A λ5-cylotriphosphazene with nitroxyl groups as model for a paramagnetic poly(organo-λ5-phosphazene)

Reaction of hexachlorocyclotriphosphazene (syst. name: 2,2,4,4,6,6-hexachloro-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphorine) ( 1 ) with 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (2a) gave the hexa-substituted λ⁵-cyclotriphosphazene 3a. Electron paramagnetic resonance spectra at low concentrations (10^?5 mol/L) showed a singlet only (no triplet) due to spin-spin exchange in the molecule. The paramagnetic molar susceptibility amounts to 7229 · 10^?6 cm³/mol at 300 K and does not depend on the magnetic field strength. 3a obeyed the Curie-Weiss law between 36 and 296 K demonstrating that there is no antiferromagnetic spin exchange.