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21.
Malykhina L. V. Prosvirin A. V. Haase W. Galyametdinov Yu. G. 《Russian Chemical Bulletin》2001,50(3):488-493
The reaction of Schiff"s base L with lanthanide alkylsulfates affords liquid crystalline complexes with the general formula L3Ln(CnH2n+1OSO3)3. The liquid crystalline structure and magnetic properties are studied by polarization thermal microscopy, differential scanning calorimetry, X-ray diffraction, and measurement of magnetic susceptibility. The temperatures of the existence of the mesophase and magnetic anisotropy of the complexes with the same lanthanide depend on the chain length of the alkyl fragment in the sulfate anion. 相似文献
22.
23.
Boca R Boca M Dlhán L Falk K Fuess H Haase W Jarosciak R Papánková B Renz F Vrbová M Werner R 《Inorganic chemistry》2001,40(13):3025-3033
The spin crossover system, [Fe(bzimpy)(2)](ClO(4))(2).0.25H(2)O, was reinvestigated above room temperature (bzimpy = 2,6-bis(benzimidazol-2-yl)pyridine). The system exhibits an abrupt low-spin to high-spin transition at T(c) = 403 K. Liberation of a fractional amount of water does not affect the spin crossover: the system is perfectly reversible with a hysteresis width of DeltaT = 12 K. The existence of the hysteresis at such high temperature determines that the lowest limit of the solid-state cooperativity parameter is J/k > 403 K despite long iron(II) separations (10 A). The high cooperativeness has been assigned to a perfect pi-stacking of the benzimidazole rings in the crystal lattice at a distance as short as 3.6 A. Variable-temperature IR data and the heat capacity measurements match well the magnetic data. The thermodynamic properties are DeltaH = 17 kJ mol(-)(1), DeltaS = 43 J K(-)(1) mol(-)(1), so that the entropy of the spin transition shows a considerable contribution from the molecular vibrations. A theoretical model has been applied in fitting the magnetic data along the whole hysteresis path. A statistical distribution of the cooperativity parameter led to the feature that angled walls of the hysteresis loop are well reproduced. 相似文献
24.
25.
W. Haase 《无机化学与普通化学杂志》1974,404(3):273-283
The Crystal and Molecular Structure of Jodo-bis-[2-(diphenylphosphinomethyl)pyridine]nickel(II)-jodide, which is a Diamagnetic, Square-pyramidal Complex with d8-Configuration The crystal and molecular structure of the title compound has been determined by single-crystal X-ray methods with 5119 independent reflextions and refined to R = 0.061 for 4321 observed reflections. The crystals are monoclinic, space group P21/n, a = 9.016 ± 0.005, b = 21.612 ± 0.012, c = 17.871 ± 0.010 Å, with and β = 96.32 ± 0.15°; Z = 4. The structure was solved by PATTERSON and FOURIER methods and refined by least squares. The molecule cation has approximate Cs-symmetry. The co-ordination around the nickel atom is approximate square pyramidal with two nitrogen and two phosphorus atoms in the basal plane and the jodine atom in the apex. The Ni? J-distance with 3.047(3) Å is very long. In the basal plane, the nitrogen and phosphorus atoms have cis configuration and the geometric arrangements by the two chelate-5-rings are different. The mean Ni? N(1.963(13)Å) and Ni? P(2.166(5)Å) bond lengths are considerably 0.05 longer and 0.10 Å shorter respectively than the corresponding covalent bonding values, derived from the sum of the covalent radii. 相似文献
26.
R. Haase U. Illgen J. Scheve I. W. Schulz 《Reaction Kinetics and Catalysis Letters》1985,28(2):395-400
The formation of needle shaped crystallites of V6O13 at low V concentrations on V2O5-anatase coated catalysts explains the low selectivity for phthalic anhydride during o-xylene oxidation. The (010) plane of V-oxide, most active for selective oxidation of o-xylene, is not accessible and the contact of this plane with the anatase faces promotes the anatase-rutile transformation and the incorporation and blocking of V4+ ions.
V6O13 V , V2O5-, -. (010) , -, , - V+4.相似文献
27.
Dutta SK Werner R Flörke U Mohanta S Nanda KK Haase W Nag K 《Inorganic chemistry》1996,35(8):2292-2300
A series of heterobimetallic complexes of the type [Fe(III)M(II)L(&mgr;-OAc)(OAc)(H(2)O)](ClO(4)).nH(2)O (2-5) and [{Fe(III)Co(III)L(&mgr;-OAc)(OAc)}(2)(&mgr;-O)](ClO(4))(2).3H(2)O (6) where H(2)L is a tetraaminodiphenol macrocyclic ligand and M(II) = Zn(2), Ni(3), Co(4), and Mn(5) have been synthesized and characterized. The (1)H NMR spectrum of 6 exhibits all the resonances between 1 and 12 ppm. The IR and UV-vis spectra of 2-5 indicate that in all the cases the metal ions have similar coordination environments. A disordered crystal structure determined for 3 reveals the presence of a (&mgr;-acetate)bis(&mgr;-phenoxide)-Ni(II)Fe(III) core, in which the two metal ions have 6-fold coordination geometry and each have two amino nitrogens and two phenolate oxygens as the in-plane donors; aside from the axial bridging acetate, the sixth coordination site of nickel(II) is occupied by the unidentate acetate and that of iron(III) by a water molecule. The crystal structure determination of 6 shows that the two heterobinuclear Co(III)Fe(III) units are bound by an Fe-O-Fe linkage. 6 crystallizes in the orthorhombic space group Ibca with a = 17.577(4) ?, b = 27.282(7) ?, c = 28.647(6) ?, and Z = 8. The two iron(III) centers in 6 are strongly antiferromagnetically coupled, J = -100 cm(-1) (H = -2JS(1).S(2)), whereas the other two S(1) = S(2) = (5)/(2) systems, viz. [Fe(2)(III)(HL)(2)(&mgr;-OH)(2)](ClO(4))(2) (1) and the Fe(III)Mn(II) complex (5), exhibit weak antiferromagnetic exchange coupling with J = -4.5 cm(-1) (1) and -1.8 cm(-1) (5). The Fe(III)Ni(II) (3) and Fe(III)Co(II) (4) systems, however, exhibit weak ferromagnetic behavior with J = 1.7 cm(-1) (3) and 4.2 cm(-1) (4). The iron(III) center in 2-5 exhibits quasi-reversible redox behavior between -0.44 and -0.48 V vs Ag/AgCl associated with reduction to iron(II). The oxidation of cobalt(II) in 4 occurs quasi-reversibly at 0.74 V, while both nickel(II) and manganese(II) in 3 and 5 undergo irreversible oxidation at 0.85 V. The electrochemical reduction of 6 leads to the generation of 4. 相似文献
28.
29.
Kraft S Hanuschek E Beckhaus R Haase D Saak W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(3):969-978
This paper reports on the potential of titanium compounds as building blocks for supramolecular polygons. Self-assembly reactions of low-valent titanocene units and N-heterocyclic bridging ligands lead to novel titanium-based supramolecular squares. Pyrazine (3), 4,4'-bipyridine (4), and tetrazine (5) were used as bridging ligands, and the acetylene complexes [Cp2Ti{eta2-C2(SiMe3)2}] (1) and [(tBuCp)2Ti{eta2-C2(SiMe3)2}] (2) as sources of titanocene fragments. Molecular rectangles can be synthesized by stepwise reduction of the titanocene dichlorides [Cp(2)TiCl2] and [(tBuCp)2TiCl2] and consecutive coordination of two different bridging ligands. The resulting complexes are the first examples of molecular rectangles containing bent metallocene corner units. Single-crystal X-ray analyses of the tetranuclear compounds revealed the geometric properties of the molecular polygons in the solid state. Comparison of bond lengths and angles in coordinated and free ligands reveals the reduced state of the bridging ligand in the low-valent titanium compounds. The syntheses and properties of these novel, highly air- and moisture-sensitive compounds are discussed. 相似文献
30.
Abstract The long range molecular dynamical behaviour of liquid-crystalline side chain polymers with the mesogenic groups linked laterally to the backbone have been studied by using dielectric relaxation spectroscopy over a broad temperature and frequency range. The samples were oriented homeotropically and homogenously by electric and magnetic fields and the relaxations were recorded during alignment and with the fully aligned samples. By fitting the data to theoretical relaxation curves, accurate relaxation parameters could be determined, allowing us to perform a comparison with end-fixed liquid-crystalline side chain polymers on the one hand and with low molecular weight liquid crystals on the other. The relaxation in homeotropic alignment for the laterally fixed compound has more analogies in some aspects, for example, the relaxation time distribution, with low molecular weight liquid crystals than with the corresponding end-fixed compounds, though the activation energy is very large (241 kJ/mol). We relate this to the length of the rigid mesogenic unit and the resulting stronger repulsion by the neighbouring side chains during reorientation. In homogeneous alignment the relaxation is very broad and also has a large activation energy. Different molecular processes are related to this relaxation regime. The relationship between the different relaxation processes and the molecular structure is discussed. 相似文献