Synthesis, structures, and magnetic and optical properties of a series of europium(III) and gadolinium(III) complexes with chelating nitronyl and imino nitroxide free radicals.

This paper reports the synthesis, structures, and magnetic and optical properties of a series of gadolinium(III) (1a-4a) and europium(III) (1b-4b) complexes with nitronyl or imino nitroxide radicals. The crystal structures of compounds 1a and 1b consist of [Ln(III)(radical)(2)(NO(3))(3)] entities in which the gadolinium(III) (1a) or europium(III) ion (1b) is 10-coordinated to two nitronyl nitroxide radicals and three nitrato ligands. The crystal structures of compounds 2a-4a and 2b-4b consist of [Ln(III)(hfac)(3)(radical)] entities in which the gadolinium(III) (2a-4a) or europium(III) ion (2b-4b) is 8-coordinated to one nitronyl (2a and 2b) or one imino (3a, 4a and 3b, 4b) nitroxide radical and three hexafluoroacetylacetonato ligands.

The cyano nitronyl nitroxide radical: experimental and theoretical evidence for the fourth case of the McConnell-I mechanism.

The nitronyl nitroxide 2-cyano-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (1) crystallises in the tetragonal P42(1)m space group with a=7.4050(7), c=8.649(1) A.