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Preparation and Magnetic Properties of Metal-Complexes from N‑t‑Butyl‑N‑oxidanyl-2-amino-(nitronyl nitroxide)
journal contribution
posted on 2014-01-21, 00:00 authored by Takanori Furui, Shuichi Suzuki, Masatoshi Kozaki, Daisuke Shiomi, Kazunobu Sato, Takeji Takui, Keiji Okada, Evgeny V. Tretyakov, Svyatoslav
E. Tolstikov, Galina V. Romanenko, Victor I. OvcharenkoMetal
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.
