Photoluminescence of ortho-bromobenzophenone

• Veröffentlicht in: Физика низких температур
• Datum: 2006
• ISSN: 0132-6414
• Hauptverfasser: Avdeenko, A.A., Pyshkin, O.S., Eremenko, V.V., Strzhemechny, M.A., Buravtseva, L.M., Romashkin, R.V.
• Format: Artikel
• Sprache: Englisch
• Veröffentlicht: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2006
• Schlagworte: Molecular Solids
• Online Zugang: https://nasplib.isofts.kiev.ua/handle/123456789/120880
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Zitieren: Photoluminescence of ortho-bromobenzophenone / A.A. Avdeenko, O.S. Pyshkin, V.V. Eremenko, M.A. Strzhemechny, L.M. Buravtseva, R.V. Romashkin // Физика низких температур. — 2006. — Т. 32, № 11. — С. 1355–1362. — Бібліогр.: 36 назв. — англ.

Phosphorescence spectra of crystalline ortho-bromobenzophenone (2-bromobenzophenone,
 2BrBP) were measured from 1.6 K to room temperature. A cardinal emission mechanism crossover
 occurs within this temperature range. At low temperature the phosphorescence spectrum is a
 superposition of two similar sets of equidistant bands spaced by the C=O stretch frequency. We
 ascribe these two sets to the emission of two different conformers, one of which is metastable and
 do not manifest itself above approximately 70 K. Presence of two conformers is explained by the
 fact that the 2BrBP molecule deforms considerably upon excitation. The emission from the stable
 conformer survives up to approximately 140 K or even higher. At roughly 60 K and higher, another
 type of emission reveals itself in the shape of a two very broad partly overlapping bands, which
 gains in intensity with increasing temperature. Above 150 K only this two-hump feature is
 observed in phosphorescence spectra. Additional phosphorescence experiments were carried out to
 elucidate the nature of this spectrum, including phosphorescence measurements of 2BrBP in
 ethanol solutions as well as time-resolved and varying-excitation-intensity measurements from
 crystals. Based on results of all the experiments reported here and on our own single-crystal x-ray
 structure data we conclude that the above two-band spectrum recorded near room temperature is
 due to the emission of single-photon bimolecular triplet excimer formed by the carbonyl groups of
 two neighbor 2-bromobenzophenone molecules. It is got the first time that a bimolecular excimer
 has been observed and reliably identified in a benzophenone derivative solid.