Temperature Dependence of Fluorescence Lifetime Distributions in 1,3-Di(1-pyrenyl)propane with the Maximum Entropy Method.

The fluorescence decay of the monomer emission band of 1,3-di(1-pyrenyl)propane has been investigated at different temperatures in order to test models implying either the presence of three distinct species (one monomer and two excimers) or a more complex situation, giving rise to lifetime distributions. The decay curves were analyzed by free-floating discrete multiexponential functions (up to four exponentials) and as well s with the maximum entropy method. The latter uses a set of up to 200 exponential terms with fixed lifetimes and is capable of recovering distribution over a broad lifetime range. The result clearly indicate the presence of a distribution of conformers in the monomer state, which leads to a broad monomer lifetime distribution, the relative width of which is temperature dependent. This distribution of conformers also accounts for the inability to fit the high-precision monomer decays collected to high count level at higher temperatures with a three-exponential function.