Molecular structures and magnetic properties of the mixed-ligand complexesof 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 w ith bis(hexafluoroacetylaceonato)manganese(II), -copper(II), and -zinc(II) were prepared. An X-ray structure analysis of free ligand 4 reveals that th e molecule has a trans conformation with Ci symmetry and the aminoxyl radic al center has a short contact of 2.36 Angstrom with one of the neighboring molecules. The three 1:1 complexes have mutually similar molecular structur es 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 dis torted octahedron. The EPR experiments for free ligand 4 and [Zn-(hfac)(2). (hfac)(2). 4] in frozen solution suggested that the exchange couplings bet ween the two aminoxyls (R) through the 2,2'-bipyridine rings are antiferrom agnetic 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 me tal 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].