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31.
A new end-on (EO) azido-bridged tetranuclear copper(II) complex [Cu(4)L(2)(mu(1,1)-N(3))(2)].5H(2)O derived from the ligand H(3)L (N,N'-(2-hydroxylpropane-1,3-diyl)bis-salicylideneimine) has been synthesized. Its X-ray structure shows an unusual Cu(4)O(2)N(2) open cubane core in which four copper(II) atoms are connected two by two through two mu(1,1)-azido species and three by three through two alkoxo bridges. The magnetic susceptibility data is dominated by strong antiferromagnetic interactions associated with the alkoxides and weak ferromagnetic interactions arising from the azides, in agreement with magneto-structural correlations found in the literature relative to such bridges in Cu(II) complexes. 相似文献
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Gerard?A.?van?Albada Aminou?Mohamadou Anna?Maria?Manotti?Lanfredi Ilpo?Mutikainen Urho?Turpeinen Franco?Ugozzoli Jan?ReedijkEmail author 《Journal of chemical crystallography》2005,35(7):541-546
The synthesis, characterization and X-ray structures of two compounds with the general formula trans-M(biz)2(NCS)2 (in which biz = 2,2′-biimidazoline and M = Mn(II) for compound 1 and Ni(II) for compound 2) are reported. Both compounds crystallize in the triclinic space group P-1 with a = 8.393(5), b = 8.946(5), c = 7.659(5) Å, α = 104.440(5), β = 106.880(5), γ = 66.180(5)∘, V = 497.7(5) Å3, Z = 1 for compound 1 and a = 8.155(2), b = 8.8190(10), c = 7.480(2) Å, α = 102.259(15), β = 106.135(13), γ = 67.706(14)∘, V = 474.7(2) Å3, Z = 1 for compound 2.Both metal ions show octahedral coordination with the four nitrogen atoms of two biz ligands in the equatorial plane and the two nitrogen atoms of two isothiocyanate anions in the axial positions. The M–N≡C angles are 166.5(2) and 167.7(2) for compounds 1 and 2, respectively. These values are in the usually obtained range for trans-isothiocyanate coordinated compounds. The sulfur atom of each isothiocyanate anion acts as acceptor for the hydrogen bond with the NH group of the biz ligands. In the IR spectrum the vibrations of the thiocyanate anion are observed at 2090 and 776 cm−1 for compound 1 and at 2108 and 778 cm−1 for compound 2, and these values are typical for linear-bond isothiocyanate complexes of transition metals. 相似文献
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Toledano P Figueiredo Neto AM de Sant'Ana ZA 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(1):486-492
Experimental investigations of lyotropic cholesterics fluids are presented which show that changes in the shape anisotropy and chirality of the micellar population determine the topology of the temperature-concentration phase diagrams. For given amounts of the substances which induce the chirality and modify the shape anisotropy of the micelles, two distinct biaxial cholesteric phases are disclosed in the phase diagrams. This is interpreted in the framework of the catastrophe theory of phase transitions. 相似文献
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García Ruano JL Gamboa AE Gutiérrez LG Martín Castro AM Rodríguez Ramos JH Yuste F 《Organic letters》2000,2(6):733-736
A new kind of chiral dienophiles, cyclic vinyl-p-tolylsulfilimines (2a and 2b), were obtained from the corresponding (Z)-sulfinylacrylonitriles with HBF(4) and methanol. The asymmetric Diels-Alder reaction of optically pure 2a with cyclopentadiene under mild thermal or catalyzed conditions afforded only the endo-4a adduct with complete endo and pi-facial selectivities. The ability of the sulfilimine moiety to enhance the dienophilic reactivity of the double bond is similar to that of the sulfinyl group. 相似文献
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Marcos F.S. Teixeira Bruno H. Freitas Patricia M. Seraphim Leandra O. Salmazo Marcos A. Nobre Silvania Lanfredi 《Procedia Chemistry》2009,1(1):293-296
In the work described by this paper, we studied the development of a selective potassium ion sensor constituted of a carbon paste electrode modified (CPEM) with a novel KSr2Nb2O15. The material KSr2Nb2O15 is an oxide with the tetragonal tungsten bronze structure (TTB) type are in forefront both in the area of research as well as in industrial applications. The sensor response to potassium ions was linear in the concentration range 1.26 x 10-5 at 1.62 x 10-3 mol L-1 (E (mV) = 32.7 + 51.1 log [K+]). The sensor based KSr2Nb2O15, of the TTB-type presented very good potentiometric response, with a slope of 51.1 mV/dec (at 25 °C) and detection limit for the potassium ions of 7.27 x 10-5 mol.L-1. 相似文献