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

摘要

Synthesis, crystallography, and magnetic characterization of bis(aminoxyl) 1 and its 2:1 complex with Mn(hfac)_2 (2) are described. X-ray structure of 2 (at 20 K) provides one of the rare examples of discrete molecules found for the complexes of Mn(hfac)_2 and bis(aminoxyls). The differentces in conformations of the bis(aminoxyl) moieties in 1 and 2 lead to ferromagnetic and antiferromagnetic exchange coupling through the 1,3-phenylene moiety, in 1 and 2, respectively, as determined by SQUID susceptometry. DFT alculations (at the crystallographic geometries) give the triplet and the singlet ground states for 1 and for bis(aminoxyl) in 2, respectively. Two analogous conformations of the bis(aminoxyl) are proposed to be responsible for the uprecedented S-shaped time dependence for the conversion from the singlet to the triplet state of 1 in 2-methyltetrahydrofuran.