title: Aggregation-induced amplified quenching in conjugated polyelectrolytes with interrupted conjugation.
abstract: A pair of anionic conjugated polyelectrolytes that contain three-ring (phenylene ethynylene) units linked by a single -CH(2)- or -O- tether (P1 and P2, respectively) are studied. The linkers serve to interrupt the π conjugation along the polymer backbone. Fluorescence spectroscopy reveals that P2 forms a fluorescent aggregate in methanol and water; however, the fluorescence of P1 is much weaker in water, and P1 exhibits only weak aggregate fluorescence. Fluorescence quenching of the polymers was examined using methyl viologen (MV(2+)) as a cationic quencher. P1 shows only a weak amplified quenching effect, with a Stern-Volmer quenching constant of K(SV) ≈ 6 × 10(5) M(-1) in methanol. Interestingly, for P2 in methanol, the aggregate emission is strongly quenched with K(SV) ≈ 5 × 10(6) M(-1), which is comparable to the highest quenching efficiency observed for fully π-conjugated polyelectrolytes. By contrast, the monomer emission is quenched much less efficiently, with K(SV) ≈ 2 × 10(5) M(-1). The results are explained by a model in which -O- linked polymer P2 is able to fold into a helical conformation in solution, which facilitates the formation of extended π-stacked aggregates allowing long-distance exciton transport.
authors.affiliation: Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, USA.
authors.forename: Dongping
authors.initials: D
authors.lastname: Xie
authors.forename: Anand
authors.initials: A
authors.lastname: Parthasarathy
authors.forename: Kirk S
authors.initials: KS
authors.lastname: Schanze
mesh_terms: D000838:Anions / Q000737:chemistry; D004573:Electrolytes / Q000737:chemistry; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry
chemical_list: D000838:Anions; D004573:Electrolytes; D011108:Polymers; C473966:poly(phenylene ethynylene); D014867:Water