Three Novel Copper-Radical Complexes: Syntheses, Crystal Structures, and Magnetic Properties

Three novel copper-radical complexes [Cu(PhCOO)(2)-(NITpPy)(2)(H2O)(2)] (1), [Cu-2(Me3CCOO)(4)(NITPPY)(2)] (2), and [{Cu-2(Me3CCOO)(4)(NITpPy)}(n)] (3) [NITpPy = 4,4,5,5-tetra-methyl-2-(4-pyridyl)-2-imidazoline-1-oxyl 3-oxide] were synthesized and characterized structurally as well as magnetically. It is noteworthy that the syntheses of complexes 2 and 3 are similar except for the temperature of the reaction between Cu(Me3CCOO)(2)center dot 2H(2)O and the NITpPy radical ligand. Our magnetic study of complexes 1 and 2 reveals that the antiferromagnetic interactions occur with a J value around -10 cm(-1) between copper(II) and radicals when radicals use the pyridine nitrogen atom connected to the copper(II) ion. Yet the best-fit parameters of complex 3 reveal that significant ferromagnetic interactions (J(2) = 20.5 cm(-1)) take place in the copper radical when radicals coordinate the copper(II) ion with nitroxide directly.