Abstract
Dynamics of intramolecular electronic energy transfer in bichromophoric molecules, consisting of two coumarins linked by a variable number of methylene groups, is investigated by multifrequency phase-modulation fluorometry. From observation of the acceptor delayed emission, information on the rate of transfer can be obtained.
Highlights
Intramolecular electronic energy involving two chromophores separated by a molecular chain or frame is still receiving considerable attention because of its unplications tn numero~ fields: photophysi~al processes, biologrcal systems, dye lasers. wavelength shifters, etc
Pulse fluorometry has been currently used for this purpose btrt never phase fluorometry thanks to recent improvements based on multifrequency modulation of light and cross-correlation detection [d], phase fluorometry can provide information equivalent to that obtained with pulse fluorometry 15,6]_ In the present paper, we report the first investigatton of energy-transfer dynamics by phase fluorometry
Nevcrtheless, Information on transfer rate is contained in time-dependent acceptor fluorescence via donor excitation_For instance, picosecond pulse fluorometry can be usad for the dctermmation of the rise of the acceptor fluorescence following pulse excitation of the donor [7] _Alternately, as shown in this paper, phase fluoromctry experiments are based on the measurement of the phase shift between the acceptor fluorescence in the presence of transfer with respect to the acceptor fluorescence in the absence of transfer at various frequencies_This kind of experiment is reported in the present work using the above-depicted bichromophoric molecules
Summary
Intramolecular electronic energy involving two chromophores separated by a molecular chain or frame is still receiving considerable attention because of its unplications tn numero~ fields: photophysi~al processes, biologrcal systems, dye lasers. wavelength shifters, etc. Pulse fluorometry has been currently used for this purpose btrt never phase fluorometry thanks to recent improvements based on multifrequency modulation of light and cross-correlation detection [d] , phase fluorometry can provide information equivalent to that obtained with pulse fluorometry 15,6]_ In the present paper, we report the first investigatton of energy-transfer dynamics by phase fluorometry. Nevcrtheless, Information on transfer rate is contained in time-dependent acceptor fluorescence via donor excitation_ For instance, picosecond pulse fluorometry can be usad for the dctermmation of the rise of the acceptor fluorescence following pulse excitation of the donor [7] _Alternately, as shown in this paper, phase fluoromctry experiments are based on the measurement of the phase shift between the acceptor fluorescence in the presence of transfer with respect to the acceptor fluorescence in the absence of transfer at various frequencies_ This kind of experiment is reported in the present work using the above-depicted bichromophoric molecules. Data were analyzed for a single and double exponential decay using the KS lifetime analysis software_ analysis is based on a non-linear least-squares method described by Brandt [I 0] _ The equations used and the attainable resolving power have been reported elsewhere [5,6] _ Error analysis is obtained from the computation of the diagonal terms of the covarlance matrix of errors as reported by Brandt [101-
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