Bridging nitrate groups in [Mn(4)O(3)(NO(3))(O(2)CMe)(3)(R(2)dbm)(3)] (R = H, Et) and [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)): acidolysis routes to tetranuclear manganese carboxylate complexes

New synthesis procedures are described to tetranuclear manganese carboxylate complexes containing the [Mn(4)O(2)](8+) or [Mn(4)O(3)X](6+) (X(-) = MeCO(2)(-), F(-), Cl(-), Br(-), NO(3)(-)) core. These involve acidolysis reactions of [Mn(4)O(3)(O(2)CMe)(4)(dbm)(3)] (1; dbm is the anion of dibenzoylmethane) or [Mn(4)O(2)(O(2)CEt)(6)(dbm)(2)] (8) with HX (X(-) = F(-), Cl(-), Br(-), NO(3)(-)); high-yield routes to 1 and 8 are also described. The X(-) = NO(3)(-) complexes [Mn(4)O(3)(NO(3))(O(2)CR)(3)(R'(2)dbm)(3)] (R = Me, R' = H (6); R = Me, R' = Et (7); R = Et, R' = H (12)) represent the first synthesis of the [Mn(4)O(3)(NO(3))](6+) core, which contains an unusual eta(1):mu(3)-NO(3)(-) group. Treatment of known [Mn(4)O(2)(O(2)CEt)(7)(bpy)(2)](ClO(4)) with HNO(3) gives [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)) (15) containing a eta(1):eta(1):mu-NO(3)(-) group bridging the two body Mn(III) ions of the [Mn(4)O(2)](8+) butterfly core. Complex 7 x 4CH(2)Cl(2) crystallizes in space group P2(1)2(1)2(1) with (at -168 degrees C) a = 21.110(3) A, b = 22.183(3) A, c = 15.958(2) A, Z = 4, and V = 7472.4(3) A(3). Complex 15 x (3)/(2)CH(2)Cl(2) crystallizes in space group P2(1)/c with (at -165 degrees C) a = 26.025(4) A, b = 13.488(2) A, c = 32.102(6) A, beta = 97.27(1) degrees, Z = 8, and V = 11178(5) A(3). Complex 7 contains a [Mn(4)(mu(3)-O)(3)(mu(3)-NO(3))](6+) core (3Mn(III), Mn(IV)) as seen for previous [Mn(4)O(3)X](6+) complexes. Complex 15 contains a butterfly [Mn(4)(mu(3)-O)(2)](8+) core. (1)H NMR spectra have been recorded for all complexes reported in this work and the various resonances assigned. All complexes retain their structural integrity on dissolution in chloroform and dichloromethane. Magnetic susceptibility (chi(M)) data were collected on 12 in the 5-300 K range in a 10.0 kG (1 T) field. Fitting of the data to the theoretical chi(M) vs T expression appropriate for a [Mn(4)O(3)X](6+) complex of C(3)(v)() symmetry gave J(34) = -23.9 cm(-)(1), J(33) = 4.9 cm(-)(1), and g = 1.98, where J(34) and J(33) refer to the Mn(III)Mn(IV) and Mn(III)Mn(III) pairwise exchange interactions, respectively. The ground state of the molecule is S = 9/2, as found previously for other [Mn(4)O(3)X](6+) complexes. This was confirmed by magnetization data collected at various fields and temperatures. Fitting of the data gave S = 9/2, D = -0.45 cm(-1), and g = 1.96, where D is the axial zero-field splitting parameter.     

Optical detection of spin polarization in single-molecule magnets [Mn(12)O(12)(O(2)CR)(16)(H(2)O)(4)

A magneto-optical study has been undertaken of the mixed-valence single-molecule magnet [Mn(IV)(4)Mn(III)(8)O(12)L(16)] in which the ligands, L, are acetate (Mn(12)Ac) or the long-chain carboxylic acid, C(14)H(29)COOH (Mn(12)C(15)), that confers better solubility in organic solvents. Thin polymer films of these compounds in poly(methyl methacrylate) (PMM) have been cast by solvent evaporation to provide samples suitable for variable-temperature and field magnetic circular dichroism (MCD) studies. The absorption spectra in isotropic light are featureless, whereas the low-temperature MCD spectra contain resolved peaks, both positive and negative. MCD magnetization curves measured at temperatures above 4.2 K have established a ground-state spin of S = 10 and an axial zero-field parameter, D, of -0.61 K, similar to that determined for single crystals of Mn(12)Ac. By studying at a variety of optical wavelengths, the polarization ratios of the optical transitions relative to the unique axis of the zero-field distortion have been determined. The MCD magnetization curves measured at 4.2 K between 0 and 5 T for the case of Mn(12)C(15) in the PMM film can be fitted only on the assumption of nonrandom distribution of molecular z-axes arising from stresses in the polymer film during the process of casting. MCD-detected hysteresis curves measured in both frozen solution and PMM films, below the blocking temperature of approximately 3 K, show a high retention of spin polarization after reduction to zero of a polarizing magnetic field. This generates intense zero-field circular dichroism (CD) with maximum intensity for xy-polarized optical transitions whose sign depends on the direction of the original polarizing field. The optical polarization and the selection rules for MCD select a subset of molecular orientations with respect to the direction of field. Thus, the magnetically induced CD provides a highly sensitive and rapid optical method of reading the spin polarization of molecular magnets.     

[Mn12O12(O2CMe)12(NO3)4(H2O)4]: facile synthesis of a new type of Mn12 complex

The title dodecanuclear Mn complex, namely dodeca‐μ₂‐acetato‐κ²⁴O:O′‐tetraaquatetra‐μ₂‐nitrato‐κ⁸O:O′‐tetra‐μ₄‐oxido‐octa‐μ₃‐oxido‐tetramanganese(IV)octamanganese(III) nitromethane tetrasolvate, [Mn₁₂(CH₃COO)₁₂(NO₃)₄O₁₂(H₂O)₄]·4CH₃NO₂, was synthesized by the reaction of Mn²⁺ and Ce⁴⁺ sources in nitromethane with an excess of acetic acid. This compound is distinct from the previously known single‐molecule magnet [Mn₁₂O₁₂(O₂CMe)₁₆(H₂O)₄], synthesized by Lis [Acta Cryst. (1980), B 36 , 2042–2044]. It is the first Mn₁₂‐type molecule containing nitrate ligands to be directly synthesized without the use of a preformed cluster. Additionally, this molecule is distinct from all other known Mn₁₂ complexes due to intermolecular hydrogen bonds between the nitrate and water ligands, which give rise to a three‐dimensional network. The complex is compared to other known Mn₁₂ molecules in terms of its structural parameters and symmetry.     

Fe(bipy)(CN)(4)](-) as a versatile building block for the design of heterometallic systems: synthesis, crystal structure, and magnetic properties of PPh(4)[Fe(III)(bipy)(CN)(4)] x H(2)O, [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] x 4H(2)O, and [[Fe(III)(bipy)(CN)(4)](2)Zn(II)] x 2H(2)O [bipy = 2,2'-Bipyridine; M = Mn and Zn

The new cyano complexes of formulas PPh(4)[Fe(III)(bipy)(CN)(4)] x H(2)O (1), [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] x 4H(2)O with M = Mn (2) and Zn (3), and [[Fe(III)(bipy)(CN)(4)](2)Zn(II)] x 2H(2)O (4) [bipy = 2,2'-bipyridine and PPh(4) = tetraphenylphosphonium cation] have been synthesized and structurally characterized. The structure of complex 1 is made up of mononuclear [Fe(bipy)(CN)(4)](-) anions, tetraphenyphosphonium cations, and water molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of a chelating bipy and four carbon atoms of four terminal cyanide groups, building a distorted octahedron around the metal atom. The structure of complexes 2 and 3 consists of neutral centrosymmetric [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] heterotrinuclear units and crystallization water molecules. The [Fe(bipy)(CN)(4)](-) entity of 1 is present in 2 and 3 acting as a monodentate ligand toward M(H(2)O)(4) units [M = Mn(II) (2) and Zn(II) (3)] through one cyanide group, the other three cyanides remaining terminal. Four water molecules and two cyanide nitrogen atoms from two [Fe(bipy)(CN)(4)](-) units in trans positions build a distorted octahedron surrounding Mn(II) (2) and Zn(II) (3). The structure of the [Fe(phen)(CN)(4)](-) complex ligand in 2 and 3 is close to that of the one in 1. The intramolecular Fe-M distances are 5.126(1) and 5.018(1) A in 2 and 3, respectively. 4 exhibits a neutral one-dimensional polymeric structure containing two types of [Fe(bipy)(CN)(4)](-) units acting as bismonodentate (Fe(1)) and trismonodentate (Fe(2)) ligands versus the divalent zinc cations through two cis-cyanide (Fe(1)) and three fac-cyanide (Fe(2)) groups. The environment of the iron atoms in 4 is distorted octahedral as in 1-3, whereas the zinc atom is pentacoordinated with five cyanide nitrogen atoms, describing a very distorted square pyramid. The iron-zinc separations across the single bridging cyanides are 5.013(1) and 5.142(1) A at Fe(1) and 5.028(1), 5.076(1), and 5.176(1) A at Fe(2). The magnetic properties of 1-3 have been investigated in the temperature range 2.0-300 K. 1 is a low-spin iron(III) complex with an important orbital contribution. The magnetic properties of 3 correspond to the sum of two magnetically isolated spin triplets, the antiferromagnetic coupling between the low-spin iron(III) centers through the -CN-Zn-NC- bridging skeleton (iron-iron separation larger than 10 A) being very weak. More interestingly, 2 exhibits a significant intramolecular antiferromagnetic interaction between the central spin sextet and peripheral spin doublets, leading to a low-lying spin quartet.     

Synthesis of RuHCl(CO)(Hdmpz)(L)2 (L=PPh3, AsPh3, and Hdmpz=3,5-dimethylpyrazole) and crystal structure of RuHCl(CO)(Hdmpz)(AsPh3)2

Treatment of RuHCl(CO)(L)₃ with a slight excess amount of K[HB(3,5-Me₂pz)₃] in boiling MeOH solution yielded unusual 3,5-dimethylpyrzaole (Hdmpz) complexes, RuHCl(CO)(Hdmpz)(L)₂ (L=PPh₃, 1 or AsPh₃, 2). Unexpectedly the dissociation of the bonds between the boron atom and the nitrogen atoms of the potentially tridentate [HB(3,5-Me₂pz)₃]⁻ ligand during the coordination of the ligand to the Ru^II metal has been observed. In a separate preparation, the RuHCl(CO)(Hdmpz)(PPh₃)₂ complex has also been synthesized from the reaction between RuHCl(CO)(PPh₃)₃ and the monodentate Hdmpz ligand. Complexes 1 and 2 have been characterized by elemental analysis, IR and ¹H NMR spectroscopies. Compound 1 has also been prepared by the reaction between RuHCl(CO)(PPh₃)₃ and K[H₂B(3,5-Me₂pz)₂] in boiling toluene solution. The crystal structure of 2 has been studied by X-ray crystallography. The geometrical structure around Ru^II of 2 is a distorted octahedral structure. The crystal structure of 2 consists of a discrete monomeric compound. It is interesting to find that the sterically-demanding [HB(3,5-Me₂pz)₃]⁻ or [H₂B(3,5-Me₂pz)₂]⁻ ligands break up during the reaction with the Ru^II complexes to form the neutral 3,5-dimethylpyrazole complexes. In contrast to these observations, [H₂Bpz₂]⁻ and [H₂B(4-Brpz)₂]⁻ ligands form very stable Ru^II complexes.     

Photoinduced magnetization of the cyano-bridged 3d-4f heterobimetallic assembly Nd(DMF)(4)(H(2)O)(3)(micro-CN)Fe(CN)(5).H(2)O (DMF = N,N-dimethylformamide)

Photoinduced magnetization of the cyano-bridged 3d-4f heterobimetallic assembly Nd(DMF)4(H2O)3(mu-CN)Fe(CN)5.H2O (1) (DMF = N,N-dimethylformamide) is described in this paper. The chiMT values are enhanced by about 45% after UV light illumination in the temperature range of 5-50 K. We propose that UV light illumination induces a structural distortion in 1. This small structural change is propagated by molecular interactions in the inorganic network. Furthermore, the cooperativity resulting from the molecular interaction functions to increase the activation energy of the relaxation processes, which makes observation of the photoexcited state possible. The flexible network structure through the hydrogen bonds in 1 plays an essential role for the photoinduced phenomenon. This finding may open up a new domain for developing the molecule-based magnetic materials.     

[Fe(C12H8N3O2)Cl2(ROH)], with R = Me and Et

The title octahedral complexes, [bis(pyridine‐2‐carbonyl)­amin­ate]­di­chloro­(methanol)­iron(III), [Fe(C₁₂H₈N₃O₂)­Cl₂‐(CH₄O)], and [bis­(pyri­dine‐2‐carbonyl)­amin­ate]­di­chloro‐(ethanol)­iron(III), [Fe­(C₁₂H₈N₃O₂)Cl₂(C₂H₆O)], both crystallize in space group and have similar structures. Mono­anionic bpca^? [bis(pyridine‐2‐carbonyl)­amin­ate] acts as a planar tridentate ligand in both cases. Coordination bond distances are in the range typical of high‐spin Fe^III complexes. Carbon–oxygen distances are typical of a C=O double bond suggesting the negative charge of the bpca^? ligand is localized on the central N atom.     

Novel rectangular [Fe4(mu4-OHO)(mu-OH)(2)](7+) versus "butterfly" [Fe4(mu3-O2](8+) core topology in the Fe(III)/RCO2(-)/phen reaction systems (R = Me,Ph; phen = 1,10-phenanthroline): preparation and properties of [Fe4(OHO)(OH)(2)(O2CMe)(4)(phen)(4)](ClO4)(3), [Fe4O2(O2CPh)(7)(phen)(2)](ClO4), and [Fe4O2(O2CPh)(8)(phen)(2)

The preparations, X-ray structures, and detailed physical characterizations are presented for three new tetranuclear Fe(III)/RCO(2)(-)/phen complexes, where phen = 1,10-phenanthroline: [Fe(4)(OHO)(OH)(2)(O(2)CMe)(4)(phen)(4)](ClO(4))(3).4.4MeCN.H(2)O (1.4.4MeCN.H(2)O); [Fe(4)O(2)(O(2)CPh)(7)(phen)(2)](ClO(4)).2MeCN (2.2MeCN); [Fe(4)O(2)(O(2)CPh)(8)(phen)(2)].2H(2)O (3.2H(2)O). Complex 1.4.4MeCN.H(2)O crystallizes in space group P2(1)/n, with a = 18.162(9) A, b = 39.016(19) A, c = 13.054(7) A, beta = 104.29(2) degrees, Z = 4, and V = 8963.7 A(3). Complex 2.2MeCN crystallizes in space group P2(1)/n, with a = 18.532(2) A, b = 35.908(3) A, c = 11.591(1) A, beta = 96.42(1) degrees, Z = 4, and V = 7665(1) A(3). Complex 3.2H(2)O crystallizes in space group I2/a, with a = 18.79(1) A, b = 22.80(1) A, c = 20.74(1) A, beta = 113.21(2) degrees, Z = 4, and V = 8166(1) A(3). The cation of 1 contains the novel [Fe(4)(mu(4)-OHO)(mu-OH)(2)](7+) core. The core structure of 2 and 3 consists of a tetranuclear bis(mu(3)-O) cluster disposed in a "butterfly" arrangement. Magnetic susceptibility data were collected on 1-3 in the 2-300 K range. For the rectangular complex 1, fitting the data to the appropriate theoretical chi(M) vs T expression gave J(1) = -75.4 cm(-1), J(2) = -21.4 cm(-1), and g = 2.0(1), where J(1) and J(2) refer to the Fe(III)O(O(2)CMe)(2)Fe(III) and Fe(III)(OH)Fe(III) pairwise exchange interactions, respectively. The S = 0 ground state of 1 was confirmed by 2 K magnetization data. The data for 2 and 3 reveal a diamagnetic ground state with antiferromagnetic exchange interactions among the four high-spin Fe(III) ions. The exchange coupling constant J(bb) ("body-body" interaction) is indeterminate due to prevailing spin frustration, but the "wing-body" antiferromagnetic interaction (J(wb)) was evaluated to be -77.6 and -65.7 cm(-1) for 2 and 3, respectively, using the appropriate spin Hamiltonian approach. M?ssbauer spectra of 1-3 are consistent with high-spin Fe(III) ions. The data indicated asymmetry of the Fe(4) core of 1 at 80 K, which is not detected at room temperature due to thermal motion of the core. The spectra of 2 and 3 analyze as two quadrupole-split doublets which were assigned to the body and wing-tip pairs of metal ions. (1)H NMR spectra are reported for 1-3 with assignment of the main resonances.     

An Approach to Heterometallic Complexes with Selenolate and Tellurolate Ligands: Crystal Structures of cis-[Mn(CO)(4)(SePh)(2)](-), [(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)](-), (CO)(4)Mn(&mgr;-TePh)(2)Co(CO)(&mgr;-SePh)(3)Mn(CO)(3), and (CO)(3)Mn(&mgr;-SePh)(3)Fe(CO)(3)

Oxidative addition of diorganyl diselenides to the coordinatively unsaturated, low-valent transition-metal-carbonyl fragment [Mn(CO)(5)](-) produced cis-[Mn(CO)(4)(SeR)(2)](-). The complex cis-[PPN][Mn(CO)(4)(SePh)(2)] crystallized in triclinic space group P&onemacr; with a = 10.892(8) ?, b = 10.992(7) ?, c = 27.021(4) ?, alpha = 101.93(4) degrees, beta = 89.79(5) degrees, gamma = 116.94(5) degrees, V = 2807(3) ?(3), and Z = 2; final R = 0.085 and R(w) = 0.094. Thermolytic transformation of cis-[Mn(CO)(4)(SeMe)(2)](-) to [(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)](-) was accomplished in high yield in THF at room temperature. Crystal data for [Na-18-crown-6-ether][(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)]: trigonal space group R&thremacr;, a = 13.533(3) ?, c = 32.292(8) ?, V = 5122(2) ?(3), Z = 6, R = 0.042, R(w) = 0.041. Oxidation of Co(2+) to Co(3+) by diphenyl diselenide in the presence of chelating metallo ligands cis-[Mn(CO)(4)(SePh)(2)](-) and cis-[Mn(CO)(4)(TePh)(2)](-), followed by a bezenselenolate ligand rearranging to bridge two metals and a labile carbonyl shift from Mn to Co, led directly to [(CO)(4)Mn(&mgr;-TePh)(2)Co(CO)(&mgr;-SePh)(3)Mn(CO)(3)]. Crystal data: triclinic space group P&onemacr;, a = 11.712(3) ?, b = 12.197(3) ?, c = 15.754(3) ?, alpha = 83.56(2) degrees, beta = 76.13(2) degrees, gamma = 72.69(2) degrees, V = 2083.8(7) ?(3), Z = 2, R = 0.040, R(w) = 0.040. Addition of fac-[Fe(CO)(3)(SePh)(3)](-) to fac-[Mn(CO)(3)(CH(3)CN)(3)](+) resulted in formation of (CO)(3)Mn(&mgr;-SePh)(3)Fe(CO)(3). This neutral heterometallic complex crystallized in monoclinic space group P2(1)/n with a = 8.707(2) ?, b = 17.413(4) ?, c = 17.541(4) ?, beta = 99.72(2) degrees, V = 2621(1) ?(3), and Z = 4; final R = 0.033 and R(w) = 0.030.     

Single-molecule magnets: a new family of Mn(12) clusters of formula [Mn(12)O(8)X(4)(O(2)CPh)(8)L(6)

The reaction of (NBu(n)(4))[Mn(8)O(6)Cl(6)(O(2)CPh)(7)(H(2)O)(2)] (1) with 2-(hydroxymethyl)pyridine (hmpH) or 2-(hydroxyethyl)pyridine (hepH) gives the Mn(II)(2)Mn(III)(10) title compounds [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hmp)(6)] (2) and [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hep)(6)] (3), respectively, with X = Cl. Subsequent reaction of 3 with HBr affords the Br(-) analogue [Mn(12)O(8)Br(4)(O(2)CPh)(8)(hep)(6)] (4). Complexes 2.2Et(2)O.4CH(2)Cl(2), 3.7CH(2)Cl(2), and 4.2Et(2)O.1.4CH(2)Cl(2) crystallize in the triclinic space group P1, monoclinic space group C2/c, and tetragonal space group I4(1)/a, respectively. Complexes 2 and 3 represent a new structural type, possessing isomeric [Mn(III)(10)Mn(II)(2)O(16)Cl(2)] cores but with differing peripheral ligation. Complex 4 is essentially isostructural with 3. A magnetochemical investigation of complex 2 reveals an S = 6 or 7 ground state and frequency-dependent out-of-phase signals in ac susceptibility studies that establish it as a new class of single-molecule magnet. These signals occur at temperatures higher than those observed for all previously reported single-molecule magnets that are not derived from [Mn(12)O(12)(O(2)CR)(16)(H(2)O)(x)]. A detailed investigation of forms of complex 2 with different solvation levels reveals that the magnetic properties of 2 are extremely sensitive to the latter, emphasizing the importance to the single-molecule magnet properties of interstitial solvent molecules in the samples. In contrast, complexes 3 and 4 are low-spin molecules with an S = 0 ground state.     

Structures of novel R(2)Mo(5)O(18) and R(6)Mo(12)O(45) (R = Eu and Gd) prepared by thermal decomposition of polyoxomolybdate precursor [R2(H2O)(12)Mo(8)O(27)].nH2O

Single crystals of R(2)Mo(5)O(18) and R(6)Mo(12)O(45) (R = Eu and Gd), which are novel compounds in the R(2)O(3)-MoO(3) system, have been obtained by thermal decomposition of [R(2)(H(2)O)(12)Mo(8)O(27)].nH(2)O in air at 750 degrees C for 2 h. TG-DTA and X-ray diffractometry showed that R(2)Mo(5)O(18) crystallizes in a melt of the dehydrated precursor (R(2)Mo(8)O(27)), and R(2)Mo(5)O(18) is transformed to R(6)Mo(12)O(45) in the solid state, both occurring with the loss of MoO(3). R(2)Mo(5)O(18) species crystallize isostructurallyas orthorhombic, Pbcn, Z = 4, with lattice constants of a = 19.2612(7) and 19.246(1) A, b = 9.4618(3) and 9.4414(5) A, c = 9.3779(3) and 9.3446(4) A for R = Eu and Gd, respectively. R(6)Mo(12)O(45) crystallize isostructurally as triclinic P1, Z = 1, with lattice constants of a = 9.3867(4) and 9.3409(3) A, b = 10.9408(5) and 10.8826(5) A, c = 11.4817(5) and 11.4377(5) A, alpha = 104.194(2) degrees and 104.170(1) degrees, beta = 109.567(3) degrees and 109.288(4) degrees, gamma = 108.998(2) degrees and 109.266(2) degrees for R = Eu and Gd, respectively. Both structures consist of [RO(8)] square-antiprisms and [MoO(n)] polyhedra. In R(2)Mo(5)O(18), an [RO(8)] polyhedron is attached by only molybdate groups, being isolated from adjacent [RO(8)] groups. The 12 nearest R atoms surrounding an R atom with R...R distances of 6.0735(4)-7.0389(4) A form an approximate cuboctahedron. All the [RO(8)] square-antiprisms in R(6)Mo(12)O(45) are connected to each other by face-sharing to form dimeric [R(2)O(13)] and [R(2)O(12)] groups. The latter unusual [R(2)O(12)] group is achieved by sharing a square-face via four bridging O atoms with a very short R...R separation (3.4741(7) and 3.4502(6) A for R = Eu and Gd, respectively).     

One- and two-step spin-crossover behavior of [Fe(II)(isoxazole)(6)](2+) and the structure and magnetic properties of triangular [Fe(III)(3)O(OAc)(6)(isoxazole)(3)][ClO(4)

The structure and spin-crossover magnetic behavior of [Fe(II)1(6)][BF(4)](2) (1 = isoxazole) and [Fe(II)1(6)][ClO(4)](2) have been studied. [Fe(II)1(6)][BF(4)](2) undergoes two reversible spin-crossover transitions at 91 and 192 K, and is the first two-step spin transition to undergo a simultaneous crystallographic phase transition, but does not exhibit thermal hysteresis. The single-crystal structure determinations at 260 [space group P3, a = 17.4387(4) A, c = 7.6847(2) A] and at 130 K [space group P1, a = 17.0901(2) A, b = 16.7481(2) A, c = 7.5413(1) A, alpha = 90.5309(6) degrees, beta = 91.5231(6) degrees, gamma = 117.8195(8) degrees ] reveal two different iron sites, Fe1 and Fe2, in a 1:2 ratio. The room-temperature magnetic moment of 5.0 mu(B) is consistent with high-spin Fe(II). A plateau in mu(T) having a moment of 3.3 mu(B) centered at 130 K suggests a mixed spin system of some high-spin and some low-spin Fe(II) molecules. On the basis of the Fe-N bond distances at the two temperatures, and the molar fraction of high-spin molecules at the transition plateau, Fe1 and Fe2 can be assigned to the 91 and 192 K transitions, respectively. [Fe(II)1(6)][ClO(4)](2) [space group P3, a = 17.5829(3) A, c = 7.8043(2) A, beta = 109.820 (3) degrees, T = 295 K] also possesses Fe1:Fe2 in a 1:2 ratio, and magnetic measurements show a single spin transition at 213 K, indicating that both Fe1 and Fe2 undergo a simultaneous spin transition. [Fe(II)1(6)][ClO(4)](2) slowly decomposes in solutions containing acetic anhydride to form [Fe(III)(3)O(OAc)(6)1(3)][ClO(4)] [space group I2, a = 10.1547(7) A, b = 16.5497(11) A, c = 10.3205(9) A, beta = 109.820 (3) degrees, T = 200 K]. The isosceles Fe(3) unit contains two Fe.Fe distances of 3.2844(1) A and a third Fe.Fe distance of 3.2857(1) A. The magnetic data can be fit to a trinuclear model with H = -2J(S(1)xS(2) + S(2)xS(3)) - 2J(13)(S(1)xS(3)), where J = -27.1 and J(13) = -32.5 cm(-1).     

铜配合物[Cu(AFO)2(N3)2](DMF)(H2O)的合成和晶体结构(AFO=4,5-二氮芴-9-酮)

近年来,利用晶体工程方法设计裁剪和组装具有一维、二维、三维框架结构的固体化合物材料已成为材料科学和化学学科中最活跃的研究领域之一。研究表明在这些框架内镶嵌活性组分可得到新型功能材料,如磁性材料、非线性光学材料及新型催化剂等[1]。而叠氮根是一个多功能桥联配体,它能形成一维[2],二维[3],三维[4]等配合物,有关叠氮根的磁性研究也成为分子基铁磁体研究的一个重要方面[5]。本文报道了[Cu(AFO)2(N3)2](DMF)(H2O)(DMF=N,N 二甲基甲酰胺)配合物的合成和晶体结构,并进行了元素分析和红外光谱表征。1　实验部分1 1　试剂与…     

The spin coupling in the diiron complex [Fe2(hpdta)(H2O)3Cl

Density functional, multireference configuration interaction, and modified valence configuration interaction calculations are used to investigate the electronic structure and spin coupling of the dinuclear [Fe(2)(hpdta)(H(2)O)(3)Cl] complex (H(5)hpdta = Hydroxypropane-1,3-diamine-N,N,N',N'-tetraacetic acid). The density functional calculations give evidence of both, states with local high-spin iron centres and states with local low-spin iron centres, the relative energy of which strongly depends on the functional. The splitting of states due to the spin coupling between the high-spin iron centres varies by more than a factor of two for different functionals. In an attempt to study to what extent it is possible to undertake configuration interaction calculations on such binuclear compounds, multireference configuration interaction calculations are performed on a [Fe(2)(OH)(5)(H(2)O)(3)(NH(3))(2)Cl] model complex. The results show that, when correlating only the ten iron 3d orbitals and the four valence orbitals of the bridging OH group, the calculated splitting is still by a factor of about 3 smaller than the value for the splitting inferred from magnetic susceptibility measurements. Modified valence configuration interaction calculations are performed to approximately take into account the influence of orbital relaxation effects of all occupied orbitals in the excited configurations. The exchange splitting is significantly increased, but still smaller than the experimental value.     

四氮杂环十二烷铒配合物的合成及其晶体结构

氮气保护下, 在无水乙腈中合成了1, 4, 7, 10-四氮杂环十二烷(Cyclen)与稀土铒的配合物并得到浅红色棱柱状晶体。元素分析结果表明该配合物的组成为Er(Cyclen)(CF3SO3)3(CH3CN)。用X射线衍射方法研究了其单晶结构。晶体属单斜晶系, P21/a空间群。晶胞参数为a=1.7335(4), b=1.8027(4),c=0.8772(3)nm, β=97.64(3)°, V=2.7171(2)nm^3, Z=4。其中铒为八配位,形成四方反棱柱型配位多面体。     

Synthesis and structure of [Fe(13)O(4)F(24)(OMe)(12)](5-): the first open-shell Keggin ion

The reaction between ferric fluoride trihydrate and pyridine in hot methanol produced yellow-brown crystals of (PyH)5.[Fe13O4F24(OMe)12].4H2O.CH3OH. The anionic complex [Fe13O4F24(OMe)12]5- (1), which has a full Td symmetry, is the first example of an open-shell Keggin ion consisting of 13 high-spin d5 iron(III) atoms. The central, tetrahedral {FeO4} unit in 1 is surrounded by 12 octahedral iron atoms, which are bridged by methoxide oxygen atoms and fluoride ligands. In addition, each of the 12 iron atoms is coordinated to a terminal fluoride ligand with an Fe-F distance of 1.846(3) A. Magnetic susceptibility studies indicate strong exchange interactions between the iron atoms, the mueff value of 19.3 muB at 300 K being significantly lower than that expected for thirteen uncoupled S = 5/2 centers.