COMPLEXES OF METALS WITH PARAMAGNETIC 3-IMIDAZOLINE SCHIFF-BASES

Methods for the synthesis of intracomplex bischelates CuL2, NiL2, CoL2 , and the mixed-ligand complex NiL2Py2, where L is a deprotonated deri vative of the stable nitroxide yphenyl)-2,2,5,5-tetramethyl-3-imidazol ine-1-oxyl, were developed. In the solid state, the compounds have a m olecular structure. The most significant difference in the structure o f ML2 molecules lies in the values of the angle between the chelate ri ngs (56.9 degrees for CuL2, 78.8 degrees for CoL2, and 0 degrees for N iL2). in complexes with paramagnetic metal ions, the intramolecular ex change interactions are ferromagnetic in character and are close in th e order of magnitude (5.7 cm(-1) for CuL2 and 6.8 cm(-1) for NiL2Py2) to the values for complexes with deprotonated enaminoketone derivative s of 3-imidazoline. The NiL2 molecules, having a square coordination o f the central atom, are biradicals with antiferromagnetic exchange int eractions between the unpaired electrons of nitroxyl groups (-3.6 cm(- 1)). The transformation of NiL2 into NiL2Py2 leads to a transition of Ni(II) from the low- to high-spin state and to ferromagnetic exchange between the unpaired electrons of the paramagnetic centers.