Helv. Chim. Acta, 86, 1026-1039 (2003)


The Structure of N1-Hydroxylophine N3-Oxide (=1-Hydroxy-2,4,5-triphenyl-1H-imidazole 3-Oxide) in the Solid State

The crystal structure of 1-hydroxy-2,4,5-triphenyl-1H-imidazole 3-oxide (1) has been determined from laboratory X-ray powder-diffraction data. The two independent molecules in the asymmetric unit form chains via OH⋅⋅⋅O hydrogen bonds related by a twofold screw axis. One of the O⋅⋅⋅O distances is extremely short (2.32(1) and 2.43(1) Å). Solid-state NMR spectroscopy (CPMAS) combined with calculation of absolute shieldings (GIAO/B3LYP/6-31G*) allowed us to determine that the compound behaves as if the OH⋅⋅⋅O hydrogen bond has the proton in the middle (single-well potential), resulting in the near identity of both 15N-NMR signals.