The synthesis of five new Cu(II) compounds of formula [Cu(HBIP)(C(2)O(4))].H(2)O (1), [Cu(HBIP)(C(2)O(4))(OH(2))].2H(2)O (2), [{Cu(HBIP)Cl}(2)(&mgr;-C(2)O(4))].2H(2)O (3), [{Cu(BIP)}(2)(&mgr;-C(2)O(4))].2H(2)O (4) and [{Cu(BIP)}(2)(&mgr;-C(2)O(4))].6H(2)O (5), together with their spectral and magnetic characterization, is reported. Crystal structures of compounds 2, 3 and 5 have been solved. All these compounds crystallize in the triclinic system, space group P&onemacr;, with a = 7.3322(3) Å, b = 10.014(1) Å, c = 11.541(1) Å, alpha = 113.22(1) degrees, beta = 91.37(1) degrees, gamma = 94.51(1) degrees, Z = 2 for compound 2; a = 7.444(2) Å, b = 8.518(2) Å, c = 11.231(2) Å, alpha = 97.45(2) degrees, beta = 98.99(2) degrees, gamma = 97.95(2) degrees, Z = 1 for compound 3; and a = 7.977(1) Å, b = 8.656(1) Å, c = 11.807(1) Å, alpha = 69.06(1) degrees, beta = 86.07(1) degrees, gamma = 67.36(1) degrees, Z = 1 for compound 5. In compound 2 the asymmetric unit consists of one isolated neutral [Cu(HBIP)(C(2)O(4))(OH(2))] molecule and two noncoordinated water molecules. The Cu(II) ion is five-coordinated (4+1 coordination mode) with HBIP and oxalato entities acting as bidentate ligands and the water molecule as the fifth ligand. The structure of compound 3 is made up of centrosymmetric binuclear [{Cu(HBIP)(Cl)}(2)(&mgr;-C(2)O(4))] units and noncoordinated water molecules. The two copper atoms are linked through a bis-bidentate oxalato group leading to a metal-metal separation of 5.28(3) Å. The coordination stereochemistry of the CuN(2)O(2)Cl chromophore is approximately SP. Compound 5 exhibits a structure built of ladder-like chains. In these chains the rungs are constituted by the neutral dinuclear centrosymmetric [(BIP)Cu(C(2)O(4))Cu(BIP)] entities. The oxalato group bridges two copper atoms in a bis-bidentate fashion, whereas the BIP acts as a tridentate ligand, connecting through their carboxylate groups these dimeric units along the a axis. The copper atom is involved in a five-coordinated CuN(2)O(2)O' chromophore, with a coordination geometry intermediate between SP and TBP. The magnetic properties of all complexes have been investigated. Compound 1 and 2 follow a Curie-Weiss law with very low values of theta. The other three compounds exhibit an antiferromagnetic coupling, with 2J = -265 cm(-)(1) for 3, 2J = -108 cm(-)(1) for 4, and 2J = -5.7 cm(-)(1) for 5. The strength of the exchange interaction is discussed on the basis of the structural features and correlated with published magneto-structural data on similar oxalato-bridged copper(II) compounds.

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Two polynuclear copper(II)-squarate compounds of formulas [Cu(HBIP)(BIP)](C(4)O(4))(1/2).2H(2)O (1) and [[Cu(BIP)(OH(2))](4)(mu-C(4)O(4))](ClO(4))(2).4H(2)O (2) (HBIP = 3,3-bis(2-imidazolyl)propionic acid) have been synthesized and characterized by single-crystal X-ray diffraction. Both compounds crystallize in the triclinic system, space group P1, with a =7.947(1) A, b =12.327(4) A, c = 13.150(3) A, alpha = 113.91(2) degrees, beta = 99.85(2) degrees, gamma = 90.02(2) degrees for compound 1 and a = 8.010(1) A, b = 13.073(1) A, c = 14.561(1) A, alpha = 72.13(1) degrees, beta = 80.14(1) degrees, gamma = 84.02(1) degrees for compound 2. The structure of compound 1 can be viewed as made up of [Cu(HBIP)(BIP)] units linked together by the BIP carboxylate groups to form a one-dimensional chain structure along the a axis in the crystal. The copper ion is five-coordinated (CuN(4)O chromophore) with BIP and HBIP acting as tridentate and bidentate ligands, respectively. The coordination geometry is intermediate between SP and TBP. The structure of compound 2 is made of infinite chains built from cationic tetranuclear [[Cu(BIP)(OH(2))](4)(mu-C(4)O(4))](2+) complex units, two uncoordinated perchlorate anions, and four water molecules of crystallization. The squarato group bridges the copper(II) ions, while BIP acts as a tridentate ligand, connecting through its carboxylate group the tetrameric units along the a axis. The two crystallographically independent copper(II) ions are pentacoordinated within a distorted square-based pyramid. Electronic and EPR spectra are consistent with the crystallographic data. Both compounds follow a Curie-Weiss law with very low values of theta (-0.13 and +0.12 K). In compound 2, the weak ferromagnetism interaction is discussed on the basis of the structural features and correlated with published magnetostructural data on similar squarato-bridged copper(II) compounds.

A novel mu-pyrazolato-mu-hydroxo-dibridged copper(II) complex has been synthesized and structurally characterized: [(Cu(mepirizole)Br)2(mu-OH)(mu-pz)] (mepirizole=4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine; pz=pyrazolate). The title compound crystallizes in the monoclinic system, space group P2(1)/c, with a=15.618(2) A, b=15.369(3) A, c=16.071(3) A, and beta=112.250(1) degrees. The structure is built up of dinuclear [(Cu(mepirizole)Br)2(mu-OH)(mu-pz)] units with five-coordinated copper(II) ions (CuBrN3O chromophores) linked by mu2-OH and mu2-pyrazolato bridges that are well separated from each others. The intramolecular copper-copper distance is 3.378(3) A. Magnetic susceptibility data show that the copper atoms are strongly antiferromagnetically coupled with J=-770 cm(-1). The obtained triplet-singlet energy gap is compared with those reported for a series of related dimers. The strong antiferromagnetic coupling arising from the complementarity of the hydroxo and pyrazolato bridges has been discussed on the basis of DFT calculations.