Abstract
Optically active 2,2-di-, 2,2,4,4-tetra- and 2,2,4,4,6,6-hexanitroxylcyclotriphosphazenes have been synthesized and their magnetic properties have been characterized. The variable-temperature magnetic susceptibilities of these radicals have been measured on a SQUID magnetometer down to 2K, showing antiferromagnetic interactions at low temperatures for all compounds. In order to investigate the intramolecular magnetic interactions in these radicals, magnetic susceptibility measurements of these radicals diluted in host molecules and EPR spectroscopic studies in the glassy solution of 2-MeTHF at 77K were carried out. Although no significant intramoleculer magnetic interactions were observed by magnetic susceptibility measurements for all compounds, the existence of the spin-spin exchange interactions in tetra- and hexaradical adducts were confirmed by the observations of the signals due to forbidden EPR transitions (Δms=+-2). On the other hand, diradical adducts did not show the signals in the Δms=+-2 region. From these results and the investigation of EPR spectrum of allowed transition, it seems that the distances between radical centers in tetra- and hexaradical adducts are shorter than those of 2,2-diradical adducts.
