Aggregation of organic dyes often has consequences on their spectroscopic properties in materials. Here, we study a new sterically hindered boron-dipyrromethene (BODIPY), with adamantyl moieties grafted for the first time on the BODIPY core. Its aggregation behavior was investigated in poly(methyl methacrylate) (PMMA) and on drop-casted films by monitoring absorption, fluorescence emission, relative quantum yield (ΦFluo,Rel), lifetime and time-resolved anisotropy. Aggregates only appear from 0.067 mol·L–1. A multicomponent analysis demonstrated that the aggregation process can be described by three distinguishable components which correspond to a monomer species (M) and J and H aggregates. The results also indicated a concentration frontier: when the dye concentration increased up to 0.29 mol·L–1, the concentration of M decreased in favor of the aggregates. ΦFluo,Rel is yet only divided by 5 compared to the dye in solution. Above 0.29 mol·L–1, an equilibrium between M and the J aggregates is established, showing meanwhile a steady ΦFluo,Rel. The J aggregates are found to be dimers, whereas the aggregation number is varying for the H aggregates. Analysis of fluorescence and anisotropy decays showed that the excitation energy was transferred from M to the J dimers, and very probably trapped by H aggregates.

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The polarization states of lasers are crucial issues both for practical applications and fundamental research. In general, they depend in a combined manner on the properties of the gain material and on the structure of the electromagnetic modes. In this paper, we address this issue in the case of solid-state organic lasers, a technology which enables to vary independently gain and mode properties. Different kinds of resonators are investigated: in-plane micro-resonators with FabryPerot, square, pentagon, stadium, disk, and kite shapes, and external vertical resonators. The degree of polarization P is measured in each case. It is shown that although TE modes prevail generally (P >0), kite-shaped micro-laser generates negative values for P , i.e. a flip of the dominant polarization which becomes mostly TM polarized. In general, we demonstrate that both the pump polarization and the resonator geometry can be used to tailor the polarization of organic lasers. With this aim in view, we, at last, investigate two other degrees of freedom, namely upon using resonant energy transfer (RET) and upon pumping the laser dye to a higher excited state. We then demonstrate that significantly lower P factors can be obtained.

BODIPYrrole: A general strategy for the design of novel BODIPY fluorophores based on pyrroles with polycondensed aromatic and metallocene substituents has been developed. The strategy involves the acylation of the condensed substituent and treatment of the acylated derivative (as oxime) with acetylene in MOH/DMSO (M = alkali metal) to give pyrroles that were then used for assembly of the BODIPY fluorophores (see scheme).