4,6-Bis(trifluoromethyl)-N,N '-di-tert-butyl-1,3-phenylenebis(aminoxyl) and its bis(hexafluoroacetylacetonato)manganese(II) complex: synthesis, X-raycrystallography, and magnetism

Synthesis, crystallography, and magnetic characterization of bis(aminoxyl) 1 and its 2:1 complex with Mn(hfac)(2) (2) are described. X-ray structure o f 2 (at 20 K) provides one of the rare examples of discrete molecules found for the complexes of Mn(hfac), and bis(aminoxyls). The differences in conf ormations of the bis(aminoxyl) moieties in 1 and 2 lead to ferromagnetic an d antiferromagnetic exchange coupling through the 1,3-phenylene moiety, in 1 and 2, respectively, as determined by SQUID susceptometry. DFT calculatio ns (at the crystallographic geometries) give the triplet and the singlet gr ound states for 1 and for bis(aminoxyl) in 2, respectively. Two analogous c onformations of the bis(aminoxyl) are proposed to be responsible for the un precedented S-shaped time dependence for the conversion from the singlet to the triplet state of 1 in 2-methyltetrahydrofuran. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.