Variety of steady and excited state interactions in BODIPY aggregates: photophysics in antisolvent systems and floating layers

Associative behavior of geometrically anisotropic meso-(4-octadecyloxy-phenyl)-boron-dipyrrin (BODIPY) studied spectroscopically in binary solvent mixtures and upon compression in Langmuir floating layers. Different steady and excited state species were found upon monolayer compression and facilitated aggregation in water / acetonitrile systems. This discrepancy points to a big concern in possibility of commonly applied generalizations across different aggregating systems. Broad range of decay fitting models were examined to reveal their benefits and pitfalls specific to examination of dye aggregates. Radiative constant gamma-distribution approach and free form fluorescence lifetime distribution with maximum entropy method (MEM) outperformed multiple common techniques for analysis of complex fluorescence decays. MEM could be recommended for analysis of systems where complicated lifetime distributions appear over time or upon external stimuli. Findings and protocols could be utilized as tools in studies of steady and excited-state photophysics of BODIPY aggregates.