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

Three novel copper-radical complexes [Cu(PhCOO) 2 -(NITpPy) 2 (H 2 O) 2 ] (1), [Cu 2 (Me 3 CCOO) 4 (NITpPy) 2 ] (2), and [{Cu 2 (Me 3 CCOO) 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(Me 3 CCOO) 2 ·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.

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