Method for enhancing the sensitivity of fluorescent chemosensors: energy migration in conjugated polymers.

A new method for the enhancement of a fluorescent chemosensory response using conjugated polymers is reported. This method makes use of the delocalized electronic structure of these materials which allows the excited state to migrate to an occupied receptor site. In the conjugated polymer I each repeating unit displays a cyclophane receptor which binds paraquat (Ka ≈ 1600 M-1). The binding of paraquat to I and II results in electron transfer quenching. The relative amt. of quenching in I is enhanced relative to II due to energy migration to the occupied sites. Theor., I can exhibit a max. sensitivity which is n times greater than II where n is the d.p. This effect leads to an enhancement in the static quenching consts. as detd. by the Stern-Volmer relation from 1600 M-1 for I to 105,000 M-1 for II (Mn = 122,500). Polymers lacking receptor groups also displayed enhanced dynamic quenching consts. relative to monomeric analogs. [on SciFinder(R)]