CRYSTAL-STRUCTURE OF ORGANIC METAMAGNET - 4-METHACRYLOYLOXY-2,2,6,6-TETRAMETHYL-1-PIPERIDINYLOXYL (MOTMP)

Structures of 4-methacryloyloxy-2,2,6,6-tetramethyl-1-piperidinyloxyl (MOTMP) and 4-acryloyloxy-2,2,6,6-tetramethyl-1-piperidinyloxyl (AOTMP) which have one-dimensional ferromagnetic coupling and antiferromagnetic interactions, respectively, have been determined by X-ray crystallographic analysis. The crystals of both compounds are monoclinic and have space group P2(1) (No. 4) with Z = 2. The one-dimensional ordering of spins of NO radicals is explained by intermolecular superexchange interactions of NO radicals due to NO radical ...C=C-C=O...NO radical contacts shorter than the van der Waals radii sum (ca. 3.6 angstrom). The difference in magnetic behavior between MOTMP and AOTMP might be due to the difference in the torsion angle of the C=C-C=O moiety, as in the three-dimensional molecular arrangement in the crystals.