作者:Eugene V. Tretyakov、Svyatoslav E. Tolstikov、Elena V. Gorelik、Matvey V. Fedin、Galina V. Romanenko、Artem S. Bogomyakov、Victor I. Ovcharenko
DOI:10.1016/j.poly.2007.11.003
日期:2008.2
It was established that the reactions of pyrazol-3-yl-substituted nitronyl nitroxide (HL') and pyrazol73-yl-substituted imino nitroxide (HL3) with Cu(II) acetate lead to self-assembly of the Cu-4(OH)(2)(OAc)(4)(DMF)(2)(L-1)(2) tetranuclear and Cu-2(OAc)(2)(H2O)(2)(L-3)(2) dinuclear complexes, respectively. The reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted nitronyl nitroxide (HL2) gave unexpected solid Cu-2(H2O)(2)(L-6)(2) center dot 2DMF, in which L-6 is a deprotonated 5-carboxy-pyrazol-3-yl-substituted nitronyl nitroxide, formed as a result of cleavage of an ester bond in the starting HL2. A similar transformation of the paramagnetic ligand was observed in the reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted imino nitroxide (HL4). It led to the formation Of Cu-2(DMF)(2)(L-7)(2), where L-7 is deprotonated 2-(5-carboxy-lH-pyrazol-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide. An X-ray diffraction study indicated that in Cu-4(OH)(2)(OAc)(4)(DMF)(2)(L-1)(2) and Cu-2(OAc)(2)(H2O)(2)(L-3)(2), the L-1 and L-3 paramagnetic ligands perform the bridging cyclic tridentate function, while in Cu-2(H2O)(2)(L-6)(2)center dot 2DMF and Cu-2(DMF)(2)(L-7)(2), the paramagnetic L-6 and diamagnetic L-7 are bridging bicyclic tetradentate ligands. The magnetic behavior of complexes with coordinated nitronyl nitroxide - Cu-4(OH)(2)(OAc)(4)(DMF)(2)(L-1)(2) and Cu-2(H2O)(2)(L-6)(2) center dot 2DMF is dictated by the dominant antiferromagnetic exchange interactions, which is confirmed by quantum-chemical data. The magnetic susceptibility of Cu-2(OAC)(2)(H2O)(2)(L-3)(2) reflects the competition between the antiferromagnetic and ferromagnetic components, of which the latter is due to electron coupling in the Cu(II) <- N=C-N (center dot) under bar O exchange channels. EPR data confirm the results received from static magnetic measurements for multispin solids. (c) 2007 Elsevier Ltd. All rights reserved.