Octanuclearity in Copper(II) Chemistry: Preparation, Characterization, and Magnetochemistry of [Cu8(dpk·OH)8(O2CCH3)4](ClO4)
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- 作者：Vasilis Tangoulis ; Catherine P. Raptopoulou ; Aris Terzis ; Sofia Paschalidou ; Spyros P. Perlepes ; and Evangelos G. Bakalbassis
- 刊名：Inorganic Chemistry
- 出版年：1997
- 出版时间：August 27, 1997
- 年：1997
- 卷：36
- 期：18
- 页码：3996 - 4006
- 全文大小：448K
- 年卷期：v.36,no.18(August 27, 1997)
- ISSN：1520-510X
文摘
The complexes[Cu8(dpk·OH)8(O2CMe)4](ClO4)4·9H2O(1) and[Cu(dpk·H2O)2](O2CMe)(ClO4)·2H2O(2), wheredpk·H2O is the hydrated, gem-diol form ofdi-2-pyridyl ketone, have been prepared. Complex 1crystallizes intriclinic space group P
with the following unit celldimensions at 25 
C: a = 18.396(1) Å, b= 16.720(1) Å,c = 19.171(1) Å, 
= 96.10(1), 
=87.68(1), 
= 99.14(1), Z = 2.Crystal structure data for 2 at roomtemperature are as follows: monoclinic,P21/c, a =13.000(2) Å, b = 8.008(1) Å, c =27.095(3) Å, = 93.19(1), Z = 4. The two centrosymmetrically relatedcubanes in the tetracation of 1 are doubly-bridged withtwosyn, anti acetate groups bridging twoCuII atoms. The monoanion dpk·OH-functions as a
1:3:1:
3ligand.Three CuII atoms have distorted octahedralcoordination geometries with CuO3N3 andCuNO5 chromophores,while the fourth CuII center displays a distorted squarepyramidal geometry; a terminal monodentate acetate isligated to this latter CuII atom. In the mononuclear[Cu(dpk·H2O)2]2+ cationof 2, the four pyridyl nitrogens canbe viewed as strongly coordinating to the metal (Cu-N =2.013(4)-2.022(4) Å), while one of thehydroxyloxygens on each ligand forms a weak bond to CuII (Cu-O= 2.417(4), 2.352(3) Å). Variable-temperaturemagneticsusceptibility studies on 1 are in line with both an overallantiferromagnetic interaction between CuII atomsandthe magnetic behavior of a simple cubane. Exchange parameters,J, derived by using a four-J magneticmodel,are found to be J1 = 6cm-1, J2 = -144cm-1, J3 = -14cm-1, J4 = 3cm-1 and g = 2.29 (adjustableparameter)by least-squares fitting to the spin Hamiltonian H =-2
i<jJijSi·Sj.The thus derived energy level spectrumshows a S = 1 ground state, further supported by thesolid-state and solution EPR spectra of 1. Insightconcerningthe effect of structural parameters on the magnitude of the magneticexchange interactions was gained throughEHMO calculations performed on a model Cu(OR)2Cumoiety. Accordingly, estimates of the Jparameters,experimentally derived, were in close agreement both with knownmagneto-structural correlations establishedfor planar Cu(OR)2Cu moieties and a criterionestablished by us, holding for the magneto-structuralcorrelationsin symmetrical roof-shaped, alkoxo-bridged Cu(OR)2Cumoieties.
with the following unit celldimensions at 25 C: a = 18.396(1) Å, b= 16.720(1) Å,c = 19.171(1) Å, = 96.10(1), =87.68(1), = 99.14(1), Z = 2.Crystal structure data for 2 at roomtemperature are as follows: monoclinic,P21/c, a =13.000(2) Å, b = 8.008(1) Å, c =27.095(3) Å, = 93.19(1), Z = 4. The two centrosymmetrically relatedcubanes in the tetracation of 1 are doubly-bridged withtwosyn, anti acetate groups bridging twoCuII atoms. The monoanion dpk·OH-functions as a1:3:1:3ligand.Three CuII atoms have distorted octahedralcoordination geometries with CuO3N3 andCuNO5 chromophores,while the fourth CuII center displays a distorted squarepyramidal geometry; a terminal monodentate acetate isligated to this latter CuII atom. In the mononuclear[Cu(dpk·H2O)2]2+ cationof 2, the four pyridyl nitrogens canbe viewed as strongly coordinating to the metal (Cu-N =2.013(4)-2.022(4) Å), while one of thehydroxyloxygens on each ligand forms a weak bond to CuII (Cu-O= 2.417(4), 2.352(3) Å). Variable-temperaturemagneticsusceptibility studies on 1 are in line with both an overallantiferromagnetic interaction between CuII atomsandthe magnetic behavior of a simple cubane. Exchange parameters,J, derived by using a four-J magneticmodel,are found to be J1 = 6cm-1, J2 = -144cm-1, J3 = -14cm-1, J4 = 3cm-1 and g = 2.29 (adjustableparameter)by least-squares fitting to the spin Hamiltonian H =-2i<jJijSi·Sj.The thus derived energy level spectrumshows a S = 1 ground state, further supported by thesolid-state and solution EPR spectra of 1. Insightconcerningthe effect of structural parameters on the magnitude of the magneticexchange interactions was gained throughEHMO calculations performed on a model Cu(OR)2Cumoiety. Accordingly, estimates of the Jparameters,experimentally derived, were in close agreement both with knownmagneto-structural correlations establishedfor planar Cu(OR)2Cu moieties and a criterionestablished by us, holding for the magneto-structuralcorrelationsin symmetrical roof-shaped, alkoxo-bridged Cu(OR)2Cumoieties.