Novel hydrogen-bonded three-dimensional networks encapsulating one-dimensional covalent chains: [M(4,4'-bipy)(H2O)(4)](4-abs)(2).nH2O (4,4'-bipy = 4,4'-bipyridine; 4-abs = 4-aminobenzenesulfonate) (M = Co,n = 1; M = Mn,n = 2)

Two novel compounds, [Co(4,4'-bipy)(H(2)O)(4)](4-abs)(2).H(2)O (1) and [Mn(4,4'-bipy)(H(2)O)(4)](4-abs)(2).2H(2)O (2) (4,4'-bipy = 4,4'-bipyridine; 4-abs = 4-aminobenzenesulfonate), have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analyses, UV-vis and IR spectra, and TG analysis. X-ray structural analysis revealed that 1 and 2 both possess unusual hydrogen-bonded three-dimensional (3-D) networks encapsulating one-dimensional (1-D) covalently bonded infinite [M(4,4'-bipy)(H(2)O)(4)](2+) (M = Co, Mn) chains. The 4-abs anions in 1 form 1-D zigzag chains through hydrogen bonds. These chains are further extended through crystallization water molecules into 3-D hydrogen-bonded networks with 1-D channels, in which the [Co(4,4'-bipy)(H(2)O)(4)](2+) linear covalently bonded chains are located. Crystal data for 1: C(22)H(30)CoN(4)O(11)S(2), monoclinic P2(1), a = 11.380(2) A, b = 8.0274(16) A, c = 15.670(3) A, alpha = gamma = 90 degrees, beta = 92.82(3) degrees, Z = 2. Compound 2 contains interesting two-dimensional (2-D) honeycomb-like networks formed by 4-abs anions and lattice water molecules via hydrogen bonding, which are extended through other crystallization water molecules into three dimensions with 1-D hexagonal channels. The [Mn(4,4'-bipy)(H(2)O)(4)](2+) linear covalent chains exist in these channels. Crystal data for 2: C(22)H(32)MnN(4)O(12)S(2), monoclinic P2(1)/c, a = 15.0833(14) A, b = 8.2887(4) A, c = 23.2228(15) A, alpha = gamma = 90 degrees, beta = 95.186(3) degrees, Z = 4.     

Synthesis and characterization of (smif)2M(n) (n = 0, M = V, Cr, Mn, Fe, Co, Ni, Ru; n = +1, M = Cr, Mn, Co, Rh, Ir; smif =1,3-di-(2-pyridyl)-2-azaallyl)

A series of Werner complexes featuring the tridentate ligand smif, that is, 1,3-di-(2-pyridyl)-2-azaallyl, have been prepared. Syntheses of (smif)(2)M (1-M; M = Cr, Fe) were accomplished via treatment of M(NSiMe(3))(2)(THF)(n) (M = Cr, n = 2; Fe, n = 1) with 2 equiv of (smif)H (1,3-di-(2-pyridyl)-2-azapropene); ortho-methylated ((o)Mesmif)(2)Fe (2-Fe) and ((o)Me(2)smif)(2)Fe (3-Fe) were similarly prepared. Metatheses of MX(2) variants with 2 equiv of Li(smif) or Na(smif) generated 1-M (M = Cr, Mn, Fe, Co, Ni, Zn, Ru). Metathesis of VCl(3)(THF)(3) with 2 Li(smif) with a reducing equiv of Na/Hg present afforded 1-V, while 2 Na(smif) and IrCl(3)(THF)(3) in the presence of NaBPh(4) gave [(smif)(2)Ir]BPh(4) (1(+)-Ir). Electrochemical experiments led to the oxidation of 1-M (M = Cr, Mn, Co) by AgOTf to produce [(smif)(2)M]OTf (1(+)-M), and treatment of Rh(2)(O(2)CCF(3))(4) with 4 equiv Na(smif) and 2 AgOTf gave 1(+)-Rh. Characterizations by NMR, EPR, and UV-vis spectroscopies, SQUID magnetometry, X-ray crystallography, and DFT calculations are presented. Intraligand (IL) transitions derived from promotion of electrons from the unique CNC(nb) (nonbonding) orbitals of the smif backbone to ligand π*-type orbitals are intense (ε ≈ 10,000-60,000 M(-1)cm(-1)), dominate the UV-visible spectra, and give crystals a metallic-looking appearance. High energy K-edge spectroscopy was used to show that the smif in 1-Cr is redox noninnocent, and its electron configuration is best described as (smif(-))(smif(2-))Cr(III); an unusual S = 1 EPR spectrum (X-band) was obtained for 1-Cr.     

Infinite Three-Dimensional Coordination Polymers: Synthesis and Structures of [Cd (4,4'-bpy)2 (H2O)2]n (pic)2n, [Zn (4,4'-bpy)2 (H2O)2 ]n-(pic)2n (H2O)2n, and [Zn (4,4'-bpy)2 (H2O)2]n (4,4'-bpy)n (H2O)n (pic)2n

Recently, a new research realm in crystal engineering of supramolecular architecturesassembled by means of coordinate covalent bonding', hydrogen bonding', or other weakintermolecular interactions= has been rapidly expanding in order to rationally developnew classes of functional materials with cavities or pores. These types of compoundsmay exhibit interesting topological structures and the clathrations of the cavity structuresmay have many potential properties such as catalysis', electrical co…     

Biferrocene-M(mnt)2 charge-transfer complexes (M = Ni, Co; mnt = maleonitriledithiolate). structure, valence states, and magnetic properties

Charge-transfer salts of branched-alkyl biferrocenes, (1',1' '-R2-1,1' '-biferrocene)[Ni(mnt)2] (1a, R = isopropyl; 2a, R = dineopentyl) and (1',1' '-R2-1,1' '-biferrocene)2[Co(mnt)2]2 (1b, R = isopropyl; 2b, R = dineopentyl), were prepared. Their valence states were investigated using X-ray crystallography and M?ssbauer spectroscopy. Complexes 1a and 1b show segregated-stack crystal structures that contain columns of acceptors, whereas structures of 2a and 2b, which contain bulky donors, are rather discrete. All of the complexes contain mixed-valent biferrocenium monocations. A two-step valence transition was found in complex 1a. The crystal contains two crystallographically independent cations: one undergoes valence localization below room temperature; the other undergoes valence localization below ca. 130 K. The former transition is derived from asymmetry of the crystal environment around the cation, whereas the latter one is caused by symmetry lowering coupled with a spin-Peierls transition (T(C) = 133.2 K) associated with the dimerization of the acceptors. This compound was found to exhibit a dielectric response based on valence tautomerization. Other complexes (1b, 2a, and 2b) show a valence-trapped state. In all complexes, charge localization was found to occur through local electrostatic interactions between the donor's cationic moiety and the acceptor's electronegative moieties.     

Weak M(II)-azide-4,4'-bipy ferromagnets based on unusual diamondoid (M = Mn) and 2D arrays (M = Co, Ni)

Four compounds of general formula [M(4,4'bipy)(N(3))2](n) (M = Mn (1), Zn (2), Co (3), Ni (4)) have been synthesized and magnetostructurally characterized by means of X-ray diffraction analysis, IR and ESR spectroscopies, and measurements of the magnetic susceptibility and magnetization. Compound 1 (C(10)H(8)N(8)Mn) crystallizes in the tetragonal P4(3)2(1)2 space group, Z = 4, with a = 8.229(2), b = 8.229(2), and c = 16.915(2) A. It exhibits an acentric 3D structure where Mn(II) ions are linked through EE-azide groups resulting in a diamondoid network. The 4,4'bipy ligands are coordinated on the axial positions of the octahedral spheres reinforcing the intermetallic connections. Weak ferromagnetism arising from spin canting is observed for compound 1. Compounds 2, 3, and 4 are proposed to be isomorphous and would consist of a 2D array where alternating EO + EE/EO + EE/EO + EO azide-chains are linked by 4,4'bipy ligands resulting in pi-pi stacked pyridyl-columns. The azido ligand dispositions in compounds 3 and 4 make possible systems of type -AF-AF-F-, which would give rise to a topological ferromagnetic behavior.     

Favorable hydrogen storage properties of M(HBTC)(4,4'-bipy).3DMF (M = Ni and Co)

Two metal-organic frameworks of M(HBTC)(4,4'-bipy).3DMF (M = Ni and Co; H 3BTC = 1,3,5-benzenetricarboxylic acid; 4,4'-bipy = 4,4'-bipyridine; DMF = N,N'-dimethylformamide) were synthesized by a one-pot solution reaction and a solvothermal method, respectively. The as-prepared samples have high specific surface areas of 1590 m (2)/g and 887 m (2)/g. The activation at different temperatures for the guest removal prior to gas loading obviously affects the gas sorption process. Ni(HBTC)(4,4'-bipy).3DMF shows high hydrogen storage capacities of 1.20 wt % at room temperature and 3.42 wt % at 77 K. Co(HBTC)(4,4'-bipy).3DMF shows capacities of 0.96 wt % at 298 K and 2.05 wt % at 77 K. The hydrogen adsorption heats in the two compounds decrease slightly as a function of the amount adsorbed, and it confirms that the H 2 molecules are combined with stronger sites preferentially. Research on the kinetics of hydrogen adsorption shows a fast saturation process (80 s) and no obvious capacity loss after 20 cycles.     

Kinetics and Mechanism of the Thermal Decomposition of M(NO3)2·nH2O (M=Cu,Co, Ni)

This paper presents the results of simultaneous DTA-TG-DTG and DSC studies on the thermal decomposition of Cu(NO3)2·3H2O, Co(NO3)2·6H2O and Ni(NO3)2·6H2O in an air atmosphere. The mechanism and enthalpies of the investigated processes were determined, as well as the kinetic parameters of the processes run under non-isothermal conditions by means of Kissinger's method. The dependence of the activation energy on the ionic radius of the cations building up the crystal lattices of the investigated compounds was also studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Strong electron-accepting methylviologen dication confined in magnetic hosts: synthesis, structural characterization, charge-transfer and magnetic properties of {(MV)2[Ni(SCN)5].Cl.2H2O}n and {(MV)[m(N3)2(SCN)2]}n (M=Mn, Co)

Three hybrid host-guest compounds {(MV)2[Ni(SCN)5].Cl.2H2O}n (1), {(MV)[Mn(N3)2(SCN)2]}n (2) and {(MV)[Co(N3)2(SCN)2}n (3) (where MV2+ = methylviologen dication) have been obtained by self-assembly methods and characterized by X-ray crystallography, spectral methods and magnetic measurements. Compound 1 shows a quasi-two-dimensional structure which is formed by novel single thiocyanate-bridged Ni(II) chains connected through S...S interactions. Compounds 2 and 3 are isostructural, containing single micro(1,3)-azide bridged Mn(II)/Co(II) square layers. MV2+, as a strong electron-acceptor and a template, is embedded between the anionic layers in all three compounds. The charge-transfer (CT) interactions between MV2+ and the anionic hosts have been revealed by structural analysis and UV-vis diffuse reflection spectroscopy. The magnetic studies of the compounds show antiferromagnetic interactions between adjacent metal ions (J = -34.52(7) cm(-1) for 1, J = -3.90(2) cm(-1) for 2 and J = -10.96(6) cm(-1) for 3).     

Synthesis, magnetic properties, and magnetic structure of a natrochalcite structural variant, KM(II)2D3O2(MoO4)2 (M = Mn, Fe, or Co)

We report the syntheses, crystal structures, and magnetic properties of KMn(2)(H(3)O(2))(MoO(4))(2) (MnH), KMn(2)(D(3)O(2))(MoO(4))(2) (MnD), KFe(2)(H(3)O(2))(MoO(4))(2) (FeH), KFe(2)(D(3)O(2))(MoO(4))(2) (FeD), KCo(2)(H(3)O(2))(MoO(4))(2) (CoH), and KCo(2)(D(3)O(2))(MoO(4))(2) (CoD), and the magnetic structures of MnD and FeD. They belong to the structural variant (space group I2/m) of the mineral natrochalcite NaCu(2)(H(3)O(2))(SO(4))(2) (space group C2/m) where the diagonal within the ac-plane of the latter become one axis of the former. The structure of MnD, obtained from Rietveld refinement of a high-resolution neutron pattern taken at 300 K, consists of chains of edge-sharing octahedra bridged by MoO(4) and D(3)O(2) to form layers, which are connected to K through the oxygen atoms to form the three-dimensional (3D)-network. The X-ray powder diffraction patterns of the other two compounds were found to belong to the same space group with similar parameters. The magnetic susceptibilities of MnH and FeH exhibit long-range ordering of the moments at a Ne?el temperature of 8 and 11 K, respectively, which are accompanied by additional strong Bragg reflections in the neutron diffraction in the ordered state, consistent with antiferromagnetism. Analyses of the neutron data for MnD and FeD reveal the presence of both long- and short-range orderings and commensurate magnetic structures with a propagation vector of (?, 0, ?). The moments are antiferromagnetically ordered within the chains with alternation between chains to generate four nonequivalent nuclear unit cells. For MnD the moments are perpendicular to the chain axis (b-axis) while for FeD they are parallel to the b-axis. The overall total is a fully compensated magnetic structure with zero moment in each case. Surprisingly, for KCo(2)(D(3)O(2))(MoO(4))(2) neither additional peaks nor increase of the nuclear peaks' intensities were observed in the neutron diffraction patterns below the magnetic anomaly at 12 K which was identified to originate from a small quantity of a ferromagnetic compound, Co(2)(OH)(2)MoO(4).     

Thermochemistry of AII(VUO6)2 · nH2O Compounds (AII = Mn, Fe, Co, Ni, Cu, Zn, Cd)

Standard enthalpies of formation of uranovanadates of 3(4)d transition metals at 298.15 K were determined. The isobaric heat capacity of Co(VUO₆)₂ · 4H₂O was measured. The standard Gibbs functions of formation of the compounds were calculated on the basis of these data using approximate methods of absolute entropy calculation. The thermochemical characteristics of the synthesis and dehydration of uranovanadates were considered.     

Monodisperse MFe2O4 (M = Fe, Co, Mn) nanoparticles

High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)(3), with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe(3)O(4)) nanoparticles. Similarly, reaction of Fe(acac)(3) and Co(acac)(2) or Mn(acac)(2) with the same diol results in monodisperse CoFe(2)O(4) or MnFe(2)O(4) nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe(3)O(4) can be oxidized to Fe(2)O(3), as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.     

Structural and magnetic properties of MCl2 (M = Fe, Mn, Co): acetonitrile solvates

MIICl2 (M = Mn, Fe, Co) as their acetonitrile solvates were isolated, and their structural, spectroscopic, and magnetic properties were studied. MCl2(NCMe)2 (M = Fe, Mn) form 1-D chains of octahedral MII ions with four bridging chlorides and two axial MeCN's. The presence of an axial distortion for MFe causes a significant magnetic anisotropy that increases significantly below 150 K; however, chiav [=(chi parallel + 2chi perpendicular)/3] almost coincides with the value obtained on a polycrystalline sample. MnCl2(NCMe)2 is a paramagnet with a weak antiferromagnetic coupling. Annealing FeCl2(NCMe)2 at 55 degrees C forms the monosolvate of FeCl2(NCMe) composition in which two chains collapse into a double chain with formation of Fe-Cl bonding such that half of the mu-Cl's becomes mu3-Cl's. This material orders magnetically below Tc = 4.3 K. For M = Co, paramagnetic tetrahedral [CoCl3(NCMe)]- anions are isolated.     

Three banana-shaped arsenomolybdates encapsulating a hexanuclear transition-metal central magnetic cluster: [As(III)2Fe(III)5MMo22O85(H2O)]n- (M = Fe3+, n = 14; M = Ni2+ and Mn2+, n = 15)

Three polyoxometalates encapsulating high-nuclearity magnetic clusters MFe(5), [As(2)MFe(5)Mo(22)O(85)(H(2)O)](n-) (M = Fe(3+), n = 14; M = Ni(2+) and Mn(2+), n = 15), were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, and magnetism measurements. The polyanion [As(2)MFe(5)Mo(22)O(85)(H(2)O)](n-) consists of a central MMo(7)O(28) (M = Fe(3+), Ni(2+), and Mn(2+)) fragment and two AsMo(7)O(27) fragments linked together by two trimeric clusters, Fe(2)MoO(μ(2)-O)(2) and Fe(3)(H(2)O), to form a banana-shaped structure with C(1) symmetry. The MMo(7)O(28) and AsMo(7)O(27) units have a similar structure and can be considered as a monocapped hexavacant α-B-Keggin subunit with a central MO(4) group or a central As(III)O(3) group. The polyoxometalates have a low absorption of υ(Mo-O(d)) (925-913 cm(-1)) because most of the Mo atoms in the polyanions have at least two longer Mo-O(d) bonds. The framework of the arsenomolybdates is stable before As(2)O(3) escaping (ca. 300 °C). The analysis of magnetostructural correlations and magnetism measurements indicate the coexistence of ferro- and antiferromagnetic interactions, which give an overall ferromagnetic spin ground state in the compounds.     

Inorganic-organic framework structures; M(II) ethylenediphosphonates (M = Co, Ni, Mn) and a Mn(II) ethylenediphosphonato-phenanthroline

The reaction of nickel, cobalt, and manganese with 1,2-ethylenediphosphonic acid or 1,2-ethylenediphosphonic acid and 1,10-phenanthroline under hydrothermal conditions resulted in the pillared layered structures Co2(H2O)2(O3PC2H4PO3) (I) and Ni2(H2O)2(O3PC2H4PO3) (II), which are isostructural to a zinc phase that has previously been characterized by X-ray powder methods. In addition, a 1D chain structure, Mn(HO3P(CH2)2PO3H)(H2O)2(C12H8N2) (III), and a pillared layered structure, Mn(HO3P(CH2)2PO3H) (IV), were obtained. The structures of these phases were solved by single-crystal X-ray diffraction methods. The crystallographic data are as follows: compound I P21/n (No. 14), a = 5.6500(11) A, b = 4.7800(10) A, c = 15.330(3) A, beta = 98.50(3) degrees, V = 409.47(14) A3, Z = 2; compound II P21/n (No. 14), a = 5.5807(11) A, b = 4.7205(9) A, c = 15.250(3) A, beta = 98.55(3) degrees, V = 397.28(13) A3, Z = 2; compound III C2/c (No. 15), a = 12.109(2) A, b = 15.328(3) A, c = 9.848(2) A, beta = 108.88(3) degrees, V = 1729.5(6) A3, Z = 4; compound IV P (No. 2), a = 5.498(5) A, b = 7.715(6) A, c = 8.093(7) A, alpha = 82.986(12) degrees, beta = 75.565(12) degrees, gamma = 80.582(12)degrees, V = 326.7(5) A3, Z = 2. Magnetic measurements show antiferromagnetic behavior below TN = 7 K for I and 13 K for II.     

Preparation of ferrite MFe2O4 (M = Co, Ni) ribbons with nanoporous structure and their magnetic properties

Spinel ferrite, MFe 2O 4 (M = Co, Ni), ribbons with nanoporous structure were prepared by electrospinning combined with sol-gel technology. The ribbons were formed through the agglomeration of magnetic nanoparticles with PVP as the structure directing template. The length of the polycrystalline ribbons can reach millimeters, and the width of the ribbons can be tuned from several micrometers to several hundred nanometers by changing the concentration of precursor. The nanoporous structure was formed during the decomposition of PVP and inorganic salts. The ribbons exhibited weak saturation magnetizations and low coercivities at room temperature, but at low temperature, saturation magnetizations and coercivities increased a lot, especially for CoFe 2O 4 ribbons, reaching 72 emu/g and 1.45 T at 2 k, respectively. These novel magnetic ribbons can potentially be used in micro/nano electronic devices, gas-sensors, and catalysts.     

Supramolecular motifs and solvatomorphism within the compounds [M(bpy)3]2[NbO(C2O4)(3)]Cl.nH2O (M = Fe2+, Co2+, Ni2+, Cu2+ and Zn2+; n = 11, 12). Syntheses, structures and magnetic properties

Solvatomorphism has been found between two series of complexes of the composition [M(bpy)3]2[NbO(C2O4)3]Cl.nH2O [M = Fe2+ (1, 2), Co2+ (3, 4), Ni2+ (5, 6), Cu2+ (7) and Zn2+ (8, 9); bpy = 2,2'-bipyridine)], crystallizing in the monoclinic space group P2 1/c [3, 5, 8 (n = 11)] or in the orthorhombic space group P21 21 21 [2, 4, 6, 7 (n = 12)]. All the structures contain two symmetry independent [M(bpy)3]2+ cations, one [NbO(C2O4)3]3- anion, one Cl(-) anion, and crystal water molecules. The cations possess a trigonally distorted octahedral geometry, with an additional tetragonal distortion in 7. Analysis of crystal packing reveals a specific type of supramolecular contact comprising four bipyridine ligands from two neighbouring [M(bpy)3]2+ cations--quadruple aryl embrace (QAE) contact. The contact is realized by the alignment of two molecular two-fold rotation axes, preserving the parallel orientation of the molecular three-fold rotation axes. The resulting two-dimensional honeycomb lattices of [M(bpy)3]2+ cations are placed between the hydrogen bonding layers made of [NbO(C2O4)3]3- and Cl(-) anions and the majority of the crystal water molecules. The temperature-dependent magnetic susceptibility measurements (1.8-300 K) show a significant orbital angular momentum contribution for 3 and 4 (high-spin Co2+), the influence of zero-field splitting for 5 and 6(Ni2+) and a substantially paramagnetic Curie behaviour for the Cu2+ compound (7).     

Crystal and magnetic structures and magnetic properties of selenate containing natrochalcite, A(I)M(II)2(H3O2)(SeO4)2 where A = Na or K and M = Mn, Co, or Ni

The synthesis of a series of selenate containing natrochalcite, A(I)M(II)(2)(H(3)O(2))(SeO(4))(2) where A = Na or K and M = Mn, Co, or Ni (here labeled as AMH and AMD for the hydrogenated and deuterated compounds, respectively), the X-ray crystal structure determinations from single crystals (Ni) and powder (Mn), magnetic properties, and magnetic structures of the cobalt analogues are reported. The nuclear crystal structures for NaNiH, KNiH, and KMnH are similar to those reported for the cobalt analogues (NaCoH and KCoH) and consist of chains of edge-sharing octahedra (MO(6)) which are connected by H(3)O(2) and SeO(4) to form layers which are in turn bridged by the alkali, in an octahedral coordination site, to form the 3D-framework. The magnetic properties are characterized by antiferromagnetic interaction at high temperatures and antiferromagnetic ordering at low temperatures (NaCoH, 3.5 K; KCoH, 5.9 K; KNiH, 8.5 K; and KMnH, 16 K), except for KNi(2)(H(3)O(2))(SeO(4))(2) which displays a weak ferromagnetic interaction and no long-range ordering above 2 K. The neutron magnetic structures of the cobalt analogues, studied as a function of temperature, are different for the two cobalt salts and also different from all the known magnetic structures of the natrochalcite family. Whereas the magnetic structure of NaCoD has a k = (0, 0, 0), that of KCoD has one consisting of a doubled nuclear cell, k = (0, 0, 1/2). Both compounds have four magnetic sublattices related to the four cobalt atoms of the nuclear unit cell. In NaCoD the moments are in the bc-plane, M(y) = 2.51(2) μ(B) and M(z) = 1.29(4) μ(B), with the major component along the cobalt chain and the resultant moment, 2.83(3) μ(B), making an angle of 27° with the b-axis. The sum of the moments within the cell is zero. For KCoD the moment at each cobalt site has a component along each crystallographic axis, M(x) = 2.40(3), M(y) = 1.03(3), M(z) = 1.59(8) giving a total M = 2.49(3) μ(B). Within one nuclear cell the moments are fully compensated. The moments corresponding to the cobalt atoms of the second nuclear cell comprising the magnetic unit cell are oriented in opposite directions.