The complexes [Cu8(dpk·OH)8(O2CMe)4](ClO4)4·9H2O (1) and [Cu(dpk·H2O)2](O2CMe)(ClO4)·2H2O (2), where dpk·H2O is the hydrated, gem-diol form of di-2-pyridyl ketone, have been prepared. Complex 1 crystallizes in triclinic space group P1̄ with the following unit cell dimensions at 25 °C: a = 18.396(1) Å, b = 16.720(1) Å, c = 19.171(1) Å, α = 96.10(1)°, β = 87.68(1)°, γ = 99.14(1)°, Z = 2. Crystal structure data for 2 at room temperature are as follows: monoclinic, P21/c, a = 13.000(2) Å, b = 8.008(1) Å, c = 27.095(3) Å, β = 93.19(1)°, Z = 4. The two centrosymmetrically related cubanes in the tetracation of 1 are doubly-bridged with two syn, anti acetate groups bridging two CuII atoms. The monoanion dpk·OH- functions as a η1:η3:η1:μ3 ligand. Three CuII atoms have distorted octahedral coordination geometries with CuO3N3 and CuNO5 chromophores, while the fourth CuII center displays a distorted square pyramidal geometry; a terminal monodentate acetate is ligated to this latter CuII atom. In the mononuclear [Cu(dpk·H2O)2]2+ cation of 2, the four pyridyl nitrogens can be viewed as strongly coordinating to the metal (Cu−N = 2.013(4)−2.022(4) Å), while one of the hydroxyl oxygens on each ligand forms a weak bond to CuII (Cu−O = 2.417(4), 2.352(3) Å). Variable-temperature magnetic susceptibility studies on 1 are in line with both an overall antiferromagnetic interaction between CuII atoms and the magnetic behavior of a simple cubane. Exchange parameters, J, derived by using a four-J magnetic model, are found to be J1 = 6 cm-1, J2 = −144 cm-1, J3 = −14 cm-1, J4 = 3 cm-1 and g = 2.29 (adjustable parameter) by least-squares fitting to the spin Hamiltonian H = −2∑i

Eine Sessel‐im‐Sessel‐Anordnung der zwölf Kupferionen (unten links) kennzeichnet den einen der hier vorgestellten Kupferkomplexe, zwei über ein CuII‐Zentrum verbundene Tetraeder (unten rechts) den zweiten. Beide wurden aus MeCN‐Lösungen isoliert, die [Cu2(MeCO2)4(H2O)2] und (py)2CO enthielten. Durch Suszeptibilitätsmessungen konnte gezeigt werden, daß der siebenkernige Komplex einen Grundzustand mit S = 1/2 hat.magnified image

Treatment of [Cu-2(O2CCH3)(4)(H2O)(2)] with 2 equiv of di-2-pyridyl ketone (dpk)! in methanol followed bg addition of I equiv of NaClO4 yields [Cu-4(dpk . CH3O)(4)(CH3O)(2)](ClO4)(2) (1) in similar to 75% yield (dpk . CH3O-= the monoanion of the monomethylated diol of dpk), The same complex has also been isolated from the 1:2:2 and 1:4: 1 stoichiometries. The 1:2 reaction of Cu(ClO4). 6H(2)O with dpk in methanol affords the mononuclear complex [Cu(dpk . CH3OH)(2)](ClO4)(2) . 2CH(3)OH (2) in similar to 70% yield, Complex 1, C50H50Cl2Cu4N8O18, crystallizes in the tetragonal space group I4(i)/acd with a=b=15.551(1) Angstrom, c = 48.938(3) Angstrom and Z=8, Crystal data for 2: C26H32Cl2CuN4O14, monoclinic, space group P2(i)/a, a=12.923(1) Angstrom, b=12.969(2) Angstrom, c=9.655(1) Angstrom, beta= 92.78(1)degrees, Z=2, The four Cu-II atoms in the cation of 1 are all coplanar, exhibiting a rhombic arrangement. The dpk . CH3O- ion behaves as a eta(1):eta(2):eta(1):mu(2) ligand, In the cation of 2, the dpk . CH3OH ligand functions as a tridentate chelate toward the copper center, with the pyridyl nitrogens and the methylated oxygen being the ligated atoms. The magnetic properties of compound 1 are characteristic of prevailing antiferromagnetic interactions, The susceptibility data of 1 were fitted with a 3-J magnetic model, affording a Very strong antiferromagnetic interaction (J(2)=-490(9) cm(-1)), a weak ferromagnetic interaction (J(1)=+22(4) cm(-1), and a very weak antiferromagnetic interaction (J(3)=-0.36(1) cm(-1)), The energy spectrum of the states, the magnetization, and the EPR data of complex 1 are in line with an almost degenerate ground state with a magnetic component. An investigation of this degeneration is attempted.