Magnetic properties after irradiation of poly(m-phenyleneethynylene) having diazo and nitronylnitroxide groups and its model compounds

In order to achieve a pure organic high-spin molecule, poly(m-phenyleneethynylene) derivative 1 having diazo groups and nitronyl nitroxide moieties alternately were designed. Its three model compounds, diphenylacetylene derivative 2, bis(phenylethynyl)benzene derivative 3, and oligomeric compound 4 having partial structure of 1 have been prepared by the coupling reaction of ethynyl derivatives of phenylnitronylnitroxide and iodo derivatives of diphenyldiazomethane. Field dependence of magnetization after irradiation of 2 and 3 in frozen solutions suggested that the photo-generated species have quartet and quintet ground states with J/k_B values of + 1.75 and + 1.09 K, respectively. However, spin interaction between carbene and nitronylnitroxide through 3,3-diphenylacetylene moiety is not strong enough to form high-spin chain having long correlation length for 4.