[NHN](-BOND IN ORGANIC RADICAL SOLID() HYDROGEN)

Reaction of m- or p-pyridyl nitronyl nitroxide (m- or p-PYNN) with HBr gas gave a 2:1 complex between them. The IR spectra of (m- and p-PYNN )(2)HBr indicates an intermolecular [NHN](+) hydrogen bond between two pyridyl rings. (m-PYNN)(2)HBr shows ferromagnetic properties, while t he p-isomer does antiferromagnetic properties. Furthermore, the HCl sa lt of phenyl-4-pyridylcarbene was generated by irradiation of the diaz o precursor. The ESR spectrum shows signals of triplet and quintet spi n species, latter of which indicates a ferromagnetic interaction betwe en the triplet carbenes.