Molecular structures and magnetic properties of the mixed-ligand complexes of bis(hexafluoroacetylacetonato)manganese(II), -copper(II), and -zinc(II) with 4,4'-bis(N-tert-butyl-N-oxylamino)-2,2'-bipyridine. Isosceles triangular hetero-three-spin systems consisting of aminoxyls and metal ions

4,4'-Bis(N-tert-butyloxylamino)-2,2'-bipyridine (4) and its 1:1 complexes with bis(hexafluoroacetylacetonato)-manganese(II), -copper(II), and -zinc(II) were prepared. An X-ray structure analysis of free ligand 4 reveals that the molecule has a trans conformation with C(i) symmetry and the aminoxyl radical center has a short contact of 2.36 Å with one of the neighboring molecules. The three 1:1 complexes have mutually similar molecular structures in which the 2,2'-bipyridine moiety has a cis conformation and serves as a bidentate ligand and coordination geometry around the metal atom is a distorted octahedron. The EPR experiments for free ligand 4 and [Zn(hfac)²·4] in frozen solution suggested that the exchange couplings between the two aminoxyls (R) through the 2,2'-bipyridine rings are antiferromagnetic with J(R-R)/k(B) = -19.3 ± 0.5 and -24.3 ± 0.4 K, respectively. Isosceles triangular three-spin models were applied to the 1:1 magnetic metal complexes to give J(R-M)/k(B) = -19.1 ± 0.2 K and J(R-R)/k(B) = -32.9 ± 0.3 K for [Mn(hfac)₂·4] and J(R-M)/k(B) = +73 ± 18 K and J(R-R)/k(B) = -24.5 ± 6.5 K for [Cu(hfac)₂·4].