elemental analyses, IR spectrum, TGA-DTA analysis, and single-crystal X-ray diffraction. Compound (1) crystallizes in the monoclinic system, space group P2(1), the final R is 0.0486. The tetradentate-chelating coordination mode of oxalate anion creates an infinite 1D iron (II) oxalate chain structure and from which a 2D network is constructed by π–π interactions of phen rings. The temperature-dependent magnetic susceptibility measurement indicates the existence of a weak antiferromagnetic coupling between Fe^II ions.     

A manganese(II) coordination polymer with a 3D porous structure: Synthesis,structure, and spectroscopic and magnetic behaviour

A manganese(II) complex with N,N′-bis(carboxymethyl)dithiooxamide (H₄GLYDTO), [Mn(H₂GLYDTO)(H₂O)₂]_n, has been synthesized and characterized by elemental analysis and thermogravimetric analysis, as well as by infrared, electronic and EPR spectroscopy and magnetic susceptibility measurements. The crystal and molecular structure of this complex was determined by single-crystal X-ray structure analysis. The compound shows a 3D porous framework with alternate left- and right-handed helical channels where the manganese(II) ions have an octahedral environment. Variable temperature magnetic measurements reveal the existence of very weak antiferromagnetic interactions through the syn-anti carboxylate bridge, with an exchange parameter of J/k = −0.12 K.     

A novel two-dimensional Ni(II) fumarato complex: Solvothermal synthesis, crystal structure and magnetic properties

Dark green single crystals of [Ni(fum)(phen)] (fum = fumarato, phen = 1,10-phenanthroline) (1) have been prepared under solvothermal conditions. Its crystal structure exhibits two dimensional (2D) character. The formed layers are built of dimers of crystallographically non-equivalent Ni(II) atoms linked by bridging fumarato ligands; one is of the μ₄-bridge type with both carboxylato groups coordinated in syn-anti fashion while in the second one both carboxylate groups form a chelate-like coordination. Both Ni(II) atoms are hexa-coordinated in the cis-NiO₄N₂ form; two coordination positions are occupied by a N-bonded chelate phen molecule and four positions by oxygen atoms from the fum ligands. The layers are interconnected by π–π interactions operating between aromatic rings of the phen ligands. The analysis of the experimental thermodynamic data supports the structural assumptions and showed that magnetic subsystem of 1 can be approximated by an array of antiferromagnetic S = 1 dimers with easy-axis uniaxial magnetic anisotropy D comparable to intradimer exchange coupling J, D/J ≈ 1 and D/k_B = −6 K. The specific heat data clearly indicate the absence of a phase transition to the ordered state at least at temperatures down to 2 K.     

Hydrothermal synthesis,crystal structure,and properties of a novel magnesium phosphonate with a 1D chain structure

A novel 1D chain magnesium phosphonate with a 1D channel system along the c-axis, [Mg(H₄L)(H₂O)₃]_n (1) (H₄L^2-=HN(CH₂PO₃H)₃)^2-, has been synthesized under hydrothermal condition using triphosphonate ligand. The MgO₆ polyhedra and NC₃ planes are connected by phosphonate groups to form a 1D chain. The chains are interlinked by hydrogen bonds into 2D layers. Adjacent layers are further linked via hydrogen bonds to build a 3D network structure. The luminescent property of complex 1 has been also studied. For the complex 1, a blue fluorescent emission band with a maximum peak at 460 nm was observed.     

Heterotrimetallic 4f-3d coordination polymers: synthesis, crystal structure, and magnetic properties

A series of cyano-bridged heterotrimetallic complexes [CuL](2)Ln(H(2)O)(2)M(CN)(6).7H(2)O have been synthesized by the reactions of CuL (L(2)(-) = dianion of 1,4,8,11-tetraazacyclotradecane-2,3-dione), Ln(3+) (Ln = Gd or La), and [M(CN)(6)](3)(-) (M = Co, Fe, or Cr). X-ray diffraction analysis reveals that these complexes are isostructural and have a novel chain structure. The Ln(3+) ion is eight-coordinated by six oxygen atoms of two CuL and two water molecules and two nitrogen atoms of the bridging cyano ligands of two [M(CN)(6)](3)(-), while the [M(CN)(6)](3)(-) anion connects two Ln(3+) using two trans-CN(-) ligands giving rise to a chainlike structure. In the chain, every CuL group tilts toward the CN(-) ligand of adjacent [M(CN)(6)](3)(-) with the Cu-N(cyano) contacts ranging from 2.864(6) to 2.930(6) A. Magnetic studies on the CuGdCo complex (1) indicate the presence of ferromagnetic coupling between Cu(II) and Gd(III). The CuLaCr (5) and CuLaFe (2) complexes exhibit ferromagnetic interaction between paramagnetic Cu(II) and Cr(III)/Fe(III) ions through the weak cyano bridges (Cu-N(cyano) = 2.930(6) A for 2). A global ferromagnetic interaction is operative in the CuGdFe complex (3) with the concurrence of dominant ferromagnetic Cu(II)-Gd(III) and minor antiferromagnetic Gd(III)-Fe(III) as well as the ferromagnetic Cu(II)-Fe(III) interaction. For the CuGdCr complex (4), an overall antiferromagnetic behavior was observed, which is attributed to the presence of dominant antiferromagnetic Cr(III)-Gd(III) coupling and the minor ferromagnetic Cu(II)-Gd(III) and Cu(II)-Cr(III) interaction. Moreover, a spin frustration phenomenon was found in complex 4, which results from the ferro-ferro-antiferromagnetic exchanges in the trigonal Cu-Gd-Cr units. The magnetic susceptibilities of these complexes were simulated using suitable models. The magneto-structural correlation was investigated. These complexes did not show a magnetic phase transition down to 1.8 K.     

Synthesis,crystal structure and magnetic properties of 2D bi-layered coordination polymer

A new coordination polymer, [Ni(pydc)(H₂O)₂]?·?H₂O (1) (H₂pydc?=?pyridine-3,4-dicarboxylic acid), have been synthesized by treating Ni(II) nitrate with 3,4-pyridinedicarboxylic acid under hydrothermal conditions. The single-crystal X-ray structure reveals that 1 is a 2D bi-layered coordination polymer. Single-crystals are triclinic, space group P 1 , with a?=?7.065(3), b?=?7.812(4), c?=?9.031(4)?Å, α?=?75.568(8), β?=?68.970(8), γ?=?75.927(8)°, V?=?444.0(3)?ų, Z?=?2. Variable temperature magnetic susceptibility measurements demonstrate a ferromagnetic interaction in 1.