| Abstract
| - Novel cyclic and linear type metal-radical clusters were obtained in a double ladder chain bridged by two nitronylnitroxide-based high-spin ligands and seven Cu(hfac)2's. Four types of copper complexes were found in these clusters having 6- and 5-fold coordination centers.
- The synthesis, X-ray crystal structure, and magnetic studies of a rare example of organic/inorganic spin hybridclusters extended in infinite ladder-type chain [Cu(C5F6HO2)2]7(C35H35N5O4)2 ([Cu(hfac)2]7(pyacbisNN)2, 2) formedby the reaction of a high spin nitronylnitroxide biradical C35H35N5O4 (pyacbisNN, 1) and bis(hexafluroacetylacetonate)copper(II) = Cu(hfac)2 are described. Single-crystal X-ray structure analysis revealed the triclinic P1̄ space groupof 2 with the following parameters: a =10.6191(4) Å, b = 19.6384(7) Å, c = 21.941(9) Å, α = 107.111(7)°, β= 95.107(8)°, γ = 94.208(0)°, Z = 2. Each repeating unit in 2 carries a centrosymmetric cyclic six spin and alinear five spin cluster with four different copper coordination environments having octahedral and square planargeometries. These clusters are interconnected to form infinite chains which are running along the crystallographicb axis. The magnetic measurements show nearly paramagnetic behavior with very small variations over a largetemperature range. The magnetic properties are thus result of complex competitions of many weak ferro- andantiferromagnetic interactions, which appear as small deviations from quite linear μeff vs T dependence at lowtemperature. At high temperature (300−14 K), antiferromagnetic behavior dominates a little, while at very lowtemperature (14−2 K), a small increase of μeff was observed. The magnetic susceptibility data are described by theCurie−Weiss law [χ = C/(T − θ)] with the optimal parameters C = 4.32 ± 0.01 emuK/mol and θ = − 0.6 ± 0.3K, where C is the Curie constant and θ is the Weiss temperature.
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