Fluorescence Quantum Yield and Free Rotor Effect | Zendy

M. S. A. AbdelMottaleb | Zendy

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Fluorescence Quantum Yield and Free Rotor Effect

Author(s) -

M. S. A. AbdelMottaleb

Publication year - 1983

Publication title -

laser chemistry

Language(s) - English

Resource type - Journals

eISSN - 1026-8014

pISSN - 0278-6273

DOI - 10.1155/lc.4.305

Subject(s) - quantum yield , fluorescence , chemistry , yield (engineering) , viscosity , reaction rate constant , picosecond , analytical chemistry (journal) , molecule , thermodynamics , chromatography , kinetics , physics , optics , organic chemistry , laser , quantum mechanics

It was found that the weakly fluorescent trans-2(4′-N,N-dimethylaminostyryl)- pyridinium betaine dyestuff (1) becomes efficiently fluorescent in very viscous media. The fluorescence quantum yield (φF) for dyestuff (1) approaches unity in ethanol–ether (1 : 1) glass at 98 K. Moreover, the fluorescence wave-length is blue shifted (1874 cm−1) when the temperature is lowered to 98 K. The results are rationalized as being due to solvent viscosity dependent rate constant for a radiationless internal conversion process, involving rotation of the different parts of the molecule, a free rotor effect. The rate of internal rotation was estimated to be 3.4 × 1011 s−1. The results suggest that this molecule can be used as a fluorescent probe to study microscopic structural changes in surrounding media occurring on the picosecond time scale.

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