Three novel copper-radical complexes: Syntheses, crystal structures, and magnetic properties

Abstract

Three novel copper-radical complexes [Cu(PhCOO)2-(NITpPy) 2(H2O)2] (1), [Cu2(Me 3CCOO)4(NITpPy)2] (2), and [{Cu 2(Me3CCOO)4(NITpPy)}n] (3) [NITpPy = 4,4,5,5-tetramethyl-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· 2H2O 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 (J2 = 20.5 cm-1) take place in the copper radical when radicals coordinate the copper(II) ion with nitroxide directly. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.