title: 2-phenoxathiinyl-5-phenyloxazole and 5-phenoxathiinyl-2-phenyloxazole derivatives: experimental and theoretical study of emission properties.
abstract: The absorption and emission spectra in cyclohexane and methanol of the title phenoxathiinyl-phenyloxazole derivatives are presented and discussed. Comparing to the unsubstituted diphenyloxazole (PPO), the experimental results show a bathochromic shift of the emission band, a significant dependence of the maximum on the solvent polarity and a drastic decrease of the fluorescence quantum yield. Semiempirical MO calculations (AM1) in both the ground and excited states support the experimental findings. A charge transfer from the phenoxathiin fragment to the oxazole ring is predicted in the excited state explaining the solvatochromism of the compounds. The values for the singlet-triplet gap, 3500-5000 cm-1 point to an enhanced probability of intersystem crossing (ISC) non-radiative deactivation processes, in agreement with the low fluorescence quantum yields.
authors.affiliation: University of Bucharest, Faculty of Chemistry, Department of Physical Chemistry, Bd. Regina Elisabeta, 4-12, Bucharest, Romania. sorana@gw-chimie.math.unibuc.ro
authors.forename: Sorana
authors.initials: S
authors.lastname: Ionescu
authors.forename: Daniela
authors.initials: D
authors.lastname: Popovici
authors.forename: Alexandru T
authors.initials: AT
authors.lastname: Balaban
authors.forename: Mihaela
authors.initials: M
authors.lastname: Hillebrand
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D003510:Cyclohexanes / Q000737:chemistry; D000432:Methanol / Q000737:chemistry; D008956:Models, Chemical; D010080:Oxazoles / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D055672:Static Electricity
chemical_list: C519787:5-phenoxathiinyl-2-phenyloxazole; D000097:Acetonitriles; D003510:Cyclohexanes; D010080:Oxazoles; C506365:Cyclohexane; D000432:Methanol; C032159:acetonitrile