Perylene diimide – POSS dyes as a way to inhibit aggregation caused quenching

In recent years there has been an extensive research on the development of efficient solid-state emissive organic materials for organic optoelectronic devices, such as light-emitting diodes, organic field-effect transistors, solid-state lasers and fluorescent sensors. However, most organic chromophores are non-luminescent in the solid state, even if they are highly emissive in solution, owing to the quenching caused by intermolecular interactions such as aggregation caused by π–π stacking [1]. This is the case of perylene tetracarboxylic acid diimides (PDI), an important class of industrial pigments, which have been recently investigated for their interesting properties such as near-unity fluorescence quantum yields in solution, high photochemical stability, and strong electron-accepting character, that allow PDIs to be used in many electronic and optical applications [2]. We report on the preparation of PDI derivatives anchored to inorganic scaffolds such as Polyhedral Oligomeric Silsesquioxanes (POSS) with the aim to suppress the quenching which occurs in the solid state due to π–π stacking of this kind of emitting chromophores. The new PDI-POSS compounds here presented show in solution the typical absorption and emission features of the monomeric perylene unit, with a quantum efficiency close to unity, while in the solid state (both as spin-coated films and powders) the fluorescence quantum yield is positively affected by the presence of the POSS cage, with a quantum efficiency about 6 times that of the corresponding perylene tetracarboxylic bisimide in the solid state. [1] M. Shimizu, T. Hiyama, Chem. Asian J. 5, 2010, 1516. [2] C. Huang, S. Barlow, S.R. Marder, J. Org. Chem. 76, 2011, 2386.