Synthesis and properties of paramagnetic derivatives of linear and fused polyaromatic compounds

Paramagnetic derivatives of tolan, anthracene, and terphenyl of the A−Sp−R• type, where A is an aromatic group, R• is a stable radical center, and Sp is a spacer, were synthesized. The electronic absorption and luminescence spectra of these compounds were examined. The introduction of the paramagnetic dihydroimidazole fragment causes a decrease (10–500-fold) in the quantum yield of luminescence compared to emission of the individual aromatic luminophore. The presence of a radical center (R•) in the (alkane)•+/−•A−Sp−R• radical-ionic pair leads to the disappearance or fast (nanoseconds) damping of the magnetic effect of luminescence arising upon recombination of these pairs.