title: Role of intersystem crossing in the fluorescence quenching of 2-aminopurine 2'-deoxyriboside in solution.
abstract: 2-Aminopurine is a fluorescent probe widely used to study local dynamics as well as charge and energy transfer reactions in DNA/RNA. Despite its broad utilization, the nonradiative relaxation pathways responsible for the variation in its fluorescence quantum yield and fluorescence lifetime in different solvents are still under scrutiny. In this work we use steady-state absorption and emission spectroscopy and broad-band transient absorption covering the time scale from femtoseconds to microseconds to investigate the excited-state dynamics of 2-aminopurine 2'-deoxyriboside (2APdr) in acetonitrile, ethanol, and aqueous buffer solution at pH 7. It is shown that up to ~40% of the initial excited-state population decays by intersystem crossing to the triplet state depending on the solvent used, thus competing effectively with fluorescence emission. Furthermore, the rate of formation and yield of the triplet state depend sensitively on the hydrogen-donor ability and polarity of the solvent.
authors.affiliation: Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Reichardt
authors.forename: Chengwei
authors.initials: C
authors.lastname: Wen
authors.forename: R Aaron
authors.initials: RA
authors.lastname: Vogt
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Crespo-Hernández
mesh_terms: D015075:2-Aminopurine / Q000737:chemistry*; D000097:Acetonitriles / Q000737:chemistry; D003853:Deoxyribonucleosides / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D011789:Quantum Theory; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence
chemical_list: D000097:Acetonitriles; D003853:Deoxyribonucleosides; D005456:Fluorescent Dyes; D012996:Solutions; D012997:Solvents; D000431:Ethanol; D015075:2-Aminopurine; C032159:acetonitrile