Influence of Solvent Polarity and Viscosity on Nonradiative Processes in Oligothiophenes with Intramolecular Charge Transfer |
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Authors: | S L Bondarev V N Knyukshto S A Tikhomirov I I Kalosha D N Bobrov N V Masalov N M Nevar V I Tyvorskii A V Kel'in O G Kulinkovich K Dziliński |
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Institution: | (1) Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 F. Skorina Ave., 220072 Minsk, Belarus;(2) Belarusian State University, Minsk;(3) Polytechnical Institute, Czestochowa, Poland |
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Abstract: | By the methods of luminescence, picosecond spectroscopy, and quantum chemical calculations the mechanisms of electron excitation energy deactivation in some oligothiophenes with intramolecular charge transfer depending on the solvent polarity and viscosity have been investigated. While for 2 N piperidino 5 (2 ,2![prime](/content/0mkludtt3t5l35qe/xxlarge8242.gif) dicyanovinyl)thiophene (PDCVT) the main channel of nonradiative deactivation is the transition to a lower intermediate state with a twisted double bond controlled by the medium viscosity, in the case of (E) {2 2 5 piperidino 2 thienyl] 6 (trifluoridemethyl) 4H 4 pyranylidene}propanedinitryl (PTFDN) fluorescence quenching is initiated by the solvent polarity. For two other oligothiophenes, 2 N piperidino 5 cyanothiophene (PCT) and 2 N piperidino 5![Prime](/content/0mkludtt3t5l35qe/xxlarge8243.gif) cyanoterthiophene (PCTT), differing in the length of the thiophene chain, we have revealed, along with the effective quenching of fluorescence in short chain PCT (independent of the solvent polarity and viscosity), an increase in the radiation capacity in PCTT with increasing polarity of the solvent. The possible mechanisms of nonradiative deactivation in the investigated oligothiophenes are discussed. |
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Keywords: | fluorescence change transfer polarity viscosity fluorescence quenching |
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