Abstract: A nitroxide radical of the formula (I) or (II): ##STR1## in which R.sub.1 and R.sub.2 are independently chosen from among the optionally deuterated alkyl, alkoxyl, dialkylaminyl and phenyl radicals, H, D or Cl; R.sub.3, R.sub.8 and R.sub.9 are independently chosen from among the optionally deuterated alkyl, alkoxyl and phenyl radicals; R.sub.4, R.sub.5, R.sub.6 and R.sub.7 are independently chosen from among the optionally deuterated alkyl, alkoxyl, dialkylaminyl and phenyl radicals, COOH, OH, OD, H, D, a halogen, COOR (in which R is an alkyl radical); R.sub.10 and R.sub.11 are independently chosen from among optionally deuterated alkyl, alkoxyl, dialkylaminyl and phenyl radicals, COOH, OH, OD, H, D, a halogen, COOR (in which R is an alkyl radical) or represent an oxygen atom linked with the cycle of the radical by a double bond is described.

Abstract: The invention concerns an octasubstituted lithium phthalocyanine responding to the formula: ##STR1## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8, which are identical or different, represent an alkyl or alcoxy radical, possibly substituted by fluorine, and M represents Li or Li.sub.2.When M represents Li, this involves a lithium phthalocyanine octasubstituted like a radical which can be used in electronic paramagnetic resonance magnetometry.In this case, the substituents are preferably all identical and represent the methyl or methoxy radical.