Magnetic exchange coupling tunable by means of selective cation binding into poly(radical-armed) azacrowns.

Host-guest complexes of tris(NN-CH2)-substituted 1,4,7-triazacyclononane and tetrakis(NN-CH2)-substituted 1,4,7,10-tetraazacyclododecane afforded the folded structures of the hosts where the NN radical oxygen atoms were coordinated to the guest metal ion, leading to enhanced antiferromagnetic couplings in the solid state and an ESR line broadening in the solution phase (NN = 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide).