Low-spin→high-spin relaxation dynamics in the highly diluted spin-crossover system [Fe(x)Zn(1-x)(bbtr)3](ClO4)2

Whereas the neat polymeric iron(II) compound [Fe(bbtr)(3)](ClO(4))(2), bbtr = 1,4-di(1,2,3-triazol-1-yl)butane, shows a quantitative spin transition triggered by a crystallographic phase transition centered at 107 K with a 13 K wide hysteresis, the iron(II) complexes in the diluted mixed crystals [Fe(x)Zn(1-x)(bbtr)(3)](ClO(4))(2), x = 0.02 and 0.1, stay predominantly in the (5)T(2) high-spin state down to cryogenic temperatures. However, the (1)A(1) low-spin state can be populated as metastable state via irradiation into the spin-allowed (5)T(2)→(5)E ligand-field transition of the high-spin species in the near-infrared. The quantum efficiency of the light-induced conversion is approximately 10% at low temperatures and decreases rapidly above 160 K. The lifetime of the light-induced low-spin state decreases from 15 days at 40 K to 30 ns at 220 K, that is, by 14 orders of magnitude. In the high-temperature regime the activation energy for the low-spin→high-spin relaxation is 1840(20) cm(-1).     

Thermal and Light-Induced Spin Switching Dynamics in the 2D Coordination Network of {[Zn(1-x)Fe(x)(bbtr)(3)](ClO(4))(2)}(∞): The Role of Cooperative Effects

The thermal spin transition, the photoexcitation, and the subsequent spin relaxation in the mixed crystal series of the covalently linked two-dimensional network {[Zn(1-x)Fe(x)(bbtr)(3)](ClO(4))(2)}(∞) (x = 0.02-1, bbtr =1,4-di(1,2,3-triazol-1-yl)-butane) are discussed. In the neat compound, the thermal spin transition with a hysteresis of 13 K is accompanied by a crystallographic phase transition (Kusz, J.; Bronisz, R.; Zubko, M.; Bednarek, H. Chem. Eur. J.2011, 17, 6807). In contrast, the diluted crystals with x ≤ 0.1 stay essentially in the high-spin state down to low temperatures and show typical first order relaxation kinetics upon photoexcitation, and the structural phase transition is well separated from the spin transition. With increasing Fe(II) concentration, steeper thermal transitions and sigmoidal relaxation curves indicate increasingly important cooperative effects. Already at x = 0.38, the spin relaxation is governed by cooperative interactions between Fe(II) centers, and the crystallographic phase transition begins to influence the spin transition. The kinetic behavior of the thermal spin transition is reproduced within the framework of a dynamic mean-field model.     

Reversibility of light-induced excited spin state trapping in the Fe(ptz)6(BF4)2, and the Zn1−xFex(ptz)6(BF4)2 spin-crossover systems

Fe(ptz)₆(BF₄)₂ (ptz = 1-propyltetrazole) is an iron(II) spin-crossover system which shows light-induced excited spin state trapping. In this paper we show that (a) the same phenomenon can also be observed in Zn_1−xFe_x(ptz)₆(BF₄)₂ (x ≈ 0.1) and is therefore basically a single-ion property, and (b) that the phenomenon is reversible. The efficiency of the light-induced spin crossover is of the order of 0.5% in the forward direction and 0.1% in the reverse direction.     

Synthesis and characterisation of [Ag2Pt4(μ-S)4(PPh3)8](BF4)2 · 0.25CHCl3

[Pt₂(μ₂-S)₂(PPh₃)₄] functions effectively as a bridging bidentate ligand towards Ag⁺ to form [Ag₂Pt₄(μ₃-S)₄(PPh₃)₈]²⁺. A single crystal X-ray crystallographic anaylsis of the BF₄⁻ salt has demonstrated that both Ag⁺ ions are linearly coordinated to the sulphur atoms, but the small bite angle of the [Pt₂(μ-S)₂(PPh₃)₄] ligand leads to an Ag…Ag contact distance of only 2.815(4) Å.     

Photoconduction in [Fe(Htrz)2(trz)](BF4)·H2O nanocrystals

Sub-micron-sized [Fe(Htrz)(2)(trz)](BF(4))·H(2)O nanoparticles that exhibit a spin crossover transition are positioned between Au electrodes with sub-100 nm separation. After voltage poling, samples exhibit unexpected large conductivity, with photoconductance and photovoltaic behavior.     

Synthesis and crystal structure of a novel tartrate copper(II) two-dimensional coordination polymer: {[Cu2(C4H4O6)2(H2O)2]·4H2O}∞

A new 2D coordination polymer, {[Cu₂(C₄H₄O₆)₂(H₂O)₂]·4H₂O}_∞ has been synthesized by the hydrothermal method and characterized by X-ray single crystal diffraction. Every copper(II) atom adopts a distorted octahedral geometry and coordinates with six oxygen atoms from one water molecule and three tartrate acid ions. The two tartrate acid ions have different coordination modes, one provides four oxygen atoms to coordinate with Cu(II) and another coordinates with all six oxygen atoms. Such a coordination mode generates a two-dimensional coordination polymer. In the solid state, the title compound forms a 3D network structure through hydrogen bonds.     

Fe(III) extraction equilibria in the system: Fe2(SO4)3(NH4)2SO4 vs primene JM-T sulfate-toluene

Distribution coefficients for Fe(III) have been determined in the liquid-liquid extraction system Primene JM-T-toluene vs aqueous ammonium sulfate (and sodium sulfate) as a function of sulfate, acid, Fe(III) and amine sulfate concentrations. A study of loading equilibria as a function of time for this system indicates that equilibrium was largely achieved in 1 hr although some changes, possibly in the nature of the extracted species, occur up to approx. 20 hr. Extraction isotherms show a slope of 1 at low loadings, indicating the same degree of self association in both organic and aqueous phases, while the amine sulfate/iron ratio appears to approach 2.5 ± 0.25 at saturation loading. Results obtained by varying the sulfate concentration matrix indicates the formation of an aqueous complex of ferric ammonium sulfate which depresses iron distribution to the organic phase. The degree of aggregation of the amine sulfate, derived from iron distribution coefficient dependence on amine sulfate concentration data, is shown to be approx. 10.     

Energetic materials composed of coordination polymers: {[Zn(μ-atrz)3](ClO4)2·2H2O}n and {[Cu(μ-atrz)3](NO3)2·2H2O}n

An improved synthetic pathway for trans-4,4′-azo-1,2,4-triazole (atrz) was discovered. Pure atrz was obtained directly without any other separation step in an environment friendly process. Treatment of atrz with zinc perchlorate and cupric nitrate led to the isolation of {[Zn(μ-atrz)₃](ClO₄)₂·2H₂O}_n and {[Cu(μ-atrz)₃](NO₃)₂·2H₂O}_n, which were well characterized. Their structures were determined by X-ray crystallographic analysis. The calculation results of the formation of {[Zn(μ-atrz)₃](ClO₄)₂ 2H₂O}_n and {[Cu(μ-atrz)₃](NO₃)₂ 2H₂O}_n indicates that the perfect crystal structures in spite of much resistance. A fundamental understanding of the structure and thermal properties involves factors, such as conjugated system, crystal structure, and inorganic metallic compounds that affect their thermal behavior. The high energy of the coordination compounds consists of chemical, electronic, and potential energy. The potential for the improvement of the coordination polymer opens up a new world for research of energetic materials.     

一种新的具有滞后现象的自旋转换配合物[Fe(PhCH=Ntrz)3](BF4)2·3H2O

自旋转换配合物(又称自旋交叉配合物)由于可用作分子基电子器件材料而受到科学家的广泛关注[1～4].近年来,虽然发现了一些具有自旋交叉现象的Fe(Ⅱ)配合物,但其转换温度多在液氮温度以下且无滞后现象,不能满足实用信息存储材料的要求.     

双金属层状配位聚合物{[ML][FeⅡFeⅡ(Ox)3]·H2O}∞的合成和波谱表征

合成和表征了两种新的Schiff碱配合物[ZnL(ClO4)@4H2O(A)和CdL(ClO4)@3H2O(B)],其中L=2-{[2-(Aminomethyl-amino)-ethylimino]-methyl}-phenol.A(或B)、FeSO4@7H2O和K3[Fe(ox)3]@3H2O进一步反应,生成了配位聚合物{[ML][FeⅡFeⅢ(ox)3]@H2O}∞,其中M=Zn2+(C)或Cd2+(D).红外光谱和Mossbauer谱测定结果表明,C和D具有二维层状结构,其阴离子层由[FeⅡFeⅢ(ox)3]-单元构成.     

Cooperative spin transition in the two-dimensional coordination polymer [Fe(4,4'-bipyridine)2(NCX)2]·4CHCl3 (X = S, Se)

Two new isostructural two-dimensional (2D) coordination polymers exhibiting spin crossover (SCO) behavior of formulation [Fe(4,4'-bipy)(2)(NCX)(2)]·4CHCl(3) (4,4'-bipy = 4,4'-bipyridine; X = S [1·4CHCl(3)], Se [2·4CHCl(3)]) have been synthesized and characterized, and both undergo cooperative spin transitions (ST). For 1·4CHCl(3) the ST takes place in two steps with critical temperatures of T(c1)(down) = 143.1 K, T(c2)(down) = 91.2 K, T(c1)(up) = 150.7 K, and T(c2)(up) = 112.2 K. 2·4CHCl(3) displays half ST characterized by T(c)(down) = 161.7 K and T(c)(up) = 168.3 K. The average enthalpy and entropy variations and cooperativity parameters associated with the ST have been estimated to be ΔH(1)(av) = 5.18 kJ mol(-1), ΔS(1)(av) = 35 J K(-1) mol(-1), and Γ(1) = 2.8 kJ mol(-1) and ΔH(2)(av) = 3.55 kJ mol(-1), ΔS(2)(av) = 35 J K(-1) mol(-1), and Γ(2) = 2.6 kJ mol(-1) for 1·4CHCl(3), and ΔH(av) = 6.25 kJ mol(-1), ΔS(av) = 38.1 J K(-1) mol(-1), and Γ = 3.2 kJ mol(-1) for 2·4CHCl(3). At T > [T(c1) (1·4CHCl(3)); T(c) (2·4CHCl(3))], both compounds are in the space group P2/c while at T < [T(c1) (1·4CHCl(3)); T(c) (2·4CHCl(3))] they change to the C2/c space group and display an ordered checkerboard-like arrangement of iron(II) sites where the high- and low-spin states coexist at 50%.     

Unprecedented lanthanide-containing coordination polymers constructed from hexanuclear molecular building blocks: {[Ln6O(OH)8](NO3)2(bdc)(Hbdc)2·2NO3·H)bdc}∞

Reactions in acetonitrile between 1,4-benzene-dicarboxylic acid (C(8)H(6)O(4)) and a hexanuclear complex of lanthanide [Ln(6)O(OH)(8)(NO(3))(6)·2NO(3)] with Ln = Y or Tb lead to 1D-coordination polymers with the general chemical formula {[Ln(6)O(OH)(8)](NO(3))(2)(bdc)(Hbdc)(2)·2NO(3)·H(2)bdc}(∞) where H(2)bdc stands for 1,4-benzene-dicarboxylic acid (or terephthalic acid). These two compounds are isostructural. The crystal structure has been solved on the basis of the X-ray powder diffraction diagram of the Y-containing compound. This compound crystallizes in the triclinic system, space group P1 (no. 2) with a = 10.4956(6) ?, b = 11.529(2) ?, c = 12.357(2) ?, α = 86.869(9)°, β = 114.272(6)°, γ = 71.624(7)°, V = 1264.02 ?(3), and Z = 2. The crystal structure can be described as the juxtaposition of linear chains of hexanuclear entities linked to each other by terephthalate ligands. Two additional partially protonated terephthalate ligands spreading laterally to the chain are bound to each hexanuclear entity. Another diprotonated terephthalic ligand and two nitrate ions ensuring the electroneutrality of the crystal structure lie in the interchain space. These two compounds are thermally stable until 200 °C. Thanks to a so-called antenna effect, the Tb-containing compound, despite short intermetallic distances, exhibits a strong luminescence under UV irradiation.     

A one-dimensional zigzag coordination polymer: {[Ag(2-amino-3-methylpyridine)](ClO4)}∞

The reaction of silver perchlorate with 2-amino-3-methylpyridine gives a one-dimensional zigzag coordination polymer {[Ag(2-amino-3-methylpyridine)](ClO₄)}_∞ (1) consisting of single chains. The geometry of all Ag(I) cations is linear: each ion links together two 2-pyridyl (Ag1) rings and two 2-amino (Ag2) groups, with the ligand exhibiting a ‘head-to-head’ orientation. Crystal data: monoclinic P2(1)/c, a?=?5.2296(8), b?=?20.668(3), c?=?8.8716(14)?Å, β?=?100.359(3)°, V?=?943.3(3)?ų, Z?=?2, D _c ?=?2.214?Mg/m³, μ?=?2.409?mm^?1, F(000)?=?612, R1?=?0.0426, wR1?=?0.0980 [I?>?2σ(I)], S?=?0.969.     

MOLECULAR RECOGNITION OF AN ORGANIC MOLECULE BY BIS(TETRAFLUOROBORATE)ZINC(II). SYNTHESIS AND CRYSTAL STRUCTURE OF {[Zn(phen)3](BF4)2}2·MNA·(H2O)1.5

Abstract

The 2:1 adduct {[Zn(phen)₃](BF₄)₂}₂·MNA·(H₂O)_1.5 (1) (where phen = 1,10-phenanthroline and MNA = 2-methyl-4-nitrobenzenamine) was prepared by self-assembly and characterized by X-ray crystallography. The central zinc atom in two non-equivalent [Zn(phen)₃]²⁺ cations exhibits distorted octahedral geometry with Zn-N bond distances of 2.151(6)-2.194(6) Å and 2.136(6)-2.210(6) Å, respectively. The 2-methyl-4-nitrobenzenamine molecule is connected with bis(tetrafluoroborate)tris(1,10-phenanthroline)zinc(II) through a hydrogen bond (N13-H13a…F23? 3.044 Å, ?1 - x, 1 - y, - z). High shape specificity was observed in the recognition process.     

SYNTHESIS OF A DINUCLEAR YLID COMPLEX DERIVED FROM P(OPh)3: CRYSTAL STRUCTURES OF [Cp2Fe2(CO)2(μ-CO) (μ-CHP(OPh)3)+][BF4 −] AND [Cp2Fe2(CO)2 (μ-CO)(μ-CHPPh3)+][BF4 −]

Abstract

[Cp₂Fe₂(CO)₂(μ-CO)(μ-CHP(OPh)₃)⁺][BF^? ₄] crystallizes in the centrosymmetric monoclinic space group P2₁/n with a = 12.553(7) Å, b = 16.572(11) Å, c = 15.112(8) Å, β = 100.00(4)°, V = 3096(3) ų and D(calcd.) = 1.579 g/cm³ for Z = 4. The structure was refined to R(F) = 5.83% for 1972 reflections above 4σ(F). The cation contains two CpFe(CO) fragments linked via an iron—iron bond (Fe(1)—Fe(2) = 2.544(3)Å), a bridging carbonyl ligand (Fe(1)—C(4) = 1.918(1) Å, Fe(2)—C(4) = 1.946(12)Å) and a bridging CHP(OPh)₃ ligand (Fe(1)—C(1) = 1.980(9)Å, Fe(2)—C(1) = 1.989(8)Å). Distances within the μ-CHP(OPh)₃ moiety include a rather short carbon—phosphorus bond [C(1)—P(1) = 1.680(10)Å] and P—O bond lengths of 1.550(7)–1.579(6)Å. The crystal is stabilized by a network of F…H—C interactions involving the BF^? ₄ anion.

[Cp₂Fe₂(CO)₂(μ-CO)(μ-CHPPh₃)⁺][BF^? ₄], which differs from the previous compound only in having a μ-CHPPh₃ (rather than μ-CHP(OPh)₃) ligand, crystallizes in the centrosymmetric monoclinic space group P2₁/c with a = 11.248(5)Å, b = 13.855(5)Å, c = 18.920(7)Å, β = 96.25(3)°, V = 2931(2)ų and D(calcd.) = 1.559 g/cm³ for Z = 4. This structure was refined to R(F) = 4.66% for 1985 reflections above 4σ(F). Bond lengths within the dinuclear cation here include Fe(1)-Fe(2) = 2.529(2)Å, Fe(1)—C(3) = 1.904(9) Å and Fe(2)—C(3) = 1.911(8) Å (for the bridging CO ligand) and Fe(1)—C(1P) = 1.995(6) Å and Fe(2)—C(1P) = 1.981(7) Å (for the bridging CHPPh₃ ligand). Distances within the μ-CHPPh₃ ligand include a longer carbon—phosphorus bond [C(1P)—P(1) = 1.768(6)Å] and P(1)—C(phenyl) = 1.797(7)–1.815(8) Å.     

The Structure of Pd2(CH≡CC6H5)2(C5H7O2)3(BF3)2BF4

IR and NMR data showed that the ionic complex Pd₂(CHCC₆H₅)₂(C₅H₇O₂)₃(BF₃)₂BF₄ isolated in the reaction Pd(Acac)₂ + PA + 5BF₃OEt₂ (Acac is C₅H₇O₂, PA is phenylacetylene) is an adduct of two complexes, namely, (Acac)PdBF₄ and [(PA)₂Pd(C³-Acac · BF₃)]⁺(Acac · BF₃)^– (coordinatively unsaturated). On dissolution in deuteroacetone or deuteromethanol, the [(Acac)PdF₂BF₂Pd(C³-Acac · BF₃)(PA)₂]⁺(Acac · BF₃)^– adduct decomposed to Pd(Acac)₂, 2BF₃ · L (L = (CD₃)₂CO, CD₃OD) and the [L(PA)₂Pd(C³-Acac]⁺BF₄ ^– complex.     

Molecular vibration spectroscopy studies on novel trinuclear rhodium-7-hydride complexes of the general type {[Rh(PP*)X]3(μ(2-X)3(μ3-X)}(BF4)2 (X = H, D)

Novel trinuclear rhodium-hydride complexes with diphosphine ligands Tangphos, t-Bu-BisP*, and Me-DuPHOS which contain bridging μ(2)- and μ(3)-hydrides as well as terminal hydrides in one molecule have been reported recently. In this work, these different rhodium-hydride bonds are characterized by Raman spectroscopy and the results are compared with those obtained by means of the more commonly applied IR spectroscopy. Density functional theory (DFT) calculations have been carried out to support the experimental findings. The structure of the Rh(3)H(7) core is described in the context of their vibrational stretching modes.     

The synthesis of the [Fe(Phen)3](iso-Bu2PS2)2 Complex. The crystal structures of [Fe(Phen)3](iso-Bu2PS2)2 · 5H2O and disulfan {iso-Bu2P(S)S}2

The complex [Fe(Phen)₃][iso-Bu₂PS₂)₂ (I) was synthesized and the single crystals of [Fe(Phen)₃](iso-Bu₂PS₂)₂ · 5H₂O (II) were grown. The disulfan {iso-Bu₂P(S)S}₂ (III) was isolated. Compound II consists of the complex cations [Fe(Phen)₃]²⁺, the outer-sphere anions iso-Bu₂PS ₂ ^? , and the molecules of water of crystallization. The coordination polyhedron of the Fe atom is a distorted N₆ octahedron. Complex I is diamagnetic, and thus, the full spin of the Fe²⁺ ion S = 0. The structure of III is built of the molecules containing the S-S bridge 2.061(1) Å in length.     

57Fe Mössbauer spectroscopic and magnetic study of a spin-crossover polymer complex, Fe(3-chloropyridine)2Ni(CN)4

The coordination polymer Fe(3-chloropyridine)₂Ni(CN)₄ (2) has been prepared by a method similar to that for Fe(pyridine)₂Ni(CN)₄ (1). The complex (2) has been characterized by⁵⁷Fe Mössbauer spectroscopy and a SQUID technique.⁵⁷Fe Mössbauer and magnetic susceptibility data show that complex (2) exhibits spin-crossover behavior. The spin transition of (2) occurs between 120 and 80 K with very small hysteresis or without hysteresis. The temperature range of the spin transition in (2) is lower than that in (1). A residual high spin iron(II) fraction is observed at low temperatures in (2), being different from (1). SQUID data also show that samples treated differently yield different spin transition curves.