Methods of synthesising stable 2-imidazoline nitroxides linked to a pyrazol
e moiety either directly or through a phenylethynylic bridge have been deve
loped; an unusually strong temperature dependence of mu(eff) for 2-(1-methy
lpyrazolyl-5)-4,4,5,5-tetramethyl-1-oxyI-2-imidazoline-3-oxide is observed.