THE FORSTER RADIUS FOR ENERGY-TRANSFER FROM NAPHTHALENE TO ANTHRACENEIN POLYESTERS WITH OXYETHYLENE SPACERS

Model compounds for a series of polyesters in which 3,6,9, and 12-rota table CH2-O and CH2-CH2 bonds separate rigid units have been studied u sing the efficiency of nonradiative singlet energy transfer from napht halene to anthracene. The model compounds have the structure naph-CO-( OCH2CH2)(m)-OOC-anth with m of 1-4, where naph and anth denote 2-napht hyl and 9-anthranyl groups, respectively. This series of compounds cov ers a larger range of potential separation of the two chromophores tha n was possible in an earlier study, in which the flexible spacers cons isted of 2-6 methylene units. The nonradiative singlet energy transfer has an efficiency that depends on the solvent viscosity and on m. The theoretical analysis employs a rotational isomeric state model for th e conformations of these molecules. The Forster radius for transfer fr om naphthalene to anthracene in this system is 16 +/- 2 Angstrom, and is nearly independent of whether the spacers are constructed from oxye thylene or methylene units.