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991.
Chandan Adhikary Jean-Pierre Tuchagues Sandra Ianelli Subratanath Koner 《Inorganica chimica acta》2009,362(15):5211-5218
Two mixed-ligand copper(II) complexes [{Cu(L1)(μ1,3-N3)}{Cu(L)(μ1,3-N3)(μ1,1-N3)}]n (1) [HL1 = 1-(N-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane; L = 2-(dimethylamino)-ethylamine] and [{Cu(L2)(μ1,3-N3)}{Cu(L)(μ1,3-N3)(μ1,1-N3)}]n (2) [HL2 = 1-(N-5-methoxy-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane] have been formed upon addition of aqueous solution of sodium azide to a methanolic solution of copper nitrate trihydrate and corresponding Schiff-base ligands. The ligands, HL1 and HL2 undergo partial hydrolysis of their imine bond during the course of reaction. Both the complexes contain single end-to-end (μ1,3) azido bridged 1D infinite chains (rail) which propagate parallel to the crystallographic b-axis; neighboring chains are interconnected by pairs through double asymmetric end-on (μ1,1) azido bridges (rung) to yield a ladder-like structure. In both complexes, rungs (end-on azido bridges) do not connect copper centers of the chains like in a regular ladder; instead they connect only the alternating copper sites of the 1D chain. In a chain the coordination environment around copper(II) ions are not the same: while the {Cu(L1)(μ1,3-N3)} and {Cu(L2)(μ1,3-N3)} moieties have a penta-coordinated copper(II) center, the copper(II) ion of the neighboring {Cu(L1)(μ1,3-N3)(μ1,1-N3)} or {Cu(L2)(μ1,3-N3)(μ1,1-N3)} moiety has an octahedral coordination environment. The variable temperature (2-300 K) magnetic susceptibility measurements showed that the magnetic interaction between the metal centers in complexes 1 and 2 is dominantly antiferromagnetic. The results of magnetic model are in good agreement with the experimental data. 相似文献
992.
Tanmay K. Jana Rabindranath Pradhan Subhajit Dinda Corine Simonnet Inhar Imaz Léopold Fournès Francis Sécheresse Ramgopal Bhattacharyya 《Inorganica chimica acta》2009,362(10):3583-3594
Iron (II) and iron (III) complexes, [FeII(DEDTC)2(dppe)] · CH2Cl2 (1), [FeII(ETXANT)2(dppe)] (2) (DEDTC = diethyldithiocarbamate, ETXANT = ethyl xanthate, dppe = 1,2-bis (diphenylphosphino) ethane), and [FeIII(DEDTC)2(dppe)] [FeIIICl4] (3) have been synthesized and characterized. Since 3 contains two magnetic centers, an anion metathesis reaction has been conducted to replace the tetrahedral FeCl4− by a non-magnetic BPh4− ion producing [FeIII(DEDTC)2(dppe)]BPh4 (4) for the sake of unequivocal understanding of the magnetic behavior of the cation of 3. With the similar end in view, the well-known FeCl4− ion, the counter anion of 3, is trapped as PPh4[FeIIICl4] (5) and its magnetic property from 298 to 2 K has been studied. Besides the spectroscopic (IR, UV-Vis, NMR, EPR, Mass and XPS) characterization of the appropriate compounds, especially 2, others viz. 1, 3 and 4 have been structurally characterized by X-ray crystallography. While FeII complexes, 1 and 2, are diamagnetic, the FeIII systems, namely the cations of 3, and 4 behave as low-spin (S = 1/2) paramagnetic species from 298 to 50 K. Below 50 K 3 shows gradual increase of χMT up to 2 K suggesting ferromagnetic behavior while 4 exhibits gradual decrease of magnetic moment from 60 to 2 K, indicating the occurrence of weak antiferromagnetic interaction. These conclusions are supported by the Mössbauer studies of 3 and 4. The Mössbauer pattern of 1 exhibits a doublet site for diamagnetic (2-400 K) FeII. The compounds 1, 2 and 4 encompass interesting cyclic voltammetric responses involving FeII, FeIII and FeIV. 相似文献
993.
A new route to {Cu2(κ1-pyNH2)2(μ-OMe)2Cl2}n (pyNH2 = 2-aminopyridine) (3) is reported. Structural characterisation reveals the presence of methoxide and chloride bridging units within the complex which support close copper-copper bonding interactions resulting in interesting magnetic properties. The variable-temperature (4-300 K) magnetic susceptibility data of the complex were interpreted with the dimer law using the molecular field approximation. The results obtained indicate a weak antiferromagnetic (zJ′ = −15 cm−1) inter-chain interaction through the chloro-bridge. A relatively strong antiferromagnetic interaction, transmitted through the oxygen-bridge, with an exchange coupling of 2J = −305 cm−1, which dominates the magnetic properties of the title complex. 相似文献
994.
Wen-Tong Chen Shao-Ming Ying Dong-Sheng Liu Qiu-Yan Luo Ya-Ping Xu 《Inorganica chimica acta》2009,362(7):2379-819
Two 3d/5d-4f metal complexes [DyL3(H2O)2]n(1.5nHgCl4) · 2nH2O (1) and (1.5nZnCl4) · nH2O (2), where L and L′ are isonicotinic acid and nicotinic acid, respectively, have been synthesized via hydrothermal reaction and structurally characterized by single-crystal X-ray diffractions. Both complexes are characteristic of a one-dimensional polycationic chain-like structure. Photoluminescent investigation reveals that complex 1 displays emissions in violet, blue and yellow regions, and the violet emission is stronger than the blue and yellow ones. Complex 2 displays emissions in orange and red regions, and the emission are attributed to the characteristic emissions of 5D0 → 7FJ (J = 0, 1, 2, 3, 4) of Eu3+ ions. Optical absorption spectra reveal the presence of an optical gap of 3.31 and 3.86 eV for 1 and 2, respectively. The magnetic properties show that complex 1 exhibits antiferromagnetic-like interactions. 相似文献
995.
Using new nitronyl nitroxide radical ligand 2-[4-(1-imidazole)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NITPhIm), three new complexes [M(hfac)2(NITPhIm)]2 (M = Cu(II) 1, Mn(II) 2, Co(II) 3; hfac = hexafluoroacetylacetonate) have been prepared. Three complexes possess cyclic dimer structure in which each NITPhIm radical links two different metal ions through the oxygen of nitroxide group and the nitrogen of imidazole. The magnetic studies show the copper(II) ion interacts ferromagnetically with the directly bonding nitronyl nitroxide while manganese(II) and cobalt(II) ions strong antiferromagnetically interact with the directly coordinated nitroxide groups. There is a weak antiferromagnetic coupling between the metal ion and the nitroxide through phenyl and imidazole rings of the radical ligand, which is agreement with spin polarization mechanism. The results show that the minor changes in the structure of radical ligand can change the magnetic behavior of radical-metal complex. 相似文献
996.
Three new lanthanide coordination polymers based on mixed acid ligands [Ln(oba)(ox)0.5(H2O)2]n (Ln = Y (1); Er (2); Yb (3). H2oba = 4,4′-oxybis (benzoic acid); H2ox = oxalic acid) were prepared by hydrothermal reactions and characterized by single-crystal X-ray diffraction. In these complexes, lanthanide ions are bridged by oba ligands to form 1D double-stranded chains, which are further connected by ox ligands, resulting in the formation of 2D (4,4) grids. The upconversion emission of the Y:Er-Yb co-doped coordination polymer was studied and the unusual blue emission for the Er(III) complexes was observed, which arises from the 2H9/2 → 4I15/2 transition and can be explained by three-photon excitation mechanism which is mostly phonon-dependent. The introduction of the oxalate anion without high-energy vibrational groups is beneficial to the increasing intensity of upconversion fluorescence. The magnetic properties of complexes 2 and 3 were investigated. The decrease of χMT over the temperature range of 300-2 K and the negative value of θ are due primarily to the splitting of the ligand field of the ErIII and YbIII ions together with the possible weak antiferromagnetic coupling between the rare earth ions. 相似文献
997.
Two new Mn(II) coordination polymers with bis(5-tetrazolyl)methane (H2btm), [Mn(btm)(phen)(H2O)] · H2O (1) and [Mn(btm)(2,2′-bpy)] · 1.5H2O (2), have been synthesized and their structures determined by X-ray diffraction. In complex 1, the btm ligands assume the μ2-1,1′:4 coordination mode and interlink Mn(II) ions into infinite one-dimensional chains. The chains are assembled into a three-dimensional architecture via hydrogen bonds and π-π interactions. For 2, Mn(II) ions are connected by btm ligands in the μ3-1,1′:2:3′ mode to produce two-dimensional (6,3) coordination network. Magnetic investigations revealed that interactions through the btm bridges in both 1 and 2 are antiferromagnetic. 相似文献
998.
A novel series of linear chain coordination polymers, [NH4][MII(H2PO2)3(H2O)] where M = Mn, Co, Ni, has been obtained by the reaction of divalent metals salts with ammonium pyrophosphite, [NH4][H2PO2], in a methanol-water mixture. They crystallise in the monoclinic P21/n cell and contain polar chains aligned with opposing polarity. Both bridging and terminal monodentate coordination modes are exhibited by the . Two types of hydrogen-bond between a coordinated water and a monodentate connect the chains into a 3D-network. The compounds have been further characterised by IR and UV-Vis spectroscopies, TGA, and their magnetic properties measured. All three compounds exhibit weak antiferromagnetic nearest neighbour interaction. A similar study on the known [FeIII(H2PO2)3] is also reported. Its magnetic susceptibility fits a model for a 1D-antiferromagnet with 2 J/k of 1.20(1) K and g of 2.019(2). 相似文献
999.
Alexander F. Shestakov Yuri M. Shul’ga Nataliya A. Sanina Sergei M. Aldoshin Victor I. Ovcharenko 《Inorganica chimica acta》2009,362(7):2499-8289
Geometrical and electronic structures of neutral paramagnetic binuclear nitrosyl iron complexes with azaheterocyclic thyolyls [Fe2(μ-SR)2)(NO)4] with bridging ligands: aminomercaptotriazolyl, RC2N3H(NH2) (1), mercaptoimidazolyl, RC3N2H3 (2), methylmercaptoimidazolyl, RC3N2H2CH3 (3), and dihydromercaptoimidazolyl, RC3N2H5 (4) have been calculated by the methods of density functional, B3LYP and PBE. Coordination of bridging ligands corresponds to ‘S-C-N type’, more energetically preferable than μ-S type coordination. This results in big Fe?Fe distances, with the value of intramolecular exchange interaction being inconsiderable; therefore the complexes are paramagnetic at ambient temperature, with effective magnetic moment about 2.5 Bohr magneton. The interaction of the Fe atoms spins and intermolecular exchange are antiferromagnetic, and this should be taken into account while describing the temperature dependence of magnetic susceptibility. The electronic configuration of the Fe(NO)2 unit with one unpaired electron (similar to that in binuclear diamagnetic complexes) forms due to binding of spin 3/2 of Fe+d7 center with oppositely oriented spins 1/2 of two NO groups. Theoretical approaches describe satisfactorily not only the experimental structure of the complexes but also their IR spectra. 相似文献
1000.
New examples of low-dimensional metal-pydco complexes: Syntheses, structures and magnetic properties
This work presents a systematic investigation on coordination chemistry of a novel pyridine-2,6-dicarboxylic acid N-oxide (pydco), and also reveals the significant function of supramolecular interactions in dominating the resultant crystalline nets. Assemblies of pydco with transition-metal ions under similar conditions yield a series of polymers in the absence/presence of the organonitrogen ligands {[Cu(pydco)(L)0.5(H2O)] · 2H2O}n (L = bipy (1), bpa (2) and bpe (3)), {[M(pydco)(bpp)(H2O)] · 2H2O}n (M = Cu (4) and Ni (5)), [Ag2(pydco)]n (6) and [Ag2Cu(pydco)2]n (7) (bipy = 4,4′-bipyridine, bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethene, bpp = 1,3-bis(4-pyridyl)propane). 1-5 feature different structural characteristics, although they exhibit analogous chain networks. Remarkably, extended architectures are further constructed with the aid of weak interactions. Reaction of pydco with AgAc yields a 2-D polymer 6, which was reported in our recent Communication. A mixed-metal coordination polymer 7 was obtained by the self-assembly of AgAc, Cu(Ac)2 · H2O and pydco.In 7, two left- and right-hand helical chains are constructed by carboxylic groups of pydco and Cu centers, which are further connected by [AgCO2]2 cores into a 2-D network. Structural evolution under the co-ligand intervention in this series of compounds, as well as the general coordination rule of pydco, has been further discussed. Furthermore, variable temperature magnetic properties of 1, 3 and 7 are also studied. The magnetic measurements of 1 and 3 reveal the existence of weak antiferromagnetic interactions with J1 = −4.59 cm−1 and J2 = −4.63 cm−1, respectively. Whereas 7 displays weak ferromagnetic interactions with J3 = 1.81 cm−1. 相似文献