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31.
Lorena M. CallejoNoelia De la Pinta Gotzon MadariagaLuis Lezama M. Luz FidalgoRoberto Cortés 《Polyhedron》2011,30(6):923-928
Here we report the synthesis and characterization by X-ray diffraction, FTIR, UV-Vis and EPR spectroscopies, and the magnetic measurements of two new compounds: [Mn(NCS)2(bpe)2(H2O)2] (1) and [Fe(NCS)2(bpe)2(H2O)2] (2) (bpe = 1,2-bis(4-pyridyl)ethylene). Single-crystal structure analyses reveals discrete octahedral metal units that are assembled into 2D sheets through O-Hw?N(bpe) and O-Hw?S(thiocyanate) hydrogen bonds. The intermetallic M?M distances are 6.90 and 6.87 Å for 1 and 2, respectively. Supramolecular architectures are obtained by connections through H-bonds. Slight interactions are observed for compound 2. 相似文献
32.
Rosas F Maldonado A Lezama J Domínguez RM Mora JR Cordova T Chuchani G 《The journal of physical chemistry. A》2012,116(2):846-854
The gas-phase thermal elimination of 2,2-diethoxypropane was found to give ethanol, acetone, and ethylene, while 1,1-diethoxycyclohexane yielded 1-ethoxycyclohexene and ethanol. The kinetics determinations were carried out, with the reaction vessels deactivated with allyl bromide, and the presence of the free radical suppressor cyclohexene and toluene. Temperature and pressure ranges were 240.1-358.3 °C and 38-102 Torr. The elimination reactions are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are given by the following Arrhenius equations: for 2,2-diethoxypropane, log k(1) (s(-1)) = (13.04 ± 0.07) - (186.6 ± 0.8) kJ mol(-1) (2.303RT)(-1); for the intermediate 2-ethoxypropene, log k(1) (s(-1)) = (13.36 ± 0.33) - (188.8 ± 3.4) kJ mol(-1) (2.303RT)(-1); and for 1,1-diethoxycyclohexane, log k = (14.02 ± 0.11) - (176.6 ± 1.1) kJ mol(-1) (2.303RT)(-1). Theoretical calculations of these reactions using DFT methods B3LYP, MPW1PW91, and PBEPBE, with 6-31G(d,p) and 6-31++G(d,p) basis set, demonstrated that the elimination of 2,2-diethoxypropane and 1,1-diethoxycyclohexane proceeds through a concerted nonsynchronous four-membered cyclic transition state type of mechanism. The rate-determining factor in these reactions is the elongation of the C-O bond. The intermediate product of 2,2-diethoxypropane elimination, that is, 2-ethoxypropene, further decomposes through a concerted cyclic six-membered cyclic transition state mechanism. 相似文献
33.
In this paper we prove that if D is a Prüfer domain such that given a proper invertible integral ideal A of D there exists a nonempty finite set of finitely generated maximal ideals that contain A, then D has the simultaneous basis property. This result is used to study two old open problems: "Does every Prüfer domain have the PA-property?", and "Is every Bézout domain an elementary divisor domain?". We include also a new different proof of the simultaneous basis property for valuations domains. 相似文献
34.
35.
Kinetic and Mechanisms of the Homogeneous,Unimolecular Elimination of Phenyl Chloroformate and p‐Tolyl Chloroformate in the Gas Phase
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The gas‐phase elimination of phenyl chloroformate gives chlorobenzene, 2‐chlorophenol, CO2, and CO, whereasp‐tolyl chloroformate produces p‐chlorotoluene and 2‐chloro‐4‐methylphenol CO2 and CO. The kinetic determination of phenyl chloroformate (440–480oC, 60–110 Torr) and p‐tolyl chloroformate (430–480°C, 60–137 Torr) carried out in a deactivated static vessel, with the free radical inhibitor toluene always present, is homogeneous, unimolecular and follows a first‐order rate law. The rate coefficient is expressed by the following Arrhenius equations: Phenyl chloroformate: Formation of chlorobenzene, log kI = (14.85 ± 0.38) – (260.4 ± 5.4) kJ mol?1 (2.303RT)?1; r = 0.9993 Formation of 2‐chlorophenol, log kII = (12.76 ± 0.40) – (237.4 ± 5.6) kJ mol?1(2.303RT)?1; r = 0.9993 p‐Tolyl chloroformate: Formation of p‐chlorotoluene: log kI = (14.35 ± 0.28) – (252.0 ± 1.5) kJ mol–1 (2.303RT)?1; r = 0.9993 Formation of 2‐chloro‐4‐methylphenol, log kII = (12.81 ± 0.16) – (222.2 ± 0.9) kJ mol?1(2.303RT)–1; r = 0.9995 The estimation of the kI values, which is the decarboxylation process in both substrates, suggests a mechanism involving an intramolecular nucleophilic displacement of the chlorine atom through a semipolar, concerted four‐membered cyclic transition state structure; whereas the kII values, the decarbonylation in both substrates, imply an unusual migration of the chlorine atom to the aromatic ring through a semipolar, concerted five‐membered cyclic transition state type of mechanism. The bond polarization of the C–Cl, in the sense Cδ+ … Clδ?, appears to be the rate‐determining step of these elimination reactions. 相似文献
36.
Electromagnetically induced absorption (EIA) was observed for the first time on a sample of 85Rb in a magneto-optical trap using low intensity cw copropagating pump and probe optical fields. Narrow resonances revealing the dependence of the ground-state Zeeman sublevels energy structure on the quadrupolar magnetic field and the trapping optical field intensity at different trap positions, were observed. Coherence resonances as narrow as 30 kHz were obtained under low trapping field intensities. The use of EIA spectroscopy for the magnetic field mapping of cold atomic samples is illustrated. 相似文献
37.
Oier Pajuelo-Corral Andoni Zabala-Lekuona Dr. Eider San Sebastian Dr. Antonio Rodríguez-Diéguez Dr. Jose Angel García Dr. Luis Lezama Prof. Enrique Colacio Dr. Jose M. Seco Dr. Javier Cepeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(59):13484-13498
Herein, the synthesis and study of bifunctional coordination polymers (CPs) with both magnetic and photoluminescence properties, derived from a heterometallic environment, are reported. As a starting point, three isostructural monometallic CPs with the formula [M(μ-2ani)2]n (MII=Mn ( 1Mn ), Co ( 3Co ) and Ni ( 4Ni ); 2ani=2-aminonicotinate), crystallise as chiral 2D-layered structures stacked by means of supramolecular interactions. These compounds show high thermal stability in the solid state (above 350 °C), despite which, in aqueous solution, compound 1Mn is shown to partially transform into a novel 1D chain CP with the formula [Mn(2ani)2(μ-H2O)2]n ( 2Mn ). A study of the direct current (dc) magnetic properties of 1Mn , 3Co and 4Ni reveals a spin-canted structure derived from antisymmetric antiferromagnetic weak exchanges along the chiral network (as confirmed by DFT calculations) and magnetic anisotropy of the ions, in such a way that long-range ordering is observed with variable magnitude for the spin carriers. Moreover, compounds 3Co and 4Ni show no frequency-dependent alternating current (ac) susceptibility curves under zero dc field; this is characteristic behaviour of a glassy state that may be partially supressed for 3Co by applying an external dc field. To overcome long-range magnetic ordering, CoII ions are diluted in a diamagnetic ZnII-based matrix, which enables single-molecule magnet behaviour. Interestingly, this strategy allows a bifunctional CoxZn1−x2ani material, which is imbued with a strong photoluminescent emitting capacity, as characterised by an intense blue light followed by a green afterglow, to be obtained. 相似文献
38.
Caballero AB Rodríguez-Diéguez A Vidal I Dobado JA Castillo Ó Lezama L Salas JM 《Dalton transactions (Cambridge, England : 2003)》2012,41(6):1755-1764
Conventional reactions of the new multidentate ligand 7-amine-1,2,4-triazolo[1,5-a]pyrimidine (7atp, 1) with copper(II) salts lead to four novel multidimensional coordination complexes [Cu(7atp)(mal)(H(2)O)(2)]·H(2)O (2), [Cu(2)(μ-7atp)(4)(H(2)O)(2)](ClO(4))(4)·3H(2)O (3), {[Cu(7atp)(2)(μ-ox)]·3H(2)O}(n) (4) and {[Cu(7atp)(2)(μ-suc)]·2H(2)O}(n) (5), where ox(2-), mal(2-) and suc(2-) mean oxalate, malonate and succinate, respectively. In these compounds, the 7atp ligand coordinates monodentately through its atom N3, except for compound 3, which displays N3-N4 coordination mode, giving rise to all to structures with diverse topologies and dimensionality. Compound 2 is a mononuclear entity, 3 consists of dinuclear species, 4 is a zig-zag chain with oxalate as a bridging ligand and 5 is a succinate-bridged mono-dimensional system. All polynuclear metal complexes show antiferromagnetic interactions of with J values ranging from -0.12 to -49.5 cm(-1). The ligand donor capabilities have been estimated by topological analyses of the electron density (QTAIM) and electron localization function (ELF), obtained by DFT calculations. The compounds are the first structurally characterized copper(II) complexes containing the 7atp ligand. 相似文献
39.
San Felices L Vitoria P Gutiérrez-Zorrilla JM Lezama L Reinoso S 《Inorganic chemistry》2006,45(19):7748-7757
Four hybrid inorganic-metalorganic compounds containing copper(II)-monosubstituted Keggin polyoxotungstates, K3[Cu(I)(4,4'-bpy)]3[SiW11Cu(II)O39].11H2O (1), (paraquat)3[SiW11Cu(II)O39].6H2O (2; paraquat = N,N'-dimethyl-4,4'-bipyridinium), K3[Cu(I)(4,4'-bpy)]3[GeW11Cu(II)O39].11H2O (3), and Na2[Cu(I)(4,4'-bpy)]3[PW11Cu(II)O39(H2O)].4H2O (4), have been synthesized under autogenous pressure hydrothermal conditions and characterized by elemental analysis and infrared spectroscopy (FT-IR). The crystal structures of 1, 2, and 4 have been established by single-crystal X-ray diffraction. The crystal packings are characterized by the presence of monodimensional extended entities: either the polymeric polyanion [SiW11CuO39]n(6n-) (2), the cationic [Cu(4,4'-bpy)]n(n+) chain (4), or both simultaneously as in compound 1, where the inorganic and metalorganic sublattices are mutually perpendicular. To asses the influence of packing in the copper(I) complex structural diversity found in compounds 1 and 4, a search in the CSD database has been performed and the resulting geometrical features have been analyzed and compared with experimental crystallographic data and DFT calculations. 相似文献
40.
Lozano AA Sáez M Pérez J García L Lezama L Rojo T López G García G Santana MD 《Dalton transactions (Cambridge, England : 2003)》2006,(32):3906-3911
CO2 and HCO3- react with the dinuclear hydroxo-complex [Ni(mcN3)(mu-OH)]2(PF6)2 (mcN3 = 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene) to form micro-CO3 bridged nickel(II) complexes, [{Ni(mcN3)}2(mu-CO3)](PF6)2 (1a) with a symmetric core in which both nickel atoms are five-coordinate and [Ni(mcN3)(mu-CO3)Ni(mcN3)(MeCN)](PF6)2 (1b) with an asymmetric dinuclear core containing five- and six-coordinate nickel atoms. The magnetic behaviour indicates the existence of antiferromagnetic coupling between the metallic centres. A substantial increase in the value of J occurs when the symmetric five-coordinate nickel species transforms to an asymmetric five- and six-coordinate species by axial coordination of acetonitrile. 相似文献