title: Carbon nanohoops: excited singlet and triplet behavior of [9]- and [12]-cycloparaphenylene.
abstract: Cycloparaphenylene molecules, commonly known as "carbon nanohoops", have the potential to serve as building blocks in constructing carbon nanotube architectures. The singlet and triplet excited-state characteristics of [9]-cycloparaphenylene ([9]CPP) and [12]-cycloparaphenylene ([12]CPP) have now been elucidated using time-resolved transient absorption and emission techniques. The fluorescence quantum yields (Φ) of [9]CPP and [12]CPP were determined to be 0.46 and 0.83, respectively. Rates of nonradiative recombination (knr), radiative recombination (kr), and intersystem crossing (kisc) determined in this study indicate that radiative decay dominates in these nanohoop structures. The triplet extinction coefficient was determined through energy transfer with biphenyl, and the triplet quantum yield (ΦT) was calculated to be 0.18 and 0.13 for [9]CPP and [12]CPP, respectively. The rate of triplet state quenching by oxygen was measured to be 1.7 × 10(3) ([9]CPP) and 1.9 × 10(3) s(-1) ([12]CPP). The excited-state dynamics established in this study enable us to understand the behavior of a carbon nanotube-like structure on a single subunit level.
authors: Notre Dame Radiation Laboratory and ‡Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors: Douglas A
authors: DA
authors: Hines
authors: Evan R
authors: ER
authors: Darzi
authors: Ramesh
authors: R
authors: Jasti
authors: Prashant V
authors: PV
authors: Kamat
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry*; D015394:Molecular Structure; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D001555:Benzene Derivatives; D037742:Nanotubes, Carbon