Preparation of poly(phenyl)acetylenes having diazo groups and magnetic characterization of poly(carbene)

(2,6-Dibromo-4-ethynylphenyl)(2,6-dimethyl-4-tert-butylphenyl)diazomethane was found to be stable enough to survive under Rh-complex-catalyzed polymerization conditions and underwent polymerization to give a phenylacetylene polymer having diazo functional groups intact with an average molecular weight of 86 000 (polystyrene standard). The products from irradiation of the polymer were characterized by SQUID measurements, which revealed that a persistent triplet carbene unit incorporated into a pi-network of the phenylacetylene polymer indeed acts as a spin source to generate a high-spin ground state, although the estimated spin multiplicities are not as high as that expected from the degree of polymerization. The finding unequivocally shows that a precursor diazo unit can basically be handled as a building block to construct polydiazo compounds and that persistent triplet carbenes, even though they greatly lose typical reactivity as a triplet carbene, still retain electronic properties and act as a spin source when aligned properly in the pi-electron frameworks to generate a high-spin molecule.