Molecular-level chromophore-quencher assemblies have been prepared in precast chlorosulfonated polystyrene ([-CH2CH(p-C6H4SO2Cl)]x-; PS-SO2Cl) films by (1) exposing the intact film to solutions containing the chromophore [(bpy)2Ru(5-NH2Phen)][PF6]2 (bpy is 2,2′-bipyridine; 5-NH2phen is 5-amino-1,10-phenanthroline) which becomes chemically bound through sulfonamide bond formation, (2) partially hydrolyzing a portion of the remaining -SO2Cl sites to -SO3 - sites and exposing the resulting films to acetonitrile solutions containing the electron-transfer quencher paraquat (PQ2+) and the reductive scavenger triethanolamine (N(C2H4OH)3). The photophysical properties of the chromophore-based metal-to-ligand charge-transfer excited state have been investigated by lifetime and visible absorption and emission spectra. Although similar to related monomers, excited-state decay in the films is nonexponential. The dynamics of excited-state quenching by PQ2+ following pulsed laser excitation show that the chromophore occupies three different chemical sites within the films. At one site, which accounts for ∼50% of the emitted light and appears to be located near ion channels created by hydrolysis, quenching is rapid, KSV ∼ 6.8 × 104 M-1. A second site exists that undergoes relatively slow quenching, KSV ∼ 3 × 103 M-1, and then only with added [NEt4](ClO4). A third site is present that is not quenched.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry