There is a demand for new methods of protecting organic dyes from aggregation effects and photochemical degradation. The purpose of this microreview is to summarize the recent attempts to improve the properties of dyes by molecular encapsulation. Organic dyes have been encapsulated inside inorganic matrices such as molecular sieves, and molecular containers such as cyclodextrins, cucurbiturils, dendrimers, and self-assembled gels. Another strategy is perma-
IntroductionOrganic chromophores such as cyanines, squaraines, azo dyes and perylenediimide dyes are widely used as pigments in many commercial products. They are active ingredients in semiconducting materials, [1] textile products, [2] laser materials, [3] optical disks, [4] paints, [5] and probes for biological systems.[6] Modern research on organic dyes includes investigations of building blocks for conjugated polymers, hydrogen bonded assemblies, chromogenic sensors, molecular shuttles, solar energy cells, photonics and various approaches to photodynamic therapy. [7][8][9][10][11] A common limitation with organic dyes, especially those with long-wavelength absorption bands, is their susceptibility to chemical and photochemical degradation. The reason for the enhanced reactivity is the inherently small HOMO-LUMO energy gap, which means that the dyes are potentially reactive with both nucleophiles and electrophiles. Another potential drawback with organic dyes is their tendency to aggregate, which induces multichromophoric interactions that alter the color quality and quench the photoluminescence. In principle, these problems can be attenuated by supramolecular encapsulation strategies that isolate the individual dye molecules and prevent self-aggregation or similar interactions with the chemical environment. The purpose of this microreview is to summarize the recent literature on meth- Germany, 2005) ods to improve the properties of organic dyes by molecular encapsulation. The focus is on relatively "robust" molecular containers and does not include "soft" assemblies like micelles, emulsions or vesicles.