Magneto-structural correlations in layered polymeric molecular ferromagnets based on Ni(II) and Co(II) complexes with 3-imidazoline nitroxide radicals and methanol with different substituents in the metal cycle

We report on the synthesis, structure, and magnetic properties of Ni(II) and Co(II) complexes with deprotonated enaminoketone derivatives of 3-imidazoline nitroxide radicals and methanol, ML₂(CH₃OH)₂. The complexes differ in substituents in the γ-position of the donor enaminoketone group (Cl, H, CH₃). When the substituents are varied, the magnetic behavior of these exchange clusters and their capability for three-dimensional ordering of magnetic moments at 5–7 K are not altered, and the arrangement of polymer layers remains constant. However, such variation of substituents is very important for the chemistry of these compounds. Thus the accepting ability of the central atom is reduced by substitution of the hydrogen atom by the methyl group but enhanced by substitution of halogen for hydrogen in the side chain of the enaminoketone. This favors a magnetic phase transition to a ferromagnetic state. The results obtained in this work are important for the chemical design of molecular ferromagnets based on metal bischelates with paramagnetic ligands. International Tomography Center, Siberian Branch, Russian Academy of Sciences. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 76–90, July–August, 1994. Translated by L. Smolina