The kinetic behavior of the halato telechelic polymer (N,lV-dimethyl-.ÍV-[3-( l-pyrenyl)propyl]ammonio)trifluoromethanesnlfonate-end-capped poly(tetrahydrofuran) (POLYPROBE) in tetrahydrofuran is investigated by global compartmental analysis of the fluorescence decay surface. At low POLYPROBE concentrations the emission decays monoexponentially. When an analogous end-capped halato telechelic polymer without the pyrene chromophore ((Ñ,A,A-triethylammonio)trifluoromethanesulfonate-end-capped poly(tetrahydrofuran), POLYSALT) is added to solutions containing a low POLYPROBE concentration, the emission can be fitted by a biexponential decay function. From these observations it is concluded that the second excited-state species in the POLYPROBE-POLYSALT system is POLYPROBE involved in ion aggregation due to dipole-dipole or ion-dipole interaction. At higher POLYPROBE concentrations, without added POLYSALT, a triexponential decay function is needed to describe the emission. The third excited-state species is a POLYPROBE excimer, which can be formed via two pathways: either intermolecularly when a locally excited POLYPROBE encounters a ground-state POLYPROBE or intramolecularly when an aggregate of two POLYPROBE molecules rearranges. From the global compartmental analysis in which the value of one of the rate constants is scanned, it is found that the bimolecular processes are slowed down by the presence of the polymer chain, while intramolecular rearrangements are not affected.

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The previously presented bicompartmental models for intramolecular excited-state systems with added quencher [Boens et al. J. Phys. Chem. 1993, 97, 799 and Van Dommelen et al. J. Phys. Chem. 1993, 97, 117381 are experimentally investigated by time-resolved fluorescence measurements. The emission of the bichromophore bis(2-pyrenecarboxylic acid) 1,6-hexanediyl ester was studied in the absence and presence of iodomethane as a fluorescence quencher. Two different approaches are examined: one where no information is known beforehand and another where the time-resolved emission from the model compound hexyl 2-pyrenecarboxylate was used in the fittings. In the first approach, it was possible to obtain upper and lower limits for the rate constants hl, k21, h2, and kl2 (see Scheme 1) by analyzing at different preset values of the rate constant kol. For the other approach, the parameter values of h l and k~l were defined by linking these parameters with the corresponding rate constants of the model compound, whose quenched decays were included in the data analysis. For the calculations of the species-associated emission spectra (SAEMS) two different strategies were followed in the data analysis: one where no information from the model compound steady-state fluorescence spectra was included and one which made use of such information. SAEMS were obtained for both strategies, but inclusion of the steady-state fluorescence spectra information leads to better defined SAEMS for the locally excited state and excimer emissions.

This paper presents a study analyzing the conditions for the recovery of the rate constants and the spectral parameters from the fluorescence decay surface due to three-state excited-state processes. The studied system models a situation when, in addition to a fluorescence indicator which undergoes an excited-state reaction with a co-reactant, a fluorescent impurity is present. It is demonstrated theoretically that, if the fluorescence decay surface contains traces measured in the absence of co-reactant and additionally at two nonzero coreactant concentrations, all five rate constants can always be recovered. In some cases the measurement in the absence of co-reactant is not necessary. If the fluorescence decay surface is collected at three different emission wavelengths and two co-reactant concentrations, the ratios of the absorbances of the free and bound form of the fluorescent indicator can be determined. If two different emission wavelengths are used in combination with three excitation wavelengths (or three co-reactant concentrations), the ratios of the emission weighting factors of the free and bound form of the fluorescent indicator can be obtained. Under both previous conditions no spectral information about the fluorescent impurity can be acquired. The ground-state dissociation constant can be determined from the fluorescence decay traces excited at an isosbestic point.

Excimer formation in diastereoisomers of 2,4-diphenylpentane, base units of polystyrene, was investigated by using stationary and nonstationary techniques in isooctane. The rate constants of excimer formation of the meso and racemic isomers were compared and related to the conformational distribution within each configuration.