Crystal Packing and Magnetism in Phenolic Nitronylnitroxides: 2-(3 `,5 `-Dimethoxy-4 `-hydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl

2-(3′,5′-Dimethoxy-4′-hydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (SyrNN) forms a hydrogen bonded network of contacts involving phenolic OH and nitronylnitroxide methyl groups as donors, and nitronylnitroxide NO groups as acceptors. The SyrNN intermolecular contact network is quite similar to that of 2-(4′-hydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (HOPhNN) (Cirujeda et al., J. Mater. Chem. 1995, 5, 243–252), which shows ferromagnetic exchange interactions, but SyrNN has an additional antiparallel stacking contact between nitronylnitroxide NO groups that qualitatively and computationally is expected to induce antiferromagnetic (AFM) exchange between SyrNN molecules. Experimentally, the magnetism of SyrNN shows evidence of multiple exchange interactions with overall low dimensional AFM exchange behavior. Fits of dc magnetic susceptibility versus temperature data for SyrNN to AFM 1-D chain and 2-D square planar models give J/k ∼ (−)1–3 K.