Aminophenylnitronylnitroxides: highly networked hydrogen-bond assembly in organic radical materials.

2-(Meta-aminophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (mAPN) and 2-(para-aminophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (pAPN) were synthesized and subjected to magnetostructural analysis. Both form extended hydrogen bonding networks involving both amino NH bonds to radical spin-density bearing nitronylnitroxide NO groups. Their crystallographic assembly motifs and magnetic exchange properties are compared to those of tert-butoxylcarbonyl (BOC) and amide derivatives having only one NH bond. The conversion of pAPN to acid salt derivatives gives a solid that is essentially diamagnetic, although dissolution of the solid shows the radical spin units to be preserved.