Synthesis, structure, and magnetic properties of two dimer paddle-wheel CuII toluate complexes with nitronyl nitroxide radicals

Two new paddle-wheel dimeric copper complexes, [Cu-2(4-MePhCOO)(4)(NITmPy)(2)] (1) and [Cu-2(3-MePhCOO)(4)(NITmPy)(2)] (2) (NITmPy=2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro1H-imidazolyl-1-oxyl-3-oxide), were synthesized by reaction of copper toluate and NITmPy. Single crystal X-ray analyses revealed that both complexes are symmetrical dimers. Cu with four deprotonated methyl-benzoate bridging ligands form a paddle-wheel core and pyridyl nitrogen of radical ligands at the apical position. Based on the Cu-Cu axis of 1 and 2, we exploited the steric constraints of the methyl groups and induced the paddle-wheel. Two magnetic exchange pathways with strong antiferromagnetic interaction between dimeric Cu-II ions and weak antiferromagnetic interaction between NITmPy ligands exist in the complexes. IR and powder X-ray diffraction of the complexes were also studied.