Intramolecular excimer formation in naphthalene-containig polyesters. Bichromophoric model compounds derived from phathalic, siccinic or malonic acid and 2-hydroxynaphthalene or 2-hydroxy-methylnaphthalene.
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Steady state fluorescence measurements in dilute solutions are performed for bis(2-naphthyl) phthalate, bis(2-naphthylmethyl) phthalate, bis(2-naphthyl) succinate, bis(2-naphthylmethyl) succinate, bis(2-naphthyl) malonate and bis(2-naphthylmethyl) malonate, as models for polyesters containing naphthalene in their rigid units and flexible spacers that impose differences in the types of interactions between successive naphthalene units. The amount of intramolecular excimer in dilute solution depends on the type of flexible spacer, and also whether the compound is derived from 2-naphthol or 2-hydroxymethylnaphthalene. No excimer is detected from the compounds derived from 2-naphthol, but all compounds derived from 2-hydroxymethylnaphthalene showed excimer formation. These results are rationalized with a theoretical analysis of the conformations of the flexible spacers.