Spin crossover transition of Fe(phen)2(NCS)2: periodic dispersion-corrected density-functional study

Periodic dispersion corrected DFT calculations have been performed to study the spin-crossover transition of Fe(phen)(2)(NCS)(2) in the molecular and in the crystalline state. We show that London dispersion interactions play a crucial role in the cohesion of the crystals. Based on calculations of vibrational eigenstates of the isolated molecule and of the crystalline phase in both the low- and high-spin states, the transition entropies and enthalpies have been calculated. We demonstrate that, due to the stabilization of the low-spin state by intermolecular dispersion forces, the transition enthalpy at the transition temperature is larger for the crystalline phase in comparison with an isolated molecule. The effective coordination number of the nitrogen atoms of the ligands around the iron atom has been identified as the order parameter driving the quasi-reversible low-spin to high-spin transition in the crystal. Finally, using constrained geometry relaxations at fixed values of the coordination number, we computed the energy barrier of the LS to HS transition and found it to be in a reasonable agreement with the experimental value.     

氰根桥联三核异金属配合物的合成、晶体结构及磁性研究

采用[(Tp)Fe(CN)₃]-(Tp=hydrotris(pyrazolyl)borate)与Mn(Ac)₂·4H₂O反应，合成了氰根桥联的异金属三核配合物[Mn(phen)₂][(Tp)Fe(CN)₃]₂·5H₂O (1)(phen=1，10-phenanthroline)，并对其结构和磁性进行了研究。晶体结构分析结果表明该化合物晶体属于三斜晶系，P1空间群。在该配合物中，Mn(Ⅱ)与2个phen分子及2个[(Tp)Fe(CN)₃]^-配位，形成一种弯曲的三核结构。磁性测量结果表明，Mn(Ⅱ)和Fe(Ⅲ)之间通过氰根桥联产生弱的反铁磁相互作用。     

[Fe(phen)3]2+ aquation in aqueous polyacrylamide solution

The aquation of tris(1, 10-phenanthroline) iron(II) has been studied in aqueous polyacrylamide solutions. The rate increases up to 2.8 times at low polymer concentrations, and subsequently decreases. These effects are attributed to changes in the local water activity in the region of the complex.

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(1, 10-) (II) . 2,8 , . .

     

Anion effect on the thermolysis of double complexes [Co(NH3)6][Fe(CN)6] and [Co(NH3)6]4[Fe(CN)6]3

The thermolysis of complexes [Co(NH₃)₆][Fe(CN)₆] and [Co(NH_{3 6}]₄[Fe(CN)₆]₃ under an air or hydrogen atmosphere at 200, 350, and 500°C is studied. The composition and properties of thermolysis products are determined. The oxidative thermolysis yields mixtures of oxides of the central metals; the reductive thermolysis yields intermetallic compounds CoFe. The density of the complexes and the specific surface area of the intermetallic compounds are measured. Average particle sizes are calculated. The morphology and dispersion of the powders are dictated by the shape and density of the crystals of the precursor double salts and the thermolysis temperature. The thermolysis chemism in the oxidative and reductive atmospheres is discussed in the context of the nature of the complex anion. Original Russian Text ? S.I. Pechenyuk, D.P. Domonov, D.L. Rogachev, A.T. Belyavskii, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 7, pp. 1110–1115.     

Spin Crossover Properties of the [Fe( PM - BiA )2(NCS)2] Complex – Phases I and II

Summary.  In the present review, we reexamine the photomagnetic properties of the [Fe(PM-BiA)₂(NCS)₂], cis-bis(thiocyanato)-bis[(N-2′-pyridylmethylene)-4-(aminobiphenyl)]iron(II), compound which exhibits, depending on the synthetic method, an exceptionally abrupt spin transition (phase I) with a very narrow hysteresis (T _1/2↓ = 168 K and T _1/2↑ = 173 K) or a gradual spin conversion (phase II) occurring at 190 K. In both cases, light irradiation in the tail of the ¹MLCT-LS absorption band, at 830 nm, results in the population of the high-spin state according to the light-induced excited spin-state trapping (LIESST) effect. The capacity of a compound to retain the light-induced HS information, estimated through the T(LIESST) experiment, is determined for both phases. Interestingly, the shape of the T(LIESST) curve is more gradual for the phase II than for the phase I and the T(LIESST) value is found considerably lower in the case of the phase II. The kinetics parameters involved in the photoinduced high-spin→low-spin relaxation process are estimated for both phases. From these data, the experimental T(LIESST) curves are simulated and the particular influence of the cooperativity as well as of the parameters involved in the thermally activated and tunneling regions are discussed. The Light-Induced Thermal Hysteresis (LITH), originally described for the strongly cooperative phase I, is also reinvestigated. The quasi-static LITH loop is determined by recording the photostationary points in the warming and cooling branches. Corresponding authors. E-mail: letard@icmcb.u-bordeaux.fr Received August 26, 2002; accepted August 30, 2002     

Aggregates of complexes [Sc(H2O)4(NCS)2]+ and [Sc(H2O)2(NCS)4]? with 18-crown-6

The compounds [Sc(H₂O)₄(NCS)₂][Sc(H₂O)₂(NCS)₄] ·2(18C6) (I) and [Sc(H₂O)₄(NCS)₂][Sc(H₂O)₂(NCS)₄] · 3(18C6) · H₂O (II) were synthesized and studied by X-ray diffraction analysis. It was found that the cations in the structures of compounds I and II form sandwiches [Sc(H₂O)₄(NCS)₂] · 2(18C6). In the case of I, the sandwiches are united by the [Sc(H₂O)₂(NCS)₄]⁻ anions into chains, while in compound II, the sandwiches and infinite chains of [Sc(H₂O)₂(NCS)₄] · 18C6 · H₂O are bonded by van der Waals contacts only. Original Russian Text ? A.B. Ilyukhin, S.P. Petrosyants, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 4, pp. 275–281.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

[COH(NH2)2]2[Cu(pic)2(ClO4)2]的合成与晶体结构

The title compound was synthesized by reaction of Cu(ClO₄)₂， picolinic acid and carbamide in C₂H₅OH/CH₃CN solution， and characterized by single-crystal X-ray diffraction. It crystallizes in the orthorhombic system， space group Pbca with a=14.0481(8)， b=9.0130(5)， c=18.626(1)?， V=2358.3(2)?³， Z=4， D_x=1.771g·cm^-3， μ=1.235mm^-1 and F(000)=1276. The final R factor is 0.0440 for 1434 observed reflections. The X-ray analysis revealed that the copper(Ⅱ) atom is coordinated by two picolinic ligands in the equatorial plane， while the two oxygen atoms of perchlorate occupy the axial positions of octahedron with lengthened Cu-O distances， resulting in a 4+2 elongated octahedral environment. In the compound， there also exist two protonated carbamide cations for charge balance. CCDC： 195354.     

Structure and properties of double complex salts [Co(NH3)6][Fe(CN)6] and [Co(NH3)6]2[Cu(C2O4)2]3

Double complex salts (DCSs) [Co(NH₃)₆][Fe(CN)₆] (I) and [Co(NH₃)₆]₂[Cu(C₂O₄)₂]₃ (II) and complex [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O (III) are synthesized and investigated by single crystal XRD, crystal optics, and elemental analysis. The crystalline phases of I, II, and III (R-3, P2₁/c, and Pnnm space groups respectively) have the following crystallographic characteristics: a = 10.9804(2) ?, b = 10.9804(2) ?, c = 10.8224(3) ?, V = 1130.03(4) ?³, Z = 3, d _x = 1.65 g/cm³ (I); a = 9.6370(2) ?, b = 10.2452(2) ?, c = 13.2108(3) ?, V = 1932.90(9) ?³, Z = 2, d _x= 1.97 g/cm³ (II), and a = 11.7658(3) ?, b = 11.7254(3) ?, c = 14.1913(4) ?, V = 1304.34(5) ?³, Z = 2, d _x = 1.68 g/cm³ (III). This paper investigates the products of DCS thermolysis in a hydrogen atmosphere: the intermetallic compound CoFe with the bcc parameter a = 2.852 ? for I and a heterogeneous mixture of Co and Cu in the decomposition of II. The coordinated CN⁻ and C₂O₄²⁻ groups then turn into NH₃, hydrocarbons, and CO₂. The dominant hydrocarbon is methane.     

The synthesis and crystal structure of vanadium complexes: [VO2(phen)2]·6H2O and [2,2′-(bipy)2VO2](H2BO3)·3H2O

The organic-inorganic hybrid materials vanadium oxide [V^IVO₂(phen)₂]·6H₂O (1) and [(2,2′-bipy)₂V^VO₂](H₂BO₃)·3H₂O (2) have been conventional and hydrothermal synthesized and characterized by single crystal X-ray diffraction, elemental analyses, respectively. Although the method and the ligand had been used in the syntheses of the compounds (1) and (2) are different, they almost possess similar structure. They all exhibit the distorted octahedral [VO₂N₄] unit with organonitrogen donors of the phen and 2,2′-bipy ligands, respectively, which coordinated directly to the vanadium oxide framework. And they are both non-mixed-valence complexes. But the compound (1) is isolated, and the compound (2) consists of a cation of [(2,2′-bipy)₂V^VO₂]⁺ and an anion of (H₂BO₃)⁻. So the valence of vanadium of (1) and (2) are tetravalence and pentavalence, respectively. Meanwhile it is noteworthy that π-π stacking interaction between adjacent phen and 2,2′-bipy groups in compounds 1 and 2 also play a significant role in stabilization of the structure. Thus, the structure of [V^IVO₂(phen)₂]·6H₂O and [(2,2′-bipy)₂V^VO₂](H₂BO₃)·3H₂O are both further extended into interesting three-dimensional supramolecular. Crystal data: (1) Triclinic, a=8.481(4), b=12.097(5), and α=66.32(2), β=82.97(3), and γ=82.59(4)°, Z=2, R₁=0.0685, wR₂=0.1522. (2) Triclinic, a=6.643(13), b=11.794(2), and α=101.39(3), β=101.59(3), and γ=97.15(3)°, Z=2, R₁=0.0736, wR₂=0.1998.     

Hydrothermal syntheses and crystal structures of bimetallic cluster complexes [{Cd(phen)2}2V4O12]·5H2O and [Ni(phen)3]2[V4O12]·17.5H2O

The hydrothermal reactions of vanadium oxide starting materials with divalent transition metal cations in the presence of nitrogen donor chelating ligands yield the bimetallic cluster complexes with the formulae [{Cd(phen₂)₂V₄O₁₂]·5H₂O (1) and [Ni(phen)₃]₂[V₄O₁₂]·17.5H₂O (2). Crystal data: C₄₈H₅₂Cd₂N₈O₂₂V₄ (1), triclinic. a=10.3366(10), b=11.320(3), c=13.268(3) Å, =103.888(17)°, β=92.256(15)°, γ=107.444(14)°, Z=1; C₇₂H₁₃₁N₁₂Ni₂O_29.5V₄ (2), triclinic. a=12.305(3), b=13.172(6), c=15.133(4), =79.05(3)°, β=76.09(2)°, γ=74.66(3)°, Z=1. Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range 1.59° <θ<26.02° and 2.01°<θ<25.01° using the ω-scan technique, respectively. The structure of 1 consists of a [V₄O₁₂]⁴⁻ cluster covalently attached to two {Cd(phen)₂}²⁺ fragments, in which the [V₄O₁₂]⁴⁻ cluster adopts a chair-like configuration. In the structure of 2, the [V₄O₁₂]⁴⁻ cluster is isolated. And the complex formed a layer structure via hydrogen bonds between the [V₄O₁₂]⁴⁻ unit and crystallization water molecules.     

Vibrational spectra of the peroxotantalates (NH4)3[Ta(O2)4], K3[Ta(O2)4], Rb3[Ta(O2)4] and Cs3[Ta(O2)4] and the crystal structure of Rb3[Ta(O2)4]

The compounds (NH₄)₃[Ta(O₂)₄], K₃[Ta(O₂)₄], Rb₃[Ta(O₂)₄] and Cs₃[Ta(O₂)₄] have been prepared and investigated by X-ray powder methods as well as Raman- and IR-spectroscopy. In the case of Rb₃[Ta(O₂)₄] the structure has been solved from single crystal data. It is shown that all these compounds are isotypic and crystallize in the K₃[Cr(O₂)₄] type (SG , No. 121). The infrared- and Raman spectra (recorded on powdered samples) are discussed with respect to the internal vibrations of the peroxo-group and the dodecahedral [Ta(O₂)₄]³⁻ ion. Symmetry coordinates for the [Ta(O₂)₄]³⁻ ion are given from which the vibrational modes of the O-O stretching vibrations of the O₂²⁻ groups, the Ta-O stretching vibrations and the Ta-O bending vibrations are deduced.     

Synthesis and X-ray crystallographic structures of [HGa(NMe2)2]2 and [PhGa(NHNMe2)2]2, and room-temperature conversions of [HGa(NMe2)2]2 to (HGaNH)n and (HGaNMe)n

The reactivity of bis(dimethylamido) complexes of phenyl- and hydridogallium with ammonia, dimethylamine and 1,1-dimethylhydrazine is described. Synthesis of the starting gallium hydride, [HGa(NMe₂)₂]₂, was achieved in nearly quantitative yield from the reaction of HGaCl₂(quinuclidine) with LiNMe₂. In neat ammonia or methylamine at room temperature both dimethylamido ligands in [HGa(NMe₂)₂]₂ were substituted by a single equivalent of NH₃ or MeNH₂ to produce amorphous (HGaNH)_n or (HGaNMe)_n, respectively. In contrast, the reaction of [PhGa(NMe₂)₂]₂ with neat Me₂NNH₂, at room temperature consumed two equivalents of the substituted hydrazine to form [PhGa(NHNMe₂)₂]₂ in a 73% yield. Single crystal X-ray crystallographic analyses of [HGa(NMe₂)₂]₂ and [PhGa(NHNMe₂)₂]₂ establish that in the solid state both compounds adopt a cyclic Ga-N-Ga-N structure with a crystallographic center of symmetry located at the center of the ring.     

配合物[Mn(bipy)3](ClO4)2的晶体结构和热分析研究

The complex [Mn(bipy)₃]·(ClO₄)₂ was synthesied and characterized by X-ray diffraction. X-ray diffraction result for the single crystal showed that the crystal belongs to triclinic, space group P1, a=0.8123(2),b=1.1024(2), c=1.8646(4)nm,α=102.30(3)°,β=91.00(3)°,γ=99.69(3)°,V=1.6056(6)nm³,Z=2,D_c=1.494g·cm^-3. The thermal decomposition of [Mn(bipy)₃](ClO₄)₂ occurred in a three steps pattern. The reaction mechanism of the first step decomposition was deduced as n(1-α)[-ln(1-α)](n-1)/n with the activation energy of 130kJ·mol^-1.     

Crystal structure and single crystal EPR of (NH4)2(15-crown-5)3[Cu(mnt)2] and (NH4)2(benzo-15-crown-5)4[Cu(mnt)2]·0.5H2O

The X-ray crystal structures of (NH4)2(15-crown-5)3[Cu(mnt)2] (1) and (NH4)2(benzo-15-crown-5)4- [Cu(mnt)2]·0.5H2O (2) were determined. Two single crystals are composed of distinct structures of ammonium-crown ether supramolecular cation and [Cu(mnt)2]2- anion. The triple-decker dication in complex 1 and a sandwich dimmer in complex 2 were observed. X-Band EPR studies on the single crystals of both complex 1 and complex 2 have been carried out at room temperature, which revealed that complex 2 showed a perfect hyperfine structure of Cu whereas that of complex 1 could not be observed. The principal values and direction cosines of the principal axes of the g and A tensors were computed by a least-squares fitting procedure. The spin density of Cu(Ⅱ) was estimated according to the principal values of the A tensors and compared well with the results calculated based on DFT method.     

新配合物[Cd(H2O)2(phen)2](PA)2的制备及晶体结构

The new compound was prepared by the reaction of Cd(ClO₄)₂·6H₂O,1,10-phenanthroline (phen)and picric acid (HPA)(ratio 1∶3∶2) in methanol-aqueous solution refluxing for 4 hours. The crystals used for X-ray analysis was obtained by slow evaporation of the solution at room temperature. The crystal compound is in triclinic with space group with a=1.1363(4)nm,b=1.2593(2)nm,c=1.3972(4)nm,α=93.97(2)?,β=100.84(3)?,γ=106.29(2)?,Z=2,V=1.8690(9)nm³,D_c=1.715g·cm^-3, μ(MoKα)=0.677mm^-1,F(000)=972,R=0.0907,wR=0.2240. In the complex, the Cd(Ⅱ) cation is octahedrally coordinated to two 1,10-phenanthroline ligands and two water molecules in cis disposition. As outer sphere, picrate anions are combined with inner by hydrogen bond and static electricity interaction.     

Supramolecular 2D structures in [M(NCS)2(bpe)2(H2O)2] (M = Mn, Fe) systems connected by hydrogen bonds

Here we report the synthesis and characterization by X-ray diffraction, FTIR, UV-Vis and EPR spectroscopies, and the magnetic measurements of two new compounds: [Mn(NCS)₂(bpe)₂(H₂O)₂] (1) and [Fe(NCS)₂(bpe)₂(H₂O)₂] (2) (bpe = 1,2-bis(4-pyridyl)ethylene). Single-crystal structure analyses reveals discrete octahedral metal units that are assembled into 2D sheets through O-Hw?N(bpe) and O-Hw?S(thiocyanate) hydrogen bonds. The intermetallic M?M distances are 6.90 and 6.87 Å for 1 and 2, respectively. Supramolecular architectures are obtained by connections through H-bonds. Slight interactions are observed for compound 2.     

配合物[La(pic)3(phen)2]·CH3CN的合成及晶体结构

The Lanthanum picrate complex with 1,10-phenanthroline was synthesized, whose chemical formula can be written in [La(pic)₃(phen)₂]·CH₃CN. The crystal Xray diffraction analysis shows that crystal belongs to monoclinic with space group P2₁/a and unit cell parameters:a=17.072(4),b=16.083(4),c=17.789(4),β=106.34(2)°,V=4687(4)³, Z=4,Dc=1.735g·cm³, μ=10.106cm¹,F(000)=2448,R=0.0589,Rw=0.0589. The coordination number of La³⁺ is nine. Acetonitrile, a solvent molecule is not coordinated. Between three Pic ligands, that possesses 2 bidentate forms six member ring with La. The other is unidentate ligand. As usually, phen is bidentate ligand.