Four Discrete Transition Metal Complexes Involving Pyridyl-substituted Nitronyl Nitroxide: Syntheses, Crystal Structures, and Magnetic Properties

Abstract

Four discrete metal-radical complexes, [Cu(p-MePh-COO)2(NITpPy)2] (1), [Ni(m-MePhCOO)2(NITpPy)2(H2O)2]·(CH3-OH)2 (2), [Mn(p-MePhCOO)2(NITpPy)2(H2O)2] (3), and [Mn(m-MePhCOO)2(NITpPy)2(H2O)2] (4) [NITpPy = 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide] were synthesized and characterized by elemental analyses, IR spectroscopy, PXRD, single-crystal X-ray diffraction, and magnetic susceptibility. For the four complexes, the crystal structural analyses indicate that the two radical ligands coordinated to the metal ions by the nitrogen atoms of the pyridine rings form three spin complexes, where toluates act as co-ligands. Weak antiferromagnetic interactions [JCu–Rad = –6.75 cm–1 (1), JCo–Rad = –4.15 cm–1 (2), JMn–Rad = –0.22 cm–1 (3), and JMn–Rad = –3.74 cm–1 (4)] were observed, spin polarization mechanism and orbital symmetry are used to explain the magnetic coupling in these complexes.