Synthesis and crystal structure of a cis-oxime-oximate bridged tetra coordinated open-book shaped new dicopper(II/II) complex [Cu2(μ-Hdmg)2(Hdmg)]ClO4: First report of unusual oxime OH bridging (original) (raw)
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Inorganica Chimica Acta, 2011
A new tetranuclear complex, [Cu 4 L 4 ](ClO 4 ) 4 Á2H 2 O (1), has been synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligand (2E,3E)-3-(2-aminopropylimino) butan-2-one oxime (HL). Single-crystal X-ray diffraction studies reveal that complex 1 consists of a Cu 4 (NO) 4 core where the four copper(II) centers having square pyramidal environment are arranged in a distorted tetrahedral geometry. They are linked together by a rare bridging mode (l 3 -g 1 ,g 2 ,g 1 ) of oximato ligands. Analysis of magnetic susceptibility data indicates moderate antiferromagnetic (J 1 = À48 cm À1 , J 2 = À40 cm À1 and J 3 = À52 cm À1 ) exchange interaction through r-superexchange pathways (in-plane bridging) of the oxime group. Theoretical calculations based on DFT technique have been used to obtain the energy states of different spin configurations and estimate the coupling constants and to understand the exact magnetic exchange pathways.
Journal of The Chemical Society-dalton Transactions, 1999
The tetranuclear complex [Cu 4 (L) 4 (H 2 O) 8 ][ClO 4 ] 4 ؒ2H 2 O (HL = 1,3-dimethylvioluric acid, i.e. 1,3-dimethyl-5-(hydroxyimino)-2,4,6(1H,3H,5H)-pyrimidinetrione) has been prepared and its crystal structure determined by X-ray diffraction methods. The structure consists of a tetranuclear cation [Cu 4 (L) 4 (H 2 O) 8 ] 4ϩ , four non-co-ordinated perchlorate anions and two water molecules located on a 4-fold rotation-inversion axis. Within each cation the four copper() ions, linked through four bis(bidentate) L Ϫ ligands, are arranged at the vertices of a strict square-planar parallelogram with edge and diagonal Cu ؒ ؒ ؒ Cu distances of 4.764(3) and 6.738(4) Å, respectively. Each oxime group acts as a bridge between adjacent copper ions with an anti conformation and each copper is co-ordinated by two L Ϫ ligands. The copper atoms exhibit a CuO 5 N elongated distorted octahedral co-ordination environment, with three oxygen atoms and one nitrogen atom of the L Ϫ ligands at equatorial positions and the water oxygens at axial positions. From variable-temperature magnetic susceptibility measurements the compound was found to exhibit a very strong antiferromagnetic exchange interaction through the oximate bridges with J = Ϫ349 cm Ϫ1 [ϪJ(S Cu ؒS CuA ϩ S CuA ؒS CuC ϩ S CuC ؒS CuB ϩ S CuB ؒS Cu )], leading to complete spin coupling at 70 K.
Dalton Transactions, 2014
A set of four copper(II) complexes, L 1-X and L 2-X (X = Cl, Br; L 1 = N-(L-leucine methyl ester)-N'-((2-pyridin-2-yl)methyl)oxalamide and L 2 = N-benzyl-N'-((2-pyridin-2-yl)methyl)oxalamide), have been synthesized and characterized by X-ray structural analysis, electron paramagnetic resonance (EPR) spectroscopy on single crystals and by SQUID magnetization measurements. X-ray diffraction studies show one-dimensional hydrogen bonded networks of dimeric copper(II)-complexes bridged by two halide ions and with the two metal centers 3.44-3.69 Å apart. The geometry at each copper(II) atom is ideal or near ideal square pyramidal. EPR and SQUID studies indicate that all complexes exhibit weak antiferromagnetic interactions between the Cu(II) paramagnetic centers, with exchange parameter |J| ∼ 1 cm −1. Magneto-structural comparisons among similar dihalo-bridged Cu(II) dinuclear complexes are also provided, and a possible correlation has been established. † Electronic supplementary information (ESI) available: FT-IR spectra and XRPD data of the complexes L 1-Cl, L 1-Br, L 2-Cl and L 2-Br; Additional crystallographic information; Angular variation of g-values and the W pp linewidths of EPR lines for L 2-Cl, L 1-Br and L 2-Br; Curie-Weiss magnetization fitting curves. CCDC 919441-919443. For ESI and crystallographic data in CIF or other electronic format see
Zeitschrift für Naturforschung B, 2014
The dimeric copper(II) complex [Cu(C2O4)(H2oxado)(H2O)]2 (1), where H2oxado=oxamide dioxime, has been synthesized in water and characterized by elemental and thermal analyses, IR spectroscopy, and single-crystal X-ray diffraction. Complex 1 is composed of two neutral [Cu(C2O4)(H2oxado)(H2O)] entities connected by Cu-O bonds between oxalate oxygen atoms and copper(II) ions, thereby producing a centrosymmetric dimer, with the Cu(II) centers exhibiting a strongly distorted octahedral coordination. Neighboring dimers are hydrogen-bonded through O- H···O interactions leading overall to a layer structure. Thermal analyses of complex 1 showed two significant weight losses corresponding to the coordinated water molecules, followed by the decomposition of the network. Variable-temperature (10 - 300 K) magnetic susceptibility measurements revealed very weak antiferromagnetic interactions (θ = 0:86 K from Curie-Weiss law behavior) within the dinuclear unit
Inorganica Chimica Acta, 1993
The synthesis, crystal structure and magnetic properties are reported for the trinuclear compound [Cu(H,0),{Cu(HL)(H,0)(C104)}~][C10,],~2H,0, where HL is the monodeprotonated form of 6-methylamino-1,3dimethyl-5-[(2'-carboxyphenyl)azo]uracil. The compound crystallizes in the triclinic system, space group Pl, with cell constants a = 7.824(3), 6 = 12.278(3), c = 13.705(9) A, (Y= 104.34(3), /3=91.80(3), y= 103.37(5)" and Z= 1. The structure was solved and refined to R = 0.071 (R,=O.O64). The structure consists of trinuclear [Cu(H,O),{Cu(HL)(H,O)(CIO,)},lZ+ cations, non-coordinated perchlorate anions and crystal water molecules, held together by a network of hydrogen bonds. The central copper is in an elongated octahedral CuO, chromophore and the terminal copper atoms in distorted square-pyramtdal CuNO, chromophores. Adjacent copper atoms are linked by carboxylate groups in a syn-anti conformation. From the magnetic susceptibility measurements, the complex is found to exhibit weak ferromagnetic interaction between nearest-neighbour copper(I1) ions. The magnitude and nature of the exchange coupling are discussed on the basis of the structural data.
European Journal of Inorganic Chemistry, 2005
Four new trinuclear copper(II) complexes, [(CuL 1 ) 3 (µ 3 -OH)](ClO 4 ) 2 ·H 2 O (1), [(CuL 2 ) 3 (µ 3 -OH)](ClO 4 ) 2 (2), [(CuL 3 ) 3 -(µ 3 -OH)](ClO 4 ) 2 ·H 2 O (3), and [(CuL 4 ) 3 (µ 3 -OH)](ClO 4 ) 2 ·H 2 O (4), where HL 1 = 8-amino-4,7,7-trimethyl-5-azaoct-3-en-2one, HL 2 = 7-amino-4-methyl-5-azaoct-3-en-2-one, HL 3 = 7-(ethylamino)-4-methyl-5-azahept-3-en-2-one, and HL 4 = 4methyl-7-(methylamino)-5-azahept-3-en-2-one, have been derived from the four tridentate Schiff bases (HL 1 , HL 2 , HL 3 , and HL 4 ) and structurally characterized by X-ray crystallography. For all compounds, the cationic part is trinuclear with a Cu 3 OH core held by three carbonyl oxygen bridges between each pair of copper(II) atoms. The copper atoms are five-coordinate with a distorted square-pyramidal geometry; the equatorial plane consists of the bridging oxygen atom of the central OH group together with three atoms (N, N, O) from one ligand whereas an oxygen atom of a second ligand [a]
Inorganic Chemistry Communications, 2004
This paper reports the synthesis and complete characterization (structural, spectroscopic and magnetic) of [Cu(HBI-MAM)Cl(C 4 O 4)] n AE (H 2 O) n [BIMAM = bis(imidazol-2-yl)methylaminomethane]. This compound is made of infinite chains-running along c axis-built from [CuCl(HBIMAM)] + units bridged together by l-O 1 ,O 3-bis(monodentate) squarate anions. Non-covalent interactions (H-bonds and p-p) drive the build-up of an infinite three-dimensional array. The coordination polyhedron about the copper(II) ion is distorted square pyramidal. The EPR spectrum is indicative of a d z 2 Ày 2 ground state for the Cu(II) ions with significant contribution of d z 2. Magnetic susceptibility measurements in the range 1.8-200 K show weak antiferromagnetic exchange interactions (2J = À3.5(1) cm À1). The observed magnetic behaviour is discussed in terms of the crystal structure and compared with that observed in related copper(II) complexes containing l-O 1 ,O 3-squarato bridges.