title: Carbon Nanohoops: Excited Singlet and Triplet Behavior of Aza[8]CPP and 1,15-Diaza[8]CPP.
abstract: The excited state properties of two nitrogen-doped cycloparaphenylene molecules, or carbon nanohoops, have been studied using steady-state and time-resolved absorption and emission spectroscopies. Quantum yield of fluorescence (Φf = 0.11 and 0.13) and intersystem crossing (Φisc = 0.45 and 0.32) were determined for aza[8]CPP and 1,15-diaza[8]CPP, respectively. We also present the proton transfer reaction between trifluoroacetic acid and the nitrogen-doped nanohoops, which resulted in significant modifications to the steady-state absorption and emission spectra as well as the triplet-triplet absorption spectra. From fluorescence quenching data we determine the equilibrium constant for the proton transfer reaction between aza[8]CPP (Keq = 1.39 × 10(-3)) and 1,15-diaza[8]CPP (Keq = 2.79 × 10(-3)) confirming that 1,15-diaza[8]CPP is twice as likely to be protonated at a particular concentration of trifluoroacetic acid.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Hines
authors.affiliation: §Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.
authors.forename: Evan R
authors.initials: ER
authors.lastname: Darzi
authors.affiliation: §Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Hirst
authors.affiliation: §Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Jasti
authors.forename: Prashant V
authors.initials: PV
authors.lastname: Kamat