POLY(PHENYLENEVINYLENE)-ATTACHED PHENOXYL RADICALS - FERROMAGNETIC INTERACTION THROUGH PLANARIZED AND PI-CONJUGATED SKELETONS

Chemically stable tert-butyl-4-oxyphenyl)-1,4(p)-phenylenevinylene], t ert-butyl-4-oxyphenyl)-1,3(m)-phenylenevinylene], and -tert-butyl-4-ox yphenyl)-1,2(o)-phenylenevinylene] were synthesized via the polymeriza tion of romo-2-(3,5-di-tert-butyl-4-acetoxyphenyl)styrene, 5-bromo-2-( 3,5-di-tert-butyl-4-acetoxyphenyl) styrene, and 2-bromo-4-(3,5-di-tert -butyl-4-acetoxyphenyl) styrene, respectively, using a palladium catal yst. The o- and p-polyradicals, even with their spin concentration of 0.6 spin/unit, displayed S values of 4/2 to 5/2 (S = 5/2 for the o-pol yradical with a degree of polymerization of 17 and a spin concentratio n of 0.68), while the m-polyradical has a singlet ground state. A long -range intramolecular through-bond ferromagnetic exchange interaction was realized between the pendant unpaired electrons for the o- and p-p olyradicals, in accordance with theoretical predictions based on the m olecular connectivity. The average value of the exchange coupling cons tant for the o-polyradical, 2 (J) over bar = 48 +/- 6 cm(-1), was larg er than 2 (J) over bar = 32 +/- 2 cm(-1) for the p-polyradical, while they were almost coincident with or much larger than the exchange coup ling constants for the corresponding diradical model compounds. Both f orce field calculations and spectroscopic results indicated a less hin dered steric structure with a planarized pi-conjugated skeleton for th e o-polyradical.