Low-temperature single-crystal Raman and neutron-diffraction study of the hydrogenous ammonium copper(II) Tutton salt and the deuterated analogue in the metastable state

Low-temperature (15 K) single-crystal neutron-diffraction structures and Raman spectra of the salts (NX4)2[Cu(OX2)6](SO4)2, where X=H or D, are reported. This study is concerned with the origin of the structural phase change that is known to occur upon deuteration. Data for the deuterated salt were measured in the metastable state, achieved by application of 500 bar of hydrostatic pressure at approximately 303 K followed by cooling to 281 K and the subsequent release of pressure. This allows for the direct comparison between the hydrogenous and deuterated salts, in the same modification, at ambient pressure and low temperature. The Raman spectra provide no intimation of any significant change in the intermolecular bonding. Furthermore, structural differences are few, the largest being for the long Cu-O bond, which is 2.2834(5) and 2.2802(4) A for the hydrogenous and the deuterated salts, respectively. Calorimetric data for the deuterated salt are also presented, providing an estimate of 0.17(2) kJ/mol for the enthalpy difference between the two structural forms at 295.8(5) K. The structural data suggest that substitution of hydrogen for deuterium gives rise to changes in the hydrogen-bonding interactions that result in a slightly reduced force field about the copper(II) center. The small structural differences suggest different relative stabilities for the hydrogenous and deuterated salts, which may be sufficient to stabilize the hydrogenous salt in the anomalous structural form.     

Temperature dependence of the crystal structure and g-values of [(HC(Ph2PO)3)2Cu](ClO4)2.2H2O: influence of dynamic Jahn-Teller coupling and lattice strain interactions

The temperature dependence of the X-ray crystal structure and powder EPR spectrum of [(HC(Ph(2)PO)(3))(2)Cu](ClO(4))(2).2H(2)O is reported, and the structure at room temperature confirms that reported previously. Below approximately 100 K, the data imply a geometry with near elongated tetragonal symmetry for the [(HC(Ph(2)PO)(3))(2)Cu](2+) complex, but on warming the two higher Cu-O bond lengths and g-values progressively converge, and by 340 K the bond lengths correspond to a compressed tetragonal geometry. The data may be interpreted satisfactorily assuming an equilibrium among the energy levels of a Cu-O(6) polyhedron subjected to Jahn-Teller vibronic coupling and a lattice strain. However, agreement with the experiment is obtained only if the orthorhombic component of the lattice strain decreases to a negligible value as the temperature approaches 340 K.     

The quasi-symmetric OHN and ODN bridges in the adducts of 3,5-dimethylpyridine with 3,5-dinitrobenzoic acid

The crystal structure of the adduct of 3,5-dimethylpyridine and 3,5-dinitrobenzoic acid (DMP-DNB) has been determined at room temperature and 80 K for both undeuterated and deuterated compounds. The monoclinic crystals are isomorphous, space group P2₁/c and Z = 4. Very strong OHN hydrogen bonds are almost linear with fully disordered (1:1) bridge hydrogen atoms between oxygen and nitrogen atoms. This is well reflected in the difference in electron density maps the contours of which depend both on cooling and deuteration. The intramolecular hydrogen bond lengths are 2.550(2) Å for the (OHN) and 2.563(2) Å for (ODN) at room temperature and 2.529(2) Å for (OHN) and 2.531(2) Å for (ODN) at 80 K. Therefore, there is a small but meaningful isotope effect upon the O…N hydrogen bridge length at room temperature and no Ubbelohde isotope effect is observed at 80 K. The infra-red spectra show very broad stretching protonic bands in the 200–1600 cm⁻¹ range. The isotopic ratio v(H)/v(D) at room temperature is about 1.1.     

Direct determination of the anisotropy and exchange splittings in the dimeric single-molecule magnet [Mn4O3Cl4(O2CEt)3(py)3]2.8MeCN by inelastic neutron scattering

Energy splittings resulting from anisotropy and exchange interactions in the dimer of single-molecule magnets [Mn4O3Cl4(O2CEt)3(py)3]2.8MeCN are determined for both an undeuterated and a partially deuterated sample using inelastic neutron scattering. The antiferromagnetic (AF) exchange coupling between the two Mn4 subunits strongly depends on their separation. The Cl...Cl distance between the two subunits can be modified either by exchanging the solvent of crystallization or by deuteration of the C-H...Cl hydrogen bonds. The exchange of acetonitrile for n-hexane leads to a five times greater shortening of the Cl...Cl separation than does full deuteration of all the hydrogen bonds. As a result, the AF exchange coupling constants between the subunits are 0.0073(4) and 0.0103(9) meV in the samples with acetonitrile and n-hexane solvent molecules, respectively, in the crystal structure. On the other hand, the effect of C-H...Cl deuteration on the AF exchange coupling is not detectable within the experimental accuracy of INS.     

Termination and other processes in the polymerization of p-methoxystyrene and 2,2-dideutero-p-methoxystyrene

The uncatalysed thermally initiated free radical bulk polymerization of ?-methoxystyrene and 2,2-dideutero-?-methoxystyrene (65% deuterated) have been studied at 80, 100 and 120°.Both the rate of polymerization and the degree of polymerization are increased by deuteration, as would be expected from the deuterium kinetic isotope effect if disproportionation plays a part in the radical termination process. The effect of deuteration is least at the highest temperature, but it is shown that this does not mean that the extent of disproportionation decreases with increasing temperature.From a comparison of the effect of deuteration on the polymerization rate with its effect on the degree of polymerization, it is concluded that the transfer constant to monomer is less for the deuterated material than for the undeuterated material. It is suggested that the transfer process probably involves the donation of a deuterium or hydrogen atom from the growing radical to the monomer.     

Temperature Dependence of the Crystal Structure and EPR Spectrum of Bis(1,3,5-Trihydroxycyclohexane)copper(II) Tosylate. A Unified Interpretation Using a Model of Dynamic Vibronic Coupling

The crystal structure of bis(1,3,5-trihydroxycyclohexane)copper(II) tosylate is reported at temperatures of 293, 233, 188, 163, and 93 K, as are the structures of the Zn(II) and Ni(II) analogues at room temperature for comparison. The isomorphous compounds are triclinic, space group P&onemacr;, with one formula unit in the unit cell. The unit cell parameters of the Cu compound at 293 K are a = 6.456(5) ?, b = 9.505(3) ?, c = 12.544(3) ?, alpha = 76.57(2) degrees, beta = 87.48(4) degrees, gamma = 76.65(4) degrees. The centrosymmetric ZnO(6) and NiO(6) octahedra are tetragonally compressed with a slight orthorhombic distortion. The Cu(2+) polyhedra exhibit similar geometries, but with considerably larger deviations from a regular octahedron. Two of the three independent Cu-O bond lengths and two of the g-values change significantly as a function of temperature. A model of dynamic vibronic coupling is presented which explains both the EPR and structural data. Vibronic wave functions associated with a Jahn-Teller potential energy surface modified by an orthorhombic lattice "strain" are given. The temperature dependence of the structures is calculated from the nuclear parts and that of the g-values from the electronic parts of the wave functions. The temperature dependence of the structures and g-values is also interpreted using a simpler model involving an equilibrium between two forms of the complex which differ solely in their orientation in the crystal lattice, and the results of the two approaches are compared.     

Vibrational assignment of 4-amino-3-penten-2-one

The infrared and Raman spectra of 4-amino-3-penten-2-one and its two deuterated analogous have been measured. Comparison between the spectra recorded with two techniques, density functional theory (DFT) calculations and the spectral behavior upon deuteration was used for assignment of the vibrational spectra of the titled compound. DFT suggests a relatively strong intramolecular bent hydrogen bond with N...O distance in the range of 2.64-2.67 A, which is in agreement with the observed vNH at 3180 cm(-1). Existence of an intermolecular hydrogen bond is also shown in both solid and solution phases. The spectroscopic data support the enamine structure for this compound rather than imine structure.     

浓度及冷冻-解冻处理对CuCl_2水溶液中Cu~(2+)区域结构的影响

应用扩展X射线吸收精细结构(EXAFS)光谱研究了CuCl2水溶液中Cu2+的区域环境结构,通过测定CuCl2水溶液在不同浓度条件下及冷冻-解冻(FT)处理前后CuK边EXAFS吸收谱,研究了浓度及冷冻-解冻处理对Cu2+第一配位层结构的影响.EXAFS实验结果表明,CuCl2水溶液中Cu2+第一配位层距离中心原子Cu最近邻原子为O原子,配位数介于3.0-4.3之间,Cu—O键长在0.192-0.198nm之间,这种结构与Cu2+的Jahn-Teller效应有关.不同浓度的CuCl2水溶液中Cu2+的区域环境结构有很大不同,随着CuCl2水溶液浓度的升高,Cu2+第一配位层配位数减小,Cu—O键伸长.结构参数拟合结果证实冷冻-解冻处理对Cu2+的区域环境结构有影响,CuCl2溶液经冷冻-解冻处理后,Cu2+第一配位层配位数变大,热无序度增加.     

Stabilizing the elusive ortho-quinone/copper(I) oxidation state combination through pi/pi interaction in an isolated complex

The heterodinuclear compound [(PhenQ)Cu(dppf)](BF4), PhenQ = 9,10-phenanthrenequinone and dppf = 1,1'-bis(diphenylphosphino)ferrocene, was identified structurally and spectroscopically (NMR, IR, UV-vis) as a copper(I) complex of a completely unreduced ortho-quinone. Crystallographic and DFT calculation results suggest that this stabilization of a hitherto elusive arrangement is partially owed to intramolecular pi/pi interactions phenyl/PhenQ. Intermolecular PhenQ/PhenQ pi stacking is also observed in the crystal. According to DFT calculations, the pi interactions are responsible for the considerably distorted coordination geometry at CuI with one short and one longer Cu-O and Cu-P bond, respectively, and with bond angles at copper ranging from 99 degrees to 133 degrees. Electrochemical reduction proceeds reversibly at low temperatures to yield an EPR spectroscopically characterized semiquinone-copper(I) species.     

Nuclear quadrupole resonance studies of hydrogen bonding in trans-dichlorobis(ethylenediamine)cobalt(III) diaquahydrogen chloride

The temperature dependences of the ⁵⁹Co and ligand ³⁵Cl nuclear quadrupole resonance frequencies were measured for trans-[CoCl₂(D₂NC₂H₄ND₂)₂][D₅O₂]Cl₂. The chlorine frequency at 294 K increased by 38.5 kHz over the frequency of the undeuterated complex and only a slight temperature dependence was observed. The increase in the cobalt quadrupole coupling constant over that of the undeuterated complex was 15 kHz at 344 K and reached 252 kHz at 77 K. A weakening of the hydrogen bonds on deuteration is consistent with the shift in the ³⁵Cl NQR frequencies.     

POLARIZED PHOTOACOUSTIC SPECTRA OF PHYCOERYTHRIN and PHYCOCYANIN IN ANISOTROPIC POLYMER FILMS

Abstract— Photoacoustic spectra (PAS) of biliproteins, namely, R-phycoerythrin (PE) and C-phycocyanin (PC) and their mixture in anisotropic and isotropic polyvinylalcohol (PVA) films were measured under the illumination with polarized and natural light. Also samples in deuterated PVA were investigated. The yields of fluorescence of various chromophores of investigated biliproteins were obtained from PAS, absorption, fluorescence and fluorescence lifetime measurements. The deuteration of samples causes different changes in thermal deactivation of excitation of various chromophores. Ratios of PAS to absorption of the light polarized parallel and perpendicular to the direction of film stretching are different. The PAS amplitude of deuterated samples is higher than that for undeuterated.     

Bond Characterization of the 3-D Framework Structure of the Copper(Ⅱ) Isonicotinic Acid Complex Formed by Hydrogen Bonding

The crystal of qudra-aquabis(isonicotinato-N)copper(Ⅱ),Cu[(NC5H4COO)]2 . 4H2O was synthesized via hydrothermal method. Single crystal X-ray analysis at 100K (Siemens SmartCCD) and 25K (Nonius KappaCCD) are performed. The results reveal that the Cu atom is octahedrally coordinated by two Nitrogen atoms of pyridine rings in the axial positions and the four Oxygen atoms of the four water molecules in an equatorial orientation. The octahedral Cu(lI) center shows a large Jahn-Teller distortion with the distances of the Cu-N 2.0253(6)A, Cu-O(3)2.0124(6)~, Cu-O(4) 2.4304(7)A. By means of the hydrogen bonding connections, this compound is formed a 3D framework. In addition, the thermal displacement of each atom at 25K is about three-times smaller than that at 100K. Electron density distribution of this compound at 25K and 100K is also analyzed and compared in terms of multipole model. All topological properties based on X-ray diffraction result and theoretical calculation including the bond critical points (BCP), Laplacian of the electron density and electron density at the BCP will be presented.     

Synthesis, structure, and properties of Cs(4)Th(4)P(4)Se(26): a quaternary thorium selenophosphate containing the (P(2)Se(9))(6-) anion

Orange crystals of Cs(4)Th(4)P(4)Se(26) were grown from the reaction of (232)Th and P in a Cs(2)Se(3)/Se molten salt flux at 750 degrees C. Cs(4)Th(4)P(4)Se(26) crystallizes in the orthorhombic space group Pbca with the unit cell parameters: a = 12.0130(6), b = 14.5747(7), c = 27.134(1) A; Z = 8. The compound exhibits a three-dimensional structure, consisting of dimeric [Th(2)Se(13)] polyhedral units. The two crystallographically independent, nine-coordinate, bicapped trigonal prismatic thorium atoms share a triangular face to form the dimer, and each dimer edge-shares two selenium atoms with two other dimers to form kinked chains along the [010] direction. While this structure shares features of the previously reported Rb(4)U(4)P(4)Se(26), including phosphorus in the 5+ oxidation state, careful inspection of the structure reveals that the selenophosphate anion that knits the structure together in three directions in both compounds is a unique (P(2)Se(9))(6-) anion. The formula may be described best as [Cs(2)Th(2)(P(2)Se(9))(Se(2))(2)](2). The (P(2)Se(9))(6-) anion features a nearly linear Se-Se-Se backbone with an angle of 171 degrees and Se-Se distances that are approximately 0.2-0.3 A longer than the typical single Se-Se bond. Magnetic studies confirm that this phase contains Th(IV). Raman data for this compound is reported, and structural comparisons will be drawn to its uranium analogue, Rb(4)U(4)P(4)Se(26).     

Exchange interactions and electron delocalization in the mixed-valence cluster V(4)(IV)V(2)(V)O(7)(OC(2)H(5))(12)

The mixed-valence cluster compound V4IVV2VO7(OC2H5)12 was studied by X-band electron paramagnetic resonance (EPR) in the temperature range of 4.2-293 K. According to X-ray diffraction study, the crystal structure of the compound was described by a R3m space group at 295 K (four d1 electrons are equally delocalized on all vanadium ions) and changed to a P21/n space group on cooling the crystals to 173 K (the electrons are preferably localized on the four equatorial vanadium ions). The EPR spectra originate from the S = 1 total spin states with the fine structure averaged to a single Lorentzian line and from the S = 2 total spin states with fine structure partly averaged in the temperature range of 295-200 K and well averaged below 45-50 K. The states of S = 1 and S = 2 of comparable energy (DeltaE approximately 2 cm(-1); ES=1 < ES=2) were shown to be the lowest ones. The VIV <--> VV unpaired electron transfers together with isotropic Heisenberg exchange were shown to determine the total spin states composition and the intracluster dynamics of the compound. Two types of electron transfers were assumed: the single-jump transfer leading to the averaged configurations of the V4IVV2V <--> V3IVVV VIVVV type and to the splitting of the total spin states by intervals comparable in magnitude with the isotropic exchange parameter J approximately 100 cm-1 and the double-jump transfer resulting in dynamics. Temperature dependence of the transition rates nutr was observed. In the range of 295-210 K, the value of nutr = (0.5-0.6) x 10(10) s(-1) is sufficient for averaging the fine structure of the S = 1 states, and below 45 K the value of nutr approximately 1.5 x 10(10) s(-1) also averages the fine structure of the S = 2 state. A change in the localization plane of the VIV ions in the temperature range of 40-50 K was discovered.     

Capture of phosphorus(I) and arsenic(I) moieties by a 1,2-bis(arylimino)acenaphthene (aryl-BIAN) ligand. A case of intramolecular charge transfer

The reaction of PCl3 with SnCl2 in THF solution, followed by treatment with dpp-BIAN (dpp = 2,6-i-Pr2C6H3), affords the phosphenium complex [(dpp-BIAN)P][SnCl5.THF]. The 31P chemical shift (delta 232.5) and the metrical parameters from a single-crystal X-ray diffraction study indicate that the oxidation state of phosphorus in this compound is +3. A similar conclusion was reached regarding the phosphorus oxidation state in [(dpp-BIAN)P][I3], which was prepared via the reaction of dpp-BIAN with PI3 in CH2Cl2 solution. The arsenium salt [(dpp-BIAN)As][SnCl5.THF] was prepared by treatment of AsCl3 with SnCl2 in THF solution, followed by the addition of dpp-BIAN. The X-ray crystal structure of this salt was determined, and the pattern of bond distances and angles indicates that arsenic is present in the +3 oxidation state.     

Sulfur X-ray absorption and vibrational spectroscopic study of sulfur dioxide, sulfite, and sulfonate solutions and of the substituted sulfonate ions X3CSO3- (X = H, Cl, F)

Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra have been recorded and the S(1s) electron excitations evaluated by means of density functional theory-transition potential (DFT-TP) calculations to provide insight into the coordination, bonding, and electronic structure. The XANES spectra for the various species in sulfur dioxide and aqueous sodium sulfite solutions show considerable differences at different pH values in the environmentally important sulfite(IV) system. In strongly acidic (pH < approximately 1) aqueous sulfite solution the XANES spectra confirm that the hydrated sulfur dioxide molecule, SO2(aq), dominates. The theoretical spectra are consistent with an OSO angle of approximately 119 degrees in gas phase and acetonitrile solution, while in aqueous solution hydrogen bonding reduces the angle to approximately 116 degrees . The hydration affects the XANES spectra also for the sulfite ion, SO32-. At intermediate pH ( approximately 4) the two coordination isomers, the sulfonate (HSO3-) and hydrogen sulfite (SO3H-) ions with the hydrogen atom coordinated to sulfur and oxygen, respectively, could be distinguished with the ratio HSO3-:SO3H- about 0.28:0.72 at 298 K. The relative amount of HSO3- increased with increasing temperature in the investigated range from 275 to 343 K. XANES spectra of sulfonate, methanesulfonate, trichloromethanesulfonate, and trifluoromethanesulfonate compounds, all with closely similar S-O bond distances in tetrahedral configuration around the sulfur atom, were interpreted by DFT-TP computations. The energy of their main electronic transition from the sulfur K-shell is about 2478 eV. The additional absorption features are similar when a hydrogen atom or an electron-donating methyl group is bonded to the -SO3 group. Significant changes occur for the electronegative trichloromethyl (Cl3C-) and trifluoromethyl (F3C-) groups, which strongly affect the distribution especially of the pi electrons around the sulfur atom. The S-D bond distance 1.38(2) A was obtained for the deuterated sulfonate (DSO3-) ion by Rietveld analysis of neutron powder diffraction data of CsDSO3. Raman and infrared absorption spectra of the CsHSO3, CsDSO3, H3CSO3Na, and Cl3CSO3Na.H2O compounds and Raman spectra of the sulfite solutions have been interpreted by normal coordinate calculations. The C-S stretching force constant for the trichloromethanesulfonate ion obtains an anomalously low value due to steric repulsion between the Cl3C- and -SO3 groups. The S-O stretching force constants were correlated with corresponding S-O bond distances for several oxosulfur species.     

N-邻羟苄亚基苯胺Schiff碱铜配合物的合成、结构和性能表征(英)

The structure of the title compound has been determined by X-ray crystallography. Each copper atom is chelated by two N-salicylidene-aniline anion ligands with Cu-O and Cu-N distances of 0.187 6(3) and 0.200 1(4) nm, respectively. The central copper(Ⅱ) is four-coordinated and in distorted square-planar environment. The phenyl rings with salicylidene moieties form a dihedral angle of 65.40°. There are C-H…π supramolecular interactions in the crystal structure. The title compound is also examined by elemental analysis, FT-IR, UV spectra and TG-DSC analysis. CCDC: 222315.     

Synthesis,Crystal and Molecular Structure of Mono- and Diaquadi(acetato-O)-Bis(2,4′-Bipyridyl) Copper(II)

The title compound has been synthesized and characterized by elemental analysis and conductivity studies. The crystal and molecular structure has been determined. There are two different types of molecules in the crystal: mono- and diaquadi(acetato-O)-bis(2,4'-bipyridyl) copper (II). Both copper atoms occupy special positions. The copper atoms show almost ideal square pyramidal (4 + 1) and square bipyramidal (4 + 2) coordination. Due to the Jahn-Teller effect, the axial Cu-O(water) bond distances are longer than respective equatorial Cu-O(acetate) bond distances. The bond valences of the copper were computed. An intramolecular strong hydrogen bond linking O(water) and O(acetate) atoms exists in the molecule. The differences of geometrical environment for copper in mono- and diaquadi(acetato-O)-bis(2,4'-bipyridyl) copper(II) are imposed by strong intermolecular hydrogen bonds creating a linear infinite chain structure along crystallographic x axis. Also weak intramolecular hydrogen bonds are present in the molecule.     

Proton transfer and a dielectric phase transition in the molecular conductor (HDABCO+)2(TCNQ)3

One-dimensional dielectric (N.H.N)( infinity ) hydrogen-bonding chains of monoprotonated 1,4-diazabicyclo[2.2.2]octane (HDABCO(+)) were introduced into an electrically conducting 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) salt as the countercation structure. Room-temperature electrical conductivity was approximately 10(-)(3) S cm(-)(1), with a semiconductive behavior. The temperature-dependent dielectric constants of (HDABCO(+))(2)(TCNQ)(3) indicated a dielectric transition at 306 K. A large deuterium isotope effect for the dielectric transition (DeltaT = 70 K) was observed for the deuterated salt, (DDABCO(+))(2)(TCNQ)(3). Thermally activated order/disorder of the protons or deuteriums within the one-dimensional hydrogen-bonding chains of (HDABCO(+))( infinity ) and (DDABCO(+))( infinity ) affected the dielectric responses in the TCNQ-based semiconductors.     

Synthesis of a pyridinium bis[citrato(2-)]oxochromate(V) complex and its ligand-exchange reactions

The reaction of citric acid (caH(4)) with pyridinium dichromate (PDC) in anhydrous acetone yields pyridinium bis[citrato(2-)]oxochromate(V), pyH[CrO(caH(2))(2)], as a mixed salt with the Cr(III) product. The compound persists in the solid state for months, is highly soluble in water (pH 4.0), and gives a sharp electron paramagnetic resonance (EPR) signal in solution (g(iso) = 1.9781, A(iso)(Cr) = 17.1 x 10(-4) cm(-1)), which is characteristic of d(1) Cr(V). The presence of [Cr(V)O(caH(2))(2)](-) in the solid state was confirmed by electrospray mass spectroscopy, X-ray absorption near-edge structure (XANES), and EPR spectroscopy. Solid-state EPR spectroscopy, XANES, and a spectrophotometric assay showed that the solid is a mixture of [Cr(V)O(caH(2))(2)](-) and a Cr(III)-citrate complex. The structures of the [Cr(V)O(caH(2))(2)](-) and [Cr(III)(caH(2))(2)](-) components of the mixture were established by multiple-scattering MS analysis of the X-ray absorption fine structure data. The structure of [Cr(V)O(caH(2))(2)](-) is similar to that of other 2-hydroxy acid complexes with Cr=O, Cr-O(alcoholato), and Cr-O(carboxylato) bond lengths of 1.59, 1.81, and 1.90 A, respectively. The Cr(III) complex has bond lengths typical for ligands with deprotonated carboxylate and protonated alcohol donors with distances of 1.90 and 1.99 A, respectively, for the Cr-O(carboxylato) and Cr-O(alcohol) bond lengths. In aqueous solution, [CrO(caH(2))(2)](-) is short lived, but it is a convenient starting material for ligand-exchange reactions. It has been used to generate short-lived mixed-ligand Cr(V) complexes with citrate and picolinate, iminodiacetate, 2,2'-bipyridine, or 1,10-phenanthroline, which were characterized by EPR spectroscopy. The g values are between 1.971 and 1.974. For the picolinate, 2,2'-bipyridine, and 1,10-phenanthroline mixed-ligand complexes, there is hyperfine coupling (2.2 x 10(-4) to 2.4 x 10(-4) cm(-1)) to a single proton of the citrate ligand.