1996/10/01 by Kensuke Togashi, Ron Imachi, Katsuyuki Tomioka +7
Biochemistry, Genetics and Molecular Biology · Materials Science · #Electron Spin Resonance Studies #Lanthanide and Transition Metal Complexes #Magnetism in coordination complexes
paper · doi:10.1246/bcsj.69.2821
crossref issued 1996/10/01 · crossref published 1996/10/01 · crossref published-print 1996/10/01 · openalex publication_date 1996/10/01 · crossref published-online 2006/06/28 · crossref created 2006/06/28 · crossref deposited 2024/01/20 · openalex created_date 2025/10/10 · crossref indexed 2026/07/29 · openalex updated_date 2026/07/30
Abstract A series of 4-arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyls (4-arylmethyleneamino-TEMPO) and related compounds were synthesized, and their magnetic susceptibilities were measured by a SQUID magnetometer in the temperature range of 1.8—100 K. Of 165 radicals investigated, 52 kinds of radicals exhibited intermolecular ferromagnetic interactions. These were confirmed by the increase of effective magnetic moments in low-temperature regions. Positive Weiss temperatures (θ), ranging from +0.03 to +0.75 K, were found for these materials. Over 100 kinds of radicals exhibited antiferromagnetic interactions with θ ranging from −0.01 to −24 K. The surprisingly high probability of finding organic radicals with intermolecular ferromagnetic interaction may be understood by the characteristic molecular arrangements in the crystals. An oxygen atom of an NO radical site of a piperidin-1-yloxyl moiety is apt to locate near methyl- and/or methylene-hydrogens of β-positions of the adjacent molecules, and the resultant spin polarization gives rise to parallel spin alignments of nearest NO sites in the crystals. 4-(4-Iodophenylmethyleneamino)-TEMPO exhibited a bulk ferromagnetic transition at 0.4 K. Six radicals exhibited metamagnetic transitions at magnetic fields lower than 200 Oe below 0.1 K.