Preparation and Magnetic Properties of Metal-Complexes from N‑t‑Butyl‑N‑oxidanyl-2-amino-(nitronyl nitroxide)

Metal complexation reactions of N-t-butyl-N-oxidanyl-2-amino­(nitronyl nitroxide) diradical (1) with M­(hfac)2 (M: Mn or Cu) were investigated. These reactions were found to be very sensitive to the type of metal ion employed. Complex [Mn­(hfac)2·1], consisting of Mn­(hfac)2 and diradical 1, was readily prepared by mixing the components. However, the reaction of Cu­(hfac)2 with 1 or N-t-butyl-N-oxidanyl-2-amino­(iminonitroxide) diradical (2) involved the reduction of the diradical to the N-t-butyl-N-oxidanide-2-amino­(iminonitroxide) radical anion (3) and finally produced the polymer-chain complex [Cu2(hfac)2·32·Cu­(hfac)2]n. The structures of these complexes were elucidated by X-ray analysis, and their magnetic properties were investigated in detail. The temperature dependence of χpT (χp: magnetic susceptibility) for [Mn­(hfac)2·1] exhibited a strong antiferromagnetic interaction (H = −2JS1·S2, J/kB = −217 K) between the Mn­(II) spin (S = 5/2) and the diradical 1 spin (S = 1). However, the χpT–T plots for [Cu2(hfac)2·32·Cu­(hfac)2]n indicated the presence of several magnetic interactions: a large ferromagnetic interaction (J/kB = 510 K) between iminonitroxide 3 and the imino-coordinating Cu­(II) atom, a moderately large ferromagnetic interaction (J/kB = 58 K) between the iminonitroxide and (iminonitroxide oxygen)-coordinating Cu­(hfac)2, and a weak antiferromagnetic interaction (J/kB = −1.4 K) between the two Cu­(hfac)-3 moieties within a Cu2O2 square.