首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The kinetics of the reduction of by Co(dmgBF2)2(H2O)2 in 0.041 M HNO3/NaNO3 was found to be first-order in both the oxidizing and reducing agents and the second-order rate constant is given by kobs = k1 + k2K[Cl], with k1=1.59 × 106 M−1 s−1and k2K = 1.83 × 108 M−2 s−1, at 25 °C. The term that is first-order in [Cl] is attributed to the formation of an ion-pair between and Cl. For k1, the activation parameters ΔH* and ΔS* are 2.22 ± 0.02 kcal mol−1 and −22.7 ± 0.8 cal mol−1 K−1, respectively. The self-exchange rate constant of k22 ≈ 8.7 × 10−3 M−1 s−1 for was estimated using Marcus theory and the known self-exchange rate constant for .  相似文献   

2.
Two new inorganic-organic hybrid polymers [ClBzQl]2[Cd(SCN)3.5Br0.5]·0.25H2O (1) and [ClBzMePy][Cd(SCN)3] (2) (ClBzQl = 1-(4′-Cl-benzyl)quinolinium cation and ClBzMePy = 1-(4′-Cl-benzyl)-2-methylpyridinium cation) have been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Crystal structure analyses show that two polymers belong to the monoclinic space group P2/n (1) and P21/c (2) with a = 18.548(2) Å, b = 9.526(1) Å, c = 20.689(2) Å, β = 94.008(1)°, V = 3646.6(5) Å3 for 1, and a = 11.195(2) Å, b = 16.415(3) Å, c = 10.751(2) Å, β = 102.930(3)°, V = 1925.7(7) Å3 for 2. The Cd atom exhibits a distorted octahedral coordination geometry for 1 and 2. For 1, a pair of 1,1-μ-SCN anions and a pair of 1,3-μ-SCN anions are alternately bridge adjacent Cd centers to form infinite polymeric chains. For 2, adjacent Cd atoms are linked by three 1,3-μ-SCN anions to form infinite [Cd(SCN)3] polymeric chains. The luminescent properties of the two polymers in the solid state at room temperature were investigated.  相似文献   

3.
Reaction of the five-coordinate trigonal-bipyramidal platinum(II) complex, [Pt(pt)(pp3)](BF4) (pt = 1-propanethiolate, pp3 = tris[2-(diphenylphosphino)ethyl]phosphine), with I in chloroform gave the five-coordinate square-pyramidal complex with a dissociated terminal phosphino group and an apically coordinated iodide ion in equilibrium. The thermodynamic parameters for the equilibrium between the trigonal-bipyramidal and square-pyramidal geometries, [Pt(pt)(pp3)]+ + I ? [PtI(pt) (pp3)], and the kinetic parameters for the chemical exchange were obtained as follows: , ΔH0 = − 10 ± 2.4 kJ mol−1, ΔS0 = − 36 ± 10 J K−1 mol−1, , ΔH = 34 ± 4.7 kJ mol−1, ΔS = − 50 ± 21 J K−1 mol−1. The square-planar trinuclear platinum(II) complex was formed by bridging reaction of one of the terminal phosphino groups of trigonal-bipyramidal [PtCl(pp3)]Cl with trans-[PtCl2(NCC6H5)2] in chloroform. From these facts, ligand substitution reactions of [PtX(pp3)]+ (X = monodentate anion) are expected to proceed via an intermediate with a dissociated phosphino group. The rate constants for the chloro-ligand substitution reactions of [PtCl(pp3)]+ with Br and I in chloroform approached the respective limiting values as concentrations of the entering halide ions are increased. These kinetic results confirmed the preassociation mechanism in which the square pyramidal intermediate with a dissociated phosphino group and an apically coordinated halide ion is present in the rapid pre-equilibrium.  相似文献   

4.
α-Amylase from Sorghum bicolor, is reversibly unfolded by chemical denaturants at pH 7.0 in 50 mM Hepes containing 13.6 mM calcium and 15 mM DTT. The isothermal equilibrium unfolding at 27 °C is characterized by two state transition with ΔG (H2O) of 16.5 kJ mol−1 and 22 kJ mol−1, respectively, at pH 4.8 and pH 7.0 for GuHCl and ΔG (H2O) of 25.2 kJ mol−1 at pH 4.8 for urea. The conformational stability indicators such as the change in excess heat capacity (ΔCp), the unfolding enthalpy (Hg) and the temperature at ΔG = 0 (Tg) are 17.9 ± 0.7 kJ mol−1 K−1, 501.2 ± 18.2 kJ mol1 and 337.3 ± 6.9 K at pH 4.8 and 14.3 ± 0.5 kJ mol−1 K−1, 509.3 ± 21.7 kJ mol−1 and 345.4 ± 4.8 K at pH 7.0, respectively. The reactivity of the conserved cysteine residues, during unfolding, indicates that unfolding starts from the ‘B’ domain of the enzyme. The oxidation of cysteine residues, during unfolding, can be prevented by the addition of DTT. The conserved cysteine residues are essential for enzyme activity but not for the secondary and tertiary fold acquired during refolding of the denatured enzyme. The pH dependent stability described by ΔG (H2O) and the effect of salt on urea induced unfolding confirm the role of electrostatic interactions in enzyme stability.  相似文献   

5.
The hydrothermal reaction of CuBr2 and tpyprz in the presence of NH4VO3 and HF for 72 h at 170 °C provided [(tpyprz)3Cu10Br10] (1) in 20% yield. The two-dimensional structure of 1 may be described as Cu(I)-tpyprz chains, linked through {Cu4Br5} clusters in the ac-plane and decorated with {Cu3Br5}2− clusters projecting from one face of the layer in the b-direction. The Cu(I) sites exhibit distorted trigonal coordination {CuBr3} and distorted tetrahedral geometries, {CuBr2N2} and {CuN4}. Crystal data for 1: monoclinic space group C2, a = 12.7561(8) Å, b = 19.359(1) Å, c = 15.860(1) Å, β = 97.178(1)°, V = 3885.8(4) Å3, Z = 2, Dcalc = 2.222 g cm−3, μ(Mo Kα) = 78.75 cm−1.  相似文献   

6.
To characterize driving forces and driven processes in formation of a large-interface, wrapped protein-DNA complex analogous to the nucleosome, we have investigated the thermodynamics of binding the 34-base pair (bp) H′ DNA sequence to the Escherichia coli DNA-remodeling protein integration host factor (IHF). Isothermal titration calorimetry and fluorescence resonance energy transfer are applied to determine effects of salt concentration [KCl, KF, K glutamate (KGlu)] and of the excluded solute glycine betaine (GB) on the binding thermodynamics at 20 °C. Both the binding constant Kobs and enthalpy ΔH°obs depend strongly on [salt] and anion identity. Formation of the wrapped complex is enthalpy driven, especially at low [salt] (e.g., ΔHoobs = − 20.2 kcal·mol− 1 in 0.04 M KCl). ΔH°obs increases linearly with [salt] with a slope (dΔH°obs/d[salt]), which is much larger in KCl (38 ± 3 kcal·mol− 1 M− 1) than in KF or KGlu (11 ± 2 kcal·mol− 1 M− 1). At 0.33 M [salt], Kobs is approximately 30-fold larger in KGlu or KF than in KCl, and the [salt] derivative SKobs = dlnKobs/dln[salt] is almost twice as large in magnitude in KCl (− 8.8 ± 0.7) as in KF or KGlu (− 4.7 ± 0.6).A novel analysis of the large effects of anion identity on Kobs, SKobs and on ΔH°obs dissects coulombic, Hofmeister, and osmotic contributions to these quantities. This analysis attributes anion-specific differences in Kobs, SKobs, and ΔH°obs to (i) displacement of a large number of water molecules of hydration [estimated to be 1.0(± 0.2) × 103] from the 5340 Å2 of IHF and H′ DNA surface buried in complex formation, and (ii) significant local exclusion of F and Glu from this hydration water, relative to the situation with Cl, which we propose is randomly distributed. To quantify net water release from anionic surface (22% of the surface buried in complexation, mostly from DNA phosphates), we determined the stabilizing effect of GB on Kobs: dlnKobs/d[GB]  = 2.7 ± 0.4 at constant KCl activity, indicating the net release of ca. 150 H2O molecules from anionic surface.  相似文献   

7.
Two new one-dimensional azido-bridged chiral copper(II) coordination polymers, [(μ-1,1,3-N3)2{Cu2(R-L)2(N3)2}]n (1) (R-L = R-2-(N-(2-hydroxybutyl)carbaldimino) pyridine) and [(μ-1,1,3-N3)2{Cu2(S-L)2(N3)2}]n (2) (S-L = S-2-(N-(2-hydroxybutyl)carbaldimino)pyridine) have been synthesized and structurally characterized. Complexes 1 and 2 crystallize in the monoclinic chiral space group P21. For 1, with a = 6.9565(17) Å, b = 20.675(5) Å, c = 9.859(2) Å, β = 105.944(5)° and Z = 2. In the case of compound 2, a = 6.9650(17) Å, b = 20.705(5) Å, c = 9.878(2) Å, β = 105.941(4)° and Z = 2. Both complexes consist of one-dimensional chiral structures in which the copper(II) ions with a distorted octahedral geometry are interlinked by the unusual μ-1,1,3 azido ligands. Circular dichroism spectra demonstrate that 1 and 2 are a pair of enantiomers. Their magnetic properties have been studied. Fitting of the susceptibility data for 1 and 2 using the Bleany-Bowers expression derived from the isotropic spin-exchange Hamiltonian H = −2JS1S2 leads to the parameters g = 2.21, J = −2.06 cm−1, zJ′ = −0.0309 cm−1 and R = 4.0 × 10−4.  相似文献   

8.
Self-assembly reaction of Cd(ClO4)2 · 6H2O with Norfloxacin (H-Norf) affords a novel 2D rectangular grid framework [Cd(Norf)(ClO4)(H2O)] (1) with strong blue luminescent emission (λem=425 nm), while Norf acts as a tetradentate bridging linker to connect three Cd centers and ClO4 − completes Cd center octahedron coordination geometry. The compound 1 has crystallographic data of triclinic, space group , a=9.4577(1) Å, b=9.5012(2) Å, c=12.2805(1) Å, V=3624.4(3) Å3, Z=2.  相似文献   

9.
Synthesis, crystal structures, and spectroscopic and magnetic properties of new one-dimensional cyano-bridged bimetallic complexes, [CuII(N-Eten)2][MII(CN)4] (N-Eten = N-ethylethylenediamine; MII = NiII (1) and PtII (2)), have been reported. Both complexes consist of one-dimensional alternate chains of CuII and MII moieties. The Pt-C bond distances of 1.997(3) and 2.001(3) Å for 2 are considerably longer than the Ni-C bond lengths of 1.866(3) and 1.872(3) Å for 1. Because of pseudo Jahn-Teller distortion, the axial Cu-N bond distances of 2.554(2) and 2.550(3) Å for 1 and 2 are longer than those of equatorial ones of 2.008(2) and 2.056(2) Å for 1 and 2.010(2) and 2.054(2) Å for 2. In contrast to MII-C bond distances, the Cu-N ones of 1 are similar to those of 2 regardless of element-substitution. These complexes indicate weak antiferromagnetic interactions with Weiss constants = − 4.68 and −3.95 K for 1 and 2, respectively. The emission spectrum of 2 (λex = 360 nm) exhibits a broad band with peaks at 22 800 and 24 000 cm−1 at 298 K. The Cu 2p1/2 and 2p3/2 peaks of XPS spectra are compared systematically to various copper(II) complexes showing different bridging features or distorted coordination geometries as models for excited structures induced by external physical conditions. The spectroscopic properties are discussed from the viewpoint of magneto-optical properties.  相似文献   

10.
Arjun Tiwari 《BBA》2009,1787(8):985-994
This study provides evidence for the superoxide oxidase and the superoxide reductase activity of cytochrome b559 (cyt b559) in PSII. It is reported that in Tris-treated PSII membranes upon illumination, both the intermediate potential (IP) and the reduced high potential (HPred) forms of cyt b559 exhibit superoxide scavenging activity and interconversion between IP and HPred form. When Tris-treated PSII membranes were illuminated in the presence of spin trap EMPO, the formation of superoxide anion radical (O2) was observed, as confirmed by EPR spin-trapping spectroscopy. The observations that the addition of enzymatic (superoxide dismutase) and non-enzymatic (cytochrome c, α-tocopherol and Trolox) O2 scavengers prevented the light-induced conversion of IP ↔ HPred cyt b559 confirmed that IP and HPred cyt b559 are reduced and oxidized by O2, respectively. Redox changes in cyt b559 by an exogenous source of O2 reconfirmed the superoxide oxidase and reductase activity of cyt b559. Furthermore, the light-induced conversion of IP to HPred form of cyt b559 was completely inhibited at pH > 8 and by chemical modification of the imidazole ring of histidine residues using diethyl pyrocarbonate. We proposed that a change in the environment around the heme iron, induced by the protonation and deprotonation of His22 residue generates a favorable condition for the oxidation and reduction of O2, respectively.  相似文献   

11.
The reaction of the organolutetium complex (CGC′)LuCl3Li2(THF), (1; CGC′ = [Me2Si(3-pyrrolidinyl-1-η5-indenyl)(tBuN)]2−) with NaN(TMS)2 provides a straightforward route to the halide-free organolutetium amido complex, (CGC′)LuN(TMS)2(THF) (2). These new complexes were characterized by standard analytical methodology. The monomeric complex 2 crystallizes in the monoclinic space group P21/c with four molecules in a cell of dimensions a = 11.1566(6) Å, b = 14.9805(8) Å, c = 22.18007(12) Å, and β = 90.0620(10)°. Complex 2 is an active precatalyst for the intramolecular hydroamination/cyclization of representative aminoalkenes with turnover frequencies as high as 205 h−1 at room temperature.  相似文献   

12.
A hexarhenium cyanohydroxo anionic cluster complex [Re6Se8(CN)4(OH)2]4− was synthesized for the first time starting from [Re6Se8(OH)6]4−, which was crystallized as a salt of the composition Cs2.75K1.25[Re6Se8(CN)4(OH)2]·H2O (1). The reaction of the complex with Cu2+ in an aqueous ammonia or methylamine solutions afforded [Cu(NH3)5]2[Re6Se8(CN)4(OH)2]·8H2O (2) or [{Cu(CH3NH2)4}2Re6Se8(CN)4(OH)2] (3), respectively. All of these three compounds were characterized by a single-crystal X-ray diffraction method. Compound 1 is crystallized in the tetragonal space group I4/m with eight formula units per cell (a = b = 17.4823(14) Å, c = 19.430(2) Å, V = 5938.3(10) Å3); compound 2 is crystallized in the monoclinic space group P21/n with two formula units per cell (a = 12.1845(13) Å, b = 8.6554(9) Å, c = 19.2568(19) Å, β = 91.081(2)°, V = 2030.5(4) Å3); compound 3 is crystallized in the orthorhombic space group Cmcm with four formula units per cell (a = 19.816(4) Å, b = 14.611(3) Å, c = 13.751(3) Å, V = 3981.2(13) Å3). The luminescence properties of 1 were studied in both aqueous solution and solid state. In addition, the electronic structure of [Re6Se8(CN)4(OH)2]4− was elucidated by DFT calculations.  相似文献   

13.
The syntheses, structures, and magnetic properties of two new μ-alkoxo-μ-pyrazolato heterobridged compounds, [Cu II2(L1-F)(μ-prz)] (1) and [Cu II2(L1-2OMe) (μ-prz)] · 0.5 CH3CN (2) (prz=pyrazolato; H2L1-F=1,3-bis(3-fluorosalicylideneamino)-2-propanol; H2L1-2OMe=1,3-bis(4,6-dimethoxy salicylideneamino)-2-propanol) have been reported. Compound 1 crystallizes in triclinic space group with a=8.6392(10) Å, b=10.6431(9) Å, c=11.6809(13) Å, α=85.972(8)°, β=71.492(9)°, and γ=72.221(9)°, while the unit cell parameters of 2 are as follows: space group: monoclinic C2/c, a=28.2948(5) Å, b=7.3033(2) Å, c=26.3933(5) Å, and β=96.243(1)°. The variable-temperature magnetic susceptibility measurements reveal that the metal centers in both the compounds are antiferromagnetically coupled with J=−200 cm−1 for 1 and J=−175 cm−1 for 2. The magnetic behaviors have been explained on the basis of two opposing factors, complementarity and countercomplementarity of magnetic orbitals.  相似文献   

14.
By varying the solvents and temperatures under solvothermal conditions, two new magnesium based coordination networks were synthesized using 2,5-thiophenedicarbxoylate as a linker. Mg3(TDC)3(DMF)3 [1; TDC = 2,5 thiophenedicarboxylate; space group P21/c, a = 17.747(4) Å, b = 9.805(2) Å, c = 21.359(4) Å, β = 103.13(3)°] is constructed by a combination of magnesium polyhedral trimers, which are connected by the TDC2− linkers to form a 3-D network. Coordinated DMF molecules are present within the channels. Mg(TDC)(H2O)2 [2; space group Pnma, a = 7.296(4) Å, b = 17.760(4) Å, c = 6.6631(3) Å] is formed by 1-D chains of magnesium octahedra connected by the TDC2− linker. Water molecules are coordinated at the axial positions of the magnesium octahedra. Compound 1 is formed using DMF as the synthesis solvent at 180 °C, while compound 2 is formed using ethanol as the synthesis solvent at 100 °C. Both compounds show enhanced photoluminescence intensity when excited at 397 nm compared to the free TDC ligand, suggesting a charge transfer between the ligand and the magnesium metal center.  相似文献   

15.
Reaction of fresh Mn(OH)2 precipitate and S-carboxymethyl-l-cysteine (H2SCMC) in aqueous solution afforded a novel chiral 3D coordination polymer Mn(H2O)(SCMC) 1, which crystallizes in the acentric polar space group P21 with cell constants = 5.079(1) Å, = 9.617(2) Å, = 8.649(2) Å, β = 94.40(3)°, = 421.2(1) Å3, = 2, and exhibit a SHG effect and ferroelectricity (a remnant polarization Pr = 0.0159 uC cm−2, coercive field Ec = 0.83 kV cm−2, saturation of the spontaneous polarization Ps = 0.234 uC cm−2). To the best of our knowledge, the present compound represents the first example of S-carboxymethyl-l-cysteine coordination polymers that exhibit possible ferroelectric behavior. The structural analysis revealed that the Mn2+ ions in 1 are each coordinated by one N atom and five O atoms of four S-carboxymethyl-l-cysteine ligand bridges four symmetry-related Mn2+ ions to form 3D MOF of 66 topology type with irregular chiral channels extending along [1 0 0]. The temperature-dependent magnetic susceptibilities shows that 1 obeys Curie-Weiss law χm = C/(T − Θ) with C = 4.23 cm3 mol−1 K and Θ = −5.86 K and the best fit gave a weak antiferromagnetic coupling (J = −0.282(5) cm−1) among Mn ions.  相似文献   

16.
A new one-dimensional copper(II) polymer, [Cu4(dmapox)2(SCN)4(CH3CH2OH)2]n · 2nCH3CH2OH, where dmapox is the dianion of N,N′-bis[3-(dimethylamino)propyl]oxamide, was synthesized and characterized by elemental analysis, conductivity measurement, IR and electronic spectral studies. The crystal structure of the copper(II) complex has been determined by X-ray single-crystal diffraction. The complex crystallizes in triclinic, space group and exhibits infinite one-dimensional copper(II) polymeric chain bridged both by the bis-tridentate μ-trans-dmapox and μ-1,3-thiocyanate ligands. The environment around the copper(II) atom can be described as distorted square-pyramid. The Cu···Cu separations through μ-trans-oxamidate and thiocyanate bridges are 5.245(5) Å (Cu1-Cu1i)(i = −x+1, −y, −z+1), 5.262(4) Å (Cu2-Cu2ii)(ii = −x,−y, −z+1) and 6.022(3) Å (Cu1-Cu2), respectively. The interaction of the copper(II) complex with herring sperm DNA (HS-DNA) has been investigated by using absorption and emission spectral and electrochemical techniques and viscometry. The results reveal that the copper(II) complex interacts with the DNA in the mode of groove binding with the intrinsic binding constant of 2.38 × 105 M−1.  相似文献   

17.
The role of relativistic effects (RE) in the structures of Cd(II) complexes with crown ethers, and the reason the ‘soft’ Cd(II) strongly prefers to bind to SCN through N, are considered. The synthesis and structures of [Cd(18-crown-6)(thiourea)2] (ClO4)2.18-crown-6 (1) and [Cd(Cy2-18-crown-6)(NCS)2] (2) are reported. (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; Cy2-18-crown-6 = cis-anti-cis-2,5,8,15,18,21-hexaoxatricylo[20.4.0.0(9,14)]hexacosane). In 1 Cd is coordinated in the plane of the crown which has close to D3d symmetry, with long Cd-O bonds averaging 2.688 Å. The two thiourea molecules form relatively short Cd-S bonds that average 2.468 Å, with an S-Cd-S angle of 164.30°. This structure conforms with the idea that Cd(II) can adopt a near-linear structure involving two covalently-bound donor atoms (the S-donors) with short Cd-S bonds, which resembles gas-phase structures for species such as CdCl2. The structure of 2 is similar, with the two SCN ligands N-bonded to Cd, with short Cd-N bonds of 2.106 Å, and N-Cd-N angle of 180°. The crown in 2 forms long Cd-O bonds that average 2.698 Å. Molecular mechanics calculations suggest that a main reason Cd(II) prefers to bind to SCN through N is that when bound through S, the small Cd-S-C angle, which is typically close to 100°, brings the ligand into close contact with other ligands present, and causes steric destabilization. In contrast, the Cd-N-C angles for SCN coordinated through N are much larger, being 171.4° in 2, which keeps the SCN groups well clear of the crown ether. DFT (density functional theory) calculations are used to generate the structures of [Cd(18-crown-6)(H2O)2]2+ (3) and [Cd(18-crown-6)Cl2] (4). In 3, the Cd(II) is bound to only three O-donors of the macrocycle, with Cd-O bonds averaging 2.465 Å. The coordinated waters form an O-Cd-O angle of 139.47°, with Cd-O bonds of 2.295 Å. In contrast, for 4, the Cd is placed centrally in the cavity of the D3d symmetry crown, with long Cd-O bonds averaging 2.906 Å. The Cl groups form a Cl-Cd-Cl angle of 180°, with short Cd-Cl bonds of 2.412 Å. With ionically bound groups on the axial sites of[Cd(18-crown-6)X2] complexes, such as with X = H2O in 3, the Cd(II) does not adopt linear geometry involving the two X groups, with long Cd-O bonds to the O-donors of the macrocycle. With covalently-bound X = Cl in 4, short Cd-Cl bonds and a linear [Cl-Cd-Cl] unit results, with long Cd-O bonds to the crown ether.  相似文献   

18.
A dinickel(II) complex [Ni2(sym-hmp)2](BPh4)2·3.5DMF·0.5(2-PrOH) (1) was synthesized with a dinucleating ligand, 2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methyl-phenol [H(sym-hmp)]. The complex 1 (C90H118.50B2N7.50Ni2O10) crystallized in the triclinic space group with dimensions = 14.7446(4) Å, = 15.4244(4) Å, = 18.7385(6) Å, α = 86.9495(9)°, β = 76.7263(10)°, γ = 86.5370(8)°, and = 4136.8(2) Å3 and with = 2; this is isomorphous to a previous cobalt(II) complex [Co2(sym-hmp)2](BPh4)2. Single-crystal X-ray analysis revealed a bis(μ-phenoxo)dinickel(II) core structure containing two distorted octahedral nickel(II) ions of C2 symmetry. The order of the coordination bond lengths is Ni-O(phenoxo) < Ni-O(hydroxy) < Ni-N. The electronic spectrum of 1 was typical for the octahedral nickel(II) complexes, but the axial elongation and the C2-twist of the equatorial plane were found after a detailed analysis. The bond angles obtained by the electronic spectrum agreed with the crystallographically obtained bond angles within 2.3°. The order of the AOM parameters was eσ,O(phenoxo) > eσ,O(hydroxy) > eσ,N, which was consistent with the order of the coordination bond lengths. Magnetic susceptibility data for 1 were fitted well with the parameters 2= −69.7 cm−1, = 0.00 cm−1, = 2.17, and TIP = 265 × 10−6 cm3 mol−1. The result indicates significant antiferromagnetic exchange interaction and negligible zero-field splitting, while the isostructural cobalt(II) complex showed an anisotropic behavior.  相似文献   

19.
Diflorasone diacetate, a steroid anti-inflammatory drug (marketed as Diacort® or Florone® by Pfizer) and used in the treatment of skin disorders, can be prepared as anhydrous form, DD1 (as deposited in the US pharmacopoeia), or as a monohydrated phase, DDW. Heating the DDW form above 90 °C, a mixture of DD1 and of a new anhydrous polymorph, DD2 is obtained. Further heating of this mixture, or of pure DD1, up to 230 °C (only a few degrees before melting!), generates an elusive anhydrous DD3 polymorph. Their crystal structures, determined uniquely from laboratory powder diffraction data, show the isomorphous character of the DDW and DD1 forms, while the DD2 and DD3 polymorphs crystallize with markedly different unit cells. Crystals of the DD1, DD2 and DDW forms are orthorhombic, P212121, a = 29.386(1) Å; b = 10.4310(9) Å, c = 8.1422(7) Å, V = 2495.8(3) Å3 for DD1; a = 15.2639(10) Å; b = 11.7506(7) Å, c = 13.8931(11) Å, V = 2491.9(3) Å3 for DD2; a = 30.311(2) Å; b = 10.6150(9) Å, c = 7.9337(7) Å, V = 2552.7(4) Å3 for DDW; while the lattice parameters for the monoclinic P21DD3 species are a = 11.5276(10) Å; b = 13.8135(11) Å, c = 7.8973(7) Å, β = 103.053(6)°, V = 1225.0(2) Å3. These compounds have also been fully characterized by thermo analytical methods, as well by 13C, 19F, and 1H NMR spectroscopy.  相似文献   

20.
The ligand substitution reaction of Ru2(O2CCH3)4Cl with 2-amino-4,6-dimethylpyrimidine (Hadmpym) under gentle refluxing conditions in methanol led to the formation of a bridging-ligand mono-substituted compound, [Ru2(O2CCH3)3(admpym)(Cl)(MeOH)] (1). Compound 1 crystallized in monoclinic space group P21/n (no. 14) with a=8.3074(8) Å, b=12.3722(8) Å, c=18.913(1) Å, β=95.559(3)°, V=1934.8(3) Å3, and Z=4. Temperature dependence of the magnetic susceptibility of 1 revealed it to be in a spin ground state S=3/2 arising from the electronic configuration of σ2π4δ2(δ*π*)3. Compound 1 undergoes three metal-centered redox reactions in electrochemistry: E1/2 (ox)=+0.72 V (Ia/Ic<1, ΔEp=0.17 V); E1/2 (1,red)=−0.65 V (Ia/Ic≈1, ΔEp=0.10 V); and E1/2 (2,red)=−1.80 V (Ia/Ic?1, ΔEp=0.16 V). Then, the redox species produced by electrolysis were characterized by spectroscopic studies.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号