Acta Crystallographica Section B

Structural Science

Volume 55, Part 2 (April 1999)

Acta Cryst. (1999). B55, 231-245 [doi:10.1107/S0108768198012786]

TEMPO radicals showing magnetic interactions. I. 4-(4-Halobenzylideneamino)TEMPO and related compounds

F. Iwasaki, J. H. Yoshikawa, H. Yamamoto, E. Kan-nari, K. Takada, M. Yasui, T. Ishida and T. Nogami

Abstract: X-ray crystal structure analyses of the 4-(4-halobenzylideneamino)TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidyl-1-oxyl) radicals 4-(4-fluorobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl, 4-(4-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl, 4-(4-bromobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl and 4-(4-iodobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl, and other 4-Ar-CH=N-TEMPO [Ar = 4-Ph-Ph, 2,2,6,6-tetramethyl-4-(4-phenylbenzylideneamino)piperidyl-1-oxyl, 4-Py, 2,2,6,6-tetramethyl-4-(4-pyridylmethylideneamino)piperidyl-1-oxyl, and 3,5-diCl-Ph, 4-(3,5-dichlorobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl] radicals have been performed at room temperature. Some of these radicals show intermolecular ferromagnetic interactions at extremely low temperatures. X-ray analysis revealed that crystals of the 4-I-Ph derivative showed two modifications [(a) and (b)]; measurements of the magnetic properties of these crystals showed a ferromagnetic transition at an extremely low temperature for modification (a) and an antiferromagnetic interaction for modification (b). The structural features of these TEMPO radical crystals can be classified into three groups: (i) the crystal structures of the 4-Cl-Ph, 4-I-Ph(a) and 4-Ph-Ph derivatives, which show a ferromagnetic transition; (ii) the structures of the 4-Br-Ph and 4-Py derivatives, which show a ferromagnetic interaction ( [bold theta] > 0); (iii) miscellaneous: the antiferromagnetic 4-F-Ph and 4-I-Ph(b) derivatives ( < 0) and the ferromagnetic 3,5-diCl-Ph ( > 0) derivative. Sheet-like arrangements of O atoms and intra-sheet interactions through the CH₂ or CH₃ groups of the TEMPO rings are related to the mechanisms of the ferromagnetic interactions.

Online 1 April 1999


	Structure factor file (CIF format) (178.7 kbytes) Contains datablock 1

	Structure factor file (CIF format) (179.0 kbytes) Contains datablock 2

	Structure factor file (CIF format) (187.3 kbytes) Contains datablock 3

	Structure factor file (CIF format) (188.3 kbytes) Contains datablock 4-I-Ph-CH=N-TEMPO(4a)

	Structure factor file (CIF format) (388.9 kbytes) Contains datablock 4-I-Ph-CH=N-TEMPO(4b)

	Structure factor file (CIF format) (214.2 kbytes) Contains datablock 5

	Structure factor file (CIF format) (166.6 kbytes) Contains datablock 6

	Structure factor file (CIF format) (194.0 kbytes) Contains datablock 7

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