A new type of anionic metal dicyanamide extended networks through [Cu(N4-macrocycle)]2+ cation templation. Structure and magnetic properties

Two isomorphous anionic metal dicyanamide extended systems [Cu(pCTH)][M(dca)(4)] (M = Mn(II), Co(II); dca = dicyanamide; pCTH = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetrazacyclotetradecane-4,11-diene) have been prepared through [Cu(pCTH)](2+) templation and characterized by X-ray crystallography and magnetic measurements. In these complexes, the [M(dca)(4)](2)(-) anions form 2D (4,4) distorted square-gridlike sheets in which each elongated octahedral M(N(dca))(6) metal center is connected to four neighboring ones through single dicyanamide bridges in equatorial positions. [Cu(pCTH)](2+) cations lie between the sheets and display weak bonding interactions with the axial dicyanamide ligands on the M centers of two neighboring [M(dca)(4)](n)()(2)(n)()(-) sheets, thus leading to a 3D heterometallic network. Variable-temperature magnetic measurements reveal weak antiferromagnetic interactions between metal centers across mu(1,5)-dicyanamide bridging ligands. For the cobalt(II) compound, the experimental data for T > 30 K match well with the calculated curve by taking into consideration the spin-orbit coupling effect for the (4)T(1g) ground state of the cobalt(II) and an axial distortion of the octahedral geometry. No long-range magnetic order was observed in these compounds above 2 K.     

Spin canting in the 3D anionic dicyanamide structure (SPh(3))Mn(dca)(3) (Ph = phenyl, dca = dicyanamide)

Through use of the SPh(3)(+) (Ph = phenyl, C(6)H(5)) cation as a molecular template, a new three-dimensional Mn(dca)(3)(-) [dca = dicyanamide, N(CN)(2)(-)] anionic structure has been crystallized. At room temperature, (SPh(3))Mn(dca)(3) (1) crystallizes in the monoclinic space group P2(1)/c, with a = 11.7079(5) A, b = 12.8554(5) A, c = 16.8605(6) A, beta = 100.666(2) degrees, and V = 2493.8(3) A(3). Magnetic susceptibility measurements indicate that this salt exhibits a spin canted long range antiferromagnetically ordered ground state below 2.5 K.     

Synthesis and Crystal Structure of an Inclusion Compound Constructed through Self-assembly of Nicotinamide and Dicyanamide Coordination Bridges

A novel inclusion compound of [Mn(dca)2(3-nic)2]n·(3-nic)2n(1,dca = dicyanamide,3-nic = nicotinamide) has been prepared and characterized by single-crystal X-ray diffraction,elemental analysis and IR.This complex crystallizes in the triclinic system,space group P1 with a = 7.5979(8),b = 7.7128(9),c = 14.5346(17),α = 100.094(2),β = 92.444(2),γ = 116.736(2)o,V = 741.72(15) 3,Z = 1,Dc = 1.512 g/cm3,Mr = 675.55,μ = 0.507 mm-1,F(000) = 347,S = 1.023,the final R = 0.0400 and wR = 0.1010.The inclusion compound is constructed by a three-dimensional host network that consists of dca,3-nic and Mn2+ with coordination and hydrogen-bonding interactions.In the network,one-dimensional rectangular channels are formed,and the guest molecules(3-nic) are included in the channels.The guest molecules interlink with the host through strong hydrogen bonds.     

Syntheses,Structures and Electrochemistry Properties of Two Dicyanamide Manganese(III) Complexes [Mn(5‐Brsalen)(dca)]·CH3OH and [Mn(3‐Meosalphen)(dca)(H2O)]

Two manganese(III)‐dicyanamide compounds, [Mn(5‐Brsalen)(dca)] · CH₃OH ( 1 ) and [Mn(3‐Meosalphen)(dca)(H₂O)] ( 2 ) (dca = dicyanamide anion, [N(CN)₂]^–), were synthesized and characterized by elemental analysis, IR spectroscopy, single‐crystal X‐ray structure analysis, and cyclic voltammetry. The structure of complex 1 is an infinite zigzag chain of hexacoordinate Mn^III ions, in which the adjacent manganese atoms are connected by dca in μ_1,5‐bridging mode. The molecular structure of complex 2 consists of a hexacoordinate Mn^III atom, which generates a slightly distorted octahedral arrangement, and a dimer structure is formed by intermolecular hydrogen bonding interactions. The electrochemical properties of the two complexes were measured by cyclic voltammetry.     

Entrapment of [Ru(bpy)3]2+ in the anionic metal-organic framework: novel photoluminescence behavior exhibiting dual emission at room temperature

[Ru(bpy)(3)](2+) (bpy = 2,2'-bipyridine) ions were entrapped into the cavities of two-dimensional anionic sheet-like coordination polymeric networks of [M(dca)(3)](-) (dca = dicyanamide; M = Mn(II) and Fe(II)). The prepared compounds, {[Ru(bpy)(3)][Mn(dca)(3)](2)}(n) (1) and {[Ru(bpy)(3)][Fe(dca)(3)](2)}(n) (2), were structurally characterized by X-ray single crystal analysis. The spectroscopic properties of the [Ru(bpy)(3)](2+) ion dramatically changed on its entrapment in [M(dca)(3)](-). The [Ru(bpy)(3)](2+) moiety present in 1 and 2 exhibits novel dual photo-emission at room temperature.     

Synthesis, structure, and magnetism of bimetallic manganese or nickel complexes of a bridging verdazyl radical

Two binuclear metal-radical complexes, formed by the reaction of M(hfac)(2) x 2H(2)O (M = Mn or Ni; hfac = hexafluoroacetylacetonate) with the 1,5-dimethyl-3-(4,6-dimethylpyrimidin-2-yl)-6-oxoverdazyl radical (3), were synthesized. The binuclear Mn complex 5 (i.e., 3[Mn(hfac)(2)](2)) crystallizes in the monoclinic space group C2/c: C(30)H(17)N(6)O(9)F(24)Mn(2), a = 29.947(3), b = 17.143(3), c = 16.276(3) A, beta = 123.748(3)*, Z = 4. The compound consists of two pseudo-octahedral Mn(II) ions, both bearing two hfac ancillary ligands, bridged by the bis(bidentate) radical 3. The temperature dependence of the magnetic susceptibility of 5 reveals moderate antiferromagnetic exchange between each of the Mn(II) ions and the verdazyl radical (J = -48 cm(-1)). The S = 9/2 ground spin state of the complex was corroborated by low-temperature magnetization versus field measurements. In contrast, the magnetic susceptibility versus temperature behavior of 6 (whose molecular structure is presumed to be analogous to that of 5) indicates that the two Ni(II) ions are strongly ferromagnetically coupled to the verdazyl radical (J = +220 cm(-1)). The magnetization versus field behavior of 5 is consistent with an S = 5/2 ground-state species.     

Self-penetration--a structural compromise between single networks and interpenetration: magnetic properties and crystal structures of

The three-dimensional coordination polymers [Mn(dca)2(H2O)] (1) and [M(dca)(tcm)], M =Co (2), Ni (3), Cu (4), dca =dicyanamide, N(CN)2-, tcm = tricyanomethanide, C(CN)3-, have isomorphous structures. In 1 half the dca ligands coordinate directly (through all three nitrogen atoms) to three Mn atoms (all metal atoms are six-coordinate), while the other half coordinate to two Mn atoms (through the nitrile nitrogens) and hydrogen bond to water molecules coordinated to a third Mn atom (through the amide nitrogen). This dca. H2O structural moiety is disordered over a mirror plane, and is replaced by the structurally equivalent tcm ligand in compounds 2-4. The resulting structures display a new self-penetrating 3,6-connected (2:1) network topology that can be related to, but is different from, the rutile net. The self-penetrating [M(dca)(tcm)] network can be viewed as a structural compromise between the two interpenetrating rutile-like networks of [M(tcm)2] and the single rutile-like network of alpha-[M(dca)2]. The temperature and field dependence of the DC and AC magnetic susceptibilities and magnetisations has been measured for complexes 1-4. Compounds 1-3 exhibit long-range magnetic order with critical temperatures of 6.3 K for 1, 3.5 K for 2 and 8.0 K for 3. The Cu11 compound 4 does not order and is essentially a paramagnet. Hysteresis measurements of coercive field and remnant magnetisation show that 1, 2 and 3 are soft magnets, 1 being a canted-spin antiferromagnet (weak ferromagnet), while 2 and 3 are ferromagnets that display some unusual features in their high-field magnetisation isotherms in comparison to their related alpha-[M(dca)2] phases.     

Crystal structures and magnetic properties of 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)-containing copper(II) complexes

Four new copper(II) complexes of formula [Cu(2)(tppz)(dca)(3)(H(2)O)].dca.3H(2)O (1), [Cu(5)(tppz)(N(3))(10)](n)() (2), [[Cu(2)(tppz)(N(3))(2)][Cu(2)(N(3))(6)]](n)() (3), and [Cu(tppz)(N(3))(2)].0.33H(2)O (4) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and dca = dicyanamide anion] have been synthesized and structurally characterized by X-ray diffraction methods. The structure of complex 1 is made up of dinuclear tppz-bridged [Cu(2)(tppz)(dca)(3)(H(2)O)](+) cations, uncoordinated dca anions, and crystallization water molecules. The copper-copper separation across bis-terdentate tppz is 6.5318(11) A. Complex 2 is a sheetlike polymer whose asymmetric unit contains five crystallographically independent copper(II) ions. These units are building blocks in double chains in which the central part consists of a zigzag string of copper atoms bridged by double end-on azido bridges, and the outer parts are formed by dinuclear tppz-bridged entities which are bound to the central part through single end-on azido bridges. The chains are furthermore connected through weak, double out-of-plane end-on azido bridges, yielding a sheet structure. The intrachain copper-copper separations in 2 are 6.5610(6) A across bis-terdentate tppz, 3.7174(5) and 3.8477(5) A across single end-on azido bridges, and from 3.0955(5) to 3.2047(7) A across double end-on azido bridges. The double dca bridge linking the chains into sheets yields a copper-copper separation of 3.5984(7) A. The structure of 3 consists of centrosymmetric [Cu(2)(tppz)(N(3))(2)](2+) and [Cu(2)(N(3))(6)](2)(-) units which are linked through axial Cu.N(azido) (single end-on and double end-to-end coordination modes) type interactions to afford a neutral two-dimensional network. The copper-copper separations within the cation and anion are is 6.5579(5) A (across the bis-terdentate tppz ligand) and 3.1034(6) A (across the double end-on azido bridges), whereas those between the units are 3.6652(4) A (through the single end-on azido group) and 5.3508(4) A (through the double end-to-end azido bridges). The structure of complex 4 is built of neutral [Cu(tppz)(N(3))(2)] mononuclear units and uncoordinated water molecules. The mononuclear units are grouped by pairs to give a rather short copper-copper separation of 3.9031(15) A. The magnetic properties of 1-4 have been investigated in the temperature range 1.9-300 K. The magnetic behavior of complexes 1 and 4 is that of antiferromagnetically coupled copper(II) dimers with J = -43.7 (1) and -2.1 cm(-)(1) (4) (the Hamiltonian being H = -JS(A).S(B)). An overall ferromagnetic behavior is observed for complexes 2 and 3. Despite the structural complexity of 2, its magnetic properties correspond to those of magnetically isolated tppz-bridged dinuclear copper(II) units with an intermediate antiferromagnetic coupling (J = -37.5 cm(-)(1)) plus a ferromagnetic chain of hexanuclear double azido-bridged copper(II) units (the values of the magnetic coupling within and between the hexameric units being +61.1 and +0.0062 cm(-)(1), respectively). Finally, the magnetic properties of 3 were successfully analyzed through a model of a copper(II) chain with regular alternating of three ferromagnetic interactions, J(1) = +69.4 (across the double end-on azido bridges in the equatorial plane), J(2) = +11.2 (through the tppz bridge), and J(3) = +3.4 cm(-)(1) (across the single end-on azido bridge).     

Directed synthesis of μ-1,3,5 bridged dicyanamides by thermal decomposition of μ-1,5 bridged precursor compounds

Reaction of transition-metal dicyanamides with pyridazine leads to the formation of the ligand-rich 1 : 2 (1 : 2 = ratio between metal salt and organic co-ligand) compounds [M(dca)(2)(pydz)(2)](n) (dca = dicyanamide, pydz = pyridazine) with M = Mn (1-Mn), Fe (1-Fe), Co (1-Co), Ni (1-Ni). In their crystal structures linear polymeric M-(dca)(2)-M chains are found, in which the M(ii) cations are μ-1,5 bridged by the dca anions. The pydz ligands are terminally N-bonded to the cations, which are octahedrally coordinated by two pydz ligands and four dca anions. On heating these precursor compounds, 1-Mn, 1-Fe and 1-Co transform quantitatively into new ligand-deficient 1 : 1 intermediate compounds of composition [M(dca)(2)(pydz)](n) with M = Mn (2-Mn), Fe (2-Fe) and Co (2-Co). Investigations by IR spectroscopy, and single crystal X-ray structure analysis, show that the intermediates form a more condensed layered structure in which half of the pristine μ-1,5 bridged dca anions become μ-1,3,5 bridging. This structural transformation is accompanied by a pronounced change of their magnetic properties: whereas the ligand-rich 1 : 2 compounds show only Curie-Weiss paramagnetism, the ligand-deficient 1 : 1 intermediates show either antiferro- or ferromagnetic ordering at lower temperatures mediated by the three-atom pathway of the μ-1,3,5 bridging dca anions.     

Heteronuclear complexes of macrocyclic oxamide with co-ligands: syntheses, crystal structures, and magnetic properties

Four heteronuclear complexes Mn(CuL)2(SCN)2 (1), {[Mn(CuL)2(mu-dca)2].2H2O}n (2), Zn(CuL)2(SCN)2 (3), and [Fe(CuL)(N3)2]2 (4) incorporating macrocyclic oxamide ligands have been synthesized and structurally characterized. L is the dianion of diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]-tetraazacyclotetradecine-13,18-dicarboxylate, and dca is the dicyanamide. The structure of 1 or 3 consists of oxamido-bridged trinuclear [MIICuII2] molecules (for 1, M is the manganese(II) ion, and for 3, M is the zinc(II) ion). Both of them consist of 1D supramolecuar chains via pi-pi interactions. The structure of 2 also has the oxamido-bridged trinuclear [MnIICuII2] structure units and consists of 2D layers formed by the linkage of copper(II) and manganese(II) atoms via the oxamido and mu1, 5-dca bridges. Complex 4 consists of oxamido-bridged tetranuclear [FeII2CuII2] molecules and arranges in 1D chains. Different co-ligands may result in different structures in this macrocyclic oxamide system. The variable-temperature magnetic susceptibility measurements (2-300 K) of 1 and 2 both show the pronounced antiferromagnetic interactions between the copper(II) and manganese(II) ions.     

Mn(dca)2(pym)2 and Mn(dca)2(pym)(H2O) {dca = dicyanamide; pym = pyrimidine}: New coordination polymers exhibiting 1- and 2-D topologies

Two new coordination polymers comprised of Mn(2+), N(CN)(2)(-) (dicyanamide, herein denoted dca) and pyrimidine (pym) have been synthesized and structurally and magnetically characterized. Mn(dca)(2)(pym)(2), , crystallizes in the orthorhombic space group Pbcn and forms trans bi-bridged Mn-(micro(1,5)-dca)(2)-Mn ribbons that extend along the b-axis of the unit cell. Two terminally bonded pym ligands are trans-coordinated to the Mn center. Adjacent chains interdigitate in an undulating fashion presumably due to a templating effect imposed by the pym ligands where N-atoms of consecutive pym rings stack parallel to the chain axis. Mn(dca)(2)(pym)(H(2)O), , which crystallizes in the monoclinic space group P2(1)/c, has a unique interdigitated 2D network that consists of double-bridged [Mn(2)(dca)(2)(pym)(2)(H(2)O)(2)](2+)"dimers" that are connected via single-bridging dca ligands. Each MnN(5)O octahedron is comprised of a coordinated H(2)O, a monodentate pym ligand, and four micro(1,5)-bridging dca anions. The magnetic data for were fitted to a uniform antiferromagnetic chain model which yielded J/k(B) = -0.34(1) K. In contrast, is best described as an alternating chain owing to the presence of both single- and double-bridging dca anions; a least-squares fit afforded J(a) = -0.43(1) and J(b) = -0.20(2) K, respectively. A transition to long-range magnetic ordering was observed for below approximately 2.4 K in addition to a field-induced spin flop transition at 15.6 kOe (1.7 K).     

Structural analysis, spectroscopic, and magnetic properties of the 1D triple-bridged compounds [M(dca)2(bpa)] (M = Mn, Fe, Co, Zn; dca = dicyanamide; bpa = 1,2-bis(4-pyridyl)ethane) and the 3D [Ni(dca)(bpa)2]dca·6H2O

The family of compounds [Mn(dca)(2)(bpa)] (1), [Fe(dca)(2)(bpa)] (2), [Co(dca)(2)(bpa)] (3), [Zn(dca)(2)(bpa)] (4), and [Ni(dca)(bpa)(2)]dca·6H(2)O (5), with dca = dicyanamide and bpa = 1,2-bis(4-pyridyl)ethane, has been synthesized. These compounds have been characterized by single crystal (1, 2, 4, and 5) and powder X-ray diffraction (3), by Fourier transform infrared (FTIR), UV-vis, and electron paramagnetic resonance (EPR) spectroscopies, and by magnetic measurements. Compound 1 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 16.757(6), b = 9.692(3), and c = 13.073(4) ?, and β = 123.02(2)°; Compound 2 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 16.588(5), b = 9.661(3), c = 12.970(5) ?, and β = 123.16(3)°; Compound 4 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 16.519(2), b = 9.643(2), c = 12.943(2) ?, and β = 123.15(1)°; Compound 5 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 18.504(4), b = 19.802(3), and c = 8.6570(18) ?, and β = 99.74(2)°. The compounds 1-4 are isostructural and show a one dimensional (1D) disposition, with the metal(II) ions bridged by double μ(1,5) dca ligands and unusually by a third bridge consisting of the bpa ligand, which adopts a very low torsion angle to accommodate in the structure. This kind of structure is unusual, even considering the voluminous bpa bridge. The compound 5 shows a 3D structure with layers of Ni-bpa joined by single dca bridges. Magnetic susceptibility measurements show antiferromagnetic couplings, increasing for 1-3. Compound 5 shows very slight antiferromagnetic interactions.     

A New One-dimensional Dicyanamide Bridged Zinc(II) Complex Containing Nitronyl Nitroxide Radicals:Synthesis,Crystal Structure and Magnetic Properties

A new one-dimensional dicyanamide bridged zinc(II) complex containing nitronyl nitroxide radicals Zn(NO3)(NIT-1'-MeBzIm)(dca)n·(H2O)n(NIT-1'-MeBzIm = 2-{2'-(l'-me-thyl)benzimidazolyl}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, dca = dicyanamide anion) has been prepared and structurally characterized by single-crystal X-ray diffraction.The complex crystallizes in triclinic, space group P1, with a = 7.428(3), b = 9.839(3), c = 16.708(6), α = 93.270(4), β = 101.642(4), γ = 100.632(4)°, C17.5H21N8O5.5Zn, Mr = 496.79, V = 1169.7(7) 3, Dc = 1.411 g/cm3, μ(MoKα) = 1.096 mm-1, Z = 2, F(000) = 512, R = 0.0583 and wR = 0.1663 for 4295 observed reflections with I > 2σ(I).X-ray analysis reveals that the zinc(II) ion is six-coordinated with a distorted octahedral geometry.These units develop as 1D species where dicyanamide ligands bridge zinc(II) ions.In addition, molecules are linked by π-π piling interactions to form 1-D double-chains.Magnetic investigation indicates that the weak intramolecular interactions are antiferromagnetic with J =-0.27 cm?1, where the spin Hamitonian is defined as H =-2∑i,jJi,jSiS within the complex.     

Structures and magnetic behavior of 1-, 2-, and 3D coordination polymers in the Cu(II)-dicyanamide-pyrimidine family

Using aqueous conditions, three new coordination polymers containing Cu(2+) cations, dicyanamide (dca) anions, and pyrimidine (pym) were isolated and structurally and magnetically characterized. Comprising the bulk of the product yield, Cu(dca)(2)(pym)(2), 1, crystallizes in the monoclinic space group P2(1)/c with a = 7.3569(5) A, b = 13.4482(9) A, c = 7.4559(5) A, beta = 98.984(3) degrees, and V = 728.6(1) A and forms linear 1D chains. The second compound, Cu(dca)(NO(3))(pym)(H(2)O), 2, is also monoclinic, P2(1)/n, with a = 7.6475(3) A, b = 12.2422(5) A, c = 11.0286(4) A, beta = 106.585(2) degrees, and V = 989.6(1) A(3). A 2D network structure consisting of both bridging mu-dca and pym ligands is formed while the NO(3)(-) and H(2)O are axially bonded to the Cu center. Cu(3)(dca)(6)(pym)(2).0.75H(2)O, 3, is triclinic, Ponemacr;, with a = 7.7439(4) A, b = 9.3388(5) A, c = 10.1779(5) A, alpha = 86.014(2) degrees, beta = 88.505(2) degrees, gamma = 73.623(2) degrees, and V = 704.46(9) A(3). The structure of 3 is quite unique in that [Cu(3)(pym)(2)](6+) trimers are interconnected via mu-dca ligands affording a complex 3D self-penetrating framework. Magnetically, 1 exhibits extremely weak exchange interactions along the Cu-(dca)(2)-Cu ribbons while 2 and 3 display very strong magnetic couplings mediated by the mu-bonded pym ligands. Moreover, 2 shows a broad maximum in chi(T) at 40 K and behaves as a uniform 1D antiferromagnetic chain with g = 2.09(1), J/k(B) = -42.6(1) K, and TIP = -66 x 10(-)(6) emu/mol. An S = (1)/(2) trimer model that includes intertrimer interactions successfully described the magnetic behavior of 3, yielding g = 2.10(1), J/k(B) = -69.4(5) K, theta = -0.28(3) K, and TIP = -180 x 10(-)(6) emu/mol. It is found that mu-bonded dca and pym ligands mediate very weak and very strong exchange interactions, respectively, between Cu(2+) centers.     

Synthesis, structure, and magnetism of a 1D compound engineered from a biradical [5,5'-Bis(3''-oxide-1''-oxyl-4'',4'',5'',5''-tetramethylimidazolin-2''-yl)-2,2'-bipyridine] and Mn(II)(hfac)2

The synthesis, crystal structure, and magnetic properties of a one-dimensional compound, {[Mn(hfac)2]2(biradical)}n (1), resulting from the coordination of bis(hexafluoroacethylacetonato)manganese(II) [Mn(hfac)2] with a biradical obtained by grafting two nitronyl nitroxide radicals in the 5 and 5' positions of a 2,2'-bipyridine ligand are described. Compound 1 crystallizes in the triclinic P space group with the following parameters: a = 11.905(2) A, b = 12.911(2) A, c = 20.163(3) A, alpha = 73.556(3) degrees , beta = 80.850(3) degrees , gamma = 82.126(3) degrees , Z = 2. The bipyridyl moiety acts as a chelate toward one [Mn(hfac)2] unit, while the pendent nitronyl nitroxide radicals are symmetrically bound in trans-configuration to additional [Mn(hfac)2] units. The result is infinite chains running along the c axis direction with the biradical bridging [Mn(hfac)2] units with pending bipyridine/Mn(hfac)2 cores. The magnetic behavior is characteristic of ferrimagnetic chains. Qualitatively we observe first the antiferromagnetic coupling (J2) of each manganese(II) center with two nitronyl nitroxide moieties, leading to a minimum in the chiT product of 6.63 emu K mol(-1) observed at 70 K and corresponding to a ground spin state S = 3/2 plus one extra spin S = 5/2 coming from the pending manganese(II) center. The increase of chiT at lower temperature is understood as a fictive ferromagnetic coupling related to the true antiferromagnetic coupling J1 of the pseudospin S = 3/2 with spin S = 5/2 of the pending manganese(II). Along this approach (H = -JSiSj) the best fit (300-8 K) of the experimental data leads to J1 = -0.622 +/- 0.022 cm(-1) and J2 = -203 +/- 3 cm(-1) with g(Rad) = 2.0017 +/- 0.0015 and g(Mn) = 2.0017 +/- 0.0015.     

Rational synthesis and magnetic properties of a family of low-dimensional heterometallic Cr-Mn complexes based on the versatile building block [Cr(2,2'-bipyridine)(CN)4]-

Six heterometallic compounds based on the building block [Cr(bpy)(CN)4]- (bpy = 2,2'-bipyridine) with secondary and/or tertiary coligands as modulators, {Mn(H2O)2[Cr(bpy)(CN)4]2}n (1), {Mn(bpy)(H2O)[Cr(bpy)(CN)4]2 x H2O}n (2), [Mn(bpy)2][Cr(bpy)(CN)4]2 x 5H2O (3), {[Mn(dca)(bpy)(H2O)][Cr(bpy)(CN)4] x H2O}n (4) (dca = N(CN)2(-)), {Mn(N3)(CH3OH)[Cr(bpy)(CN)4] x 2H2O}n (5), and {Mn(bpy)(N3)(H2O)[Cr(bpy)(CN)4] x H2O}2 (6), have been prepared and characterized structurally and magnetically. X-ray crystallography reveals that the compounds 1, 2, 4, and 5 consist of one-dimensional (1D) chains with different structures: a 4,2-ribbon-like chain, a branched zigzag chain, a 2,2-CC zigzag chain, and a 3,3-ladder-like chain, respectively. It also reveals that compound 3 has a trinuclear [MnCr2] structure, and compound 6 has a tetranuclear [Mn2Cr2] square structure. Magnetic studies show antiferromagnetic interaction between Cr(III) and Mn(II) ions in all compounds. All of the chain compounds exhibit metamagnetic behaviors with different critical temperatures (Tc) and critical fields (Hc; at 1.8 K): 3.2 K and 3.0 kOe for 1; 2.3 K and 4.0 kOe for 2; 2.1 K and 1.0 kOe for 4; and 4.7 K and 5.0 kOe for 5, respectively. The noncentrosymmetric compound 2 is also a weak ferromagnet at low temperature because of spin canting. The magnetic analyses reveal Cr-Mn intermetallic magnetic exchange constants, J, of -4.7 to -9.4 cm(-1) (H = -JS(Cr) x S(Mn)). It is observed that the antiferromagnetic interaction through the Mn-N-C-Cr bridge increases as the Mn-N-C angle (theta) decreases to the range of 155-180 degrees, obeying an empirical relationship: J = -40 + 0.2theta. This result suggests that the best overlap between t(2g) (high-spin Mn(II)) and t(2g) (low-spin Cr(III)) occurs at an angle of approximately 155 degrees.     

Synthesis,crystal structure,and magnetic properties of ([Cu(oxbe)]Mn(H(2)O)[Cu(oxbe)(DMF)])(n).nDMF.nH(2)O: From dissymmetrical mononuclear entities to a 3D heterometallic supramolecular coordination polymer

Self-assembly of the building block [Cu(oxbe)](-) with Mn(II) led to a novel coordination polymer ([Cu(oxbe)]Mn(H(2)O)[Cu(oxbe)(DMF)])n).nDMF.nH(2)O, where H(3)oxbe is a new dissymmetrical ligand N-benzoato-N'-(2-aminoethyl)oxamido and DMF = dimethylformamide. The crystal forms in the triclinic system, space group Ponemacr;, with a = 9.260(4) A, b = 12.833(5) A, c = 15.274(6) A, alpha = 76.18(3) degrees, beta = 82.7(3) degrees, gamma = 82.31(3) degrees, and Z = 2. The crystal structure of the title complex reveals that the two-dimensional bimetallic layers are constructed of Cu(II)Mn(II)Cu(II) chains linked together by carboxylate bridge and hydrogen bonds help to produce a novel three-dimensional channel-like structure. The magnetic susceptibility measurements (5-300 K) were analyzed by means of the Hamiltonian H = -2JS(Mn)(S(Cu1) + S(Cu2)), leading to J = -17.4 cm(-1).     

A new partially deprotonated mixed-valence manganese(II,III) hydroxide-arsenate with electronic conductivity: magnetic properties of high- and room-temperature sarkinite

A new three-dimensional hydroxide-arsenate compound called compound 2 has been synthesized by heating (in air) of the sarkinite phase, Mn(2)(OH)AsO(4) (compound 1), with temperature and time control. The crystal structure of this high-temperature compound has been solved by Patterson-function direct methods. A relevant feature of this new material is that it is actually the first member of the adamite-type family with mixed-valence manganese(II,III) and electronic conductivity. Crystal data: a = 6.7367(5) ?, b = 7.5220(6) ?, c = 9.8117(6) ?, α = 92.410(4)°, β = 109.840(4)°, γ = 115.946(4)°, P1?. The unit cell content derived from Rietveld refinement is Mn(8)(O(4)H(x))(AsO(4))(4). Its framework, projected along [111], is characterized by rings of eight Mn atoms with the OH(-)/O(2-) inside the rings. These rings form an almost perfect hexagonal arrangement with the AsO(4) groups placed in between. Bond-valence analysis indicates both partial deprotonation (x ? 3) and the presence of Mn in two different oxidation states (II and III), which is consistent with the electronic conductivity above 300 °C from electrochemical measurements. The electron paramagnetic resonance spectra of compound 1 and of its high-temperature form compound 2 show the presence of antiferromagnetic interactions with stronger magnetic coupling for the high-temperature phase. Magnetization measurements of room-temperature compound 1 show a complex magnetic behavior, with a three-dimensional antiferromagnetic ordering and magnetic anomalies at low temperatures, whereas for compound 2, an ordered state is not reached. Magnetostructural correlations indicate that superexchange interactions via oxygen are present in both compounds. The values of the magnetic exchange pathways [Mn-O-Mn] are characteristic of antiferromagnetic couplings. Notwithstanding, the existence of competition between different magnetic interactions through superexchange pathways can cause the complex magnetic behavior of compound 1. The loss of three-dimensional magnetic ordering by heating of compound 1 could well be based on the presence of Mn(3+) ions (d(4)) in compound 2.     

Synthetic, X-ray Structure, Electron Paramagnetic Resonance, and Magnetic Studies of the Manganese(II) Complex of 1-Thia-4,7-diazacyclononane ([9]aneN(2)S)

Reaction of manganese(II) perchlorate hexahydrate with a methanol solution of 1-thia-4,7-diazacyclononane ([9]aneN(2)S) resulted in the isolation of the manganese(II) complex [Mn([9]aneN(2)S)(2)](ClO(4))(2). The X-ray structure of this complex is reported: crystal system orthorhombic, space group Pbam, No. 55, a = 7.937(2) ?,b = 8.811(2) ?, c = 15.531(3) ?, Z = 2, R = 0.0579. The complex is high spin (S = (5)/(2)) with an effective magnetic moment (&mgr;(eff)) 5.82 &mgr;(B) at 298 K and 5.65 &mgr;(B) at 4.2 K. Computer simulation of the Q-band EPR spectrum of [Mn([9]aneN(2)S)(2)](ClO(4))(2) yields g = 1.99 +/- 0.01, |D| = 0.19 +/- 0.005 cm(-)(1), and E/D = 0.04 +/- 0.02. For the analogous hexaamine complex [Mn([9]aneN(3))(2)](ClO(4))(2) ([9]aneN(3) = 1,4,7-triazacyclononane) analysis of the EPR spectra produced the following values: g = 1.98 +/- 0.01, |D| = 0.09 +/- 0.003 cm(-)(1), and E/D = 0.1 +/- 0.01. The spin Hamiltonian parameters for [Mn([9]aneN(2)S)(2)](ClO(4))(2) derived from the EPR spectra produced a good fit to the magnetic susceptibility data.     

一个二维梯状化合物[Ni(μ1，5-dca)2(en)]n的合成，结构和磁性(英)

A new nickel(Ⅱ)-dicyanamide compound, [Ni(dca)₂(en)]_n (1) (dca=dicyanamide anion, [N(CN)₂]^-); en=ethylene diamine), has been synthesized and its structure has been determined by single crystal X-ray diffraction analysis. The crystal is monoclinic, space group P2₁/n with unit cell dimensions: a=0.694 3(1) nm, b=1.041 5(2) nm, c=1.4132(2) nm, and β=90.381°, Z=4, V=1.011 0(3) nm³. In this compound, the adjacent nickel atoms are connected by dca all in μ_1，5-bridging mode to form ladder-like units, which are linked with double dca bridges to generate a regular infinite stair-like structure. Temperature-dependent magnetic susceptibility was also characterized for this compound. CCDC: 208276.