Oxamido-Bridged Bimetallic Complexes Involving Nitronyl Nitroxide Radical Ligands: Crystal Structure and Magnetic Behavior

Two novel dinuclear copper(II) complexes containing four spin carriers have been synthesized and
characterized structurally and magnetically. These complexes are formulated as [Cu2(apox)(NIT-4Py)2](ClO4)2·2H2O
(1) and [Cu2(apox)(NIT-2Py)2](ClO4)2 (2), where apox = N,N‘-bis(3-aminopropyl) oxamido, NIT-4Py = 2-(4‘-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and NIT-2Py = 2-(2‘-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. The structure of complexes 1 and 2 consists of centrosymmetric trans oxamido-bridged copper(II) binuclear
units. In complex 1, the coordination geometry of the copper atom is distorted square plane and the radical ligands
(NIT-4Py) coordinate to the copper atoms via the nitrogen atoms of the pyridine ring, whereas in complex 2, the
coordination geometry around each copper atom is distorted square pyramidal and the apical position is occupied
by an oxygen atom of the radical ligand. Magnetic analyses indicate that both compounds 1 and 2 exhibit strong
antiferromagnetic coupling between copper(II) ions through the oxamido bridge and there are ferro- and
antiferromagnetic exchange interactions between copper(II) ions and radical ligands for compounds 2 and 1,
respectively.