High-spin polyphenoxyl based on poly(1,4-phenyleneethynylene)

Rodlike poly(1,4-phenyleneethynylene) 2-substituted with multiple pendant phenoxyls 1 was synthesized by polymerizing 4-bromo-2-(3,5-di-tert- butyl-4-hydroxyphenyl)ethynylbenzene 10a using the catalyst of a palladium- triphenylphosphine complex and cuprous iodide and subsequent heterogeneous oxidation. The corresponding dimer 2 was also synthesized; X-ray analysis of its precursor 4 indicated a linear phenyleneethynylene backbone and twisted dihedral angles of 50 and 77°for the pendant phenol groups. ESR spectra suggested a delocalized spin distribution from the pendant phenoxyl to the backbone. The diphenoxyl 2 had a triplet (S = 2/2) ground state. The spin concentration of the polyphenoxyl 1 could not be increased beyond 0.7 spin/unit due to its low solvent solubility; 1 with a spin concentration of 0.62 had an average S of 3/2.