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Electronic absorption and fluorescence spectra based on transmission measurements of thin layers obtained from new perylene−zeolite L composites and new dye1,dye2−zeolite L sandwich composites, the latter acting as antenna systems, have been investigated and analyzed. The influence of extra-and intraparticle self-absorption on the spectral shape and fluorescence quantum yield is discussed in detail. Due to its intraparticle origin, self-absorption and re-emission can often not be avoided in organized systems such as dye−zeolite L composites where a high density of chromophores is a prerequisite for obtaining the desired photophysical properties. We show, however, that it can be avoided or at least minimized by preparing dye1,dye2−zeolite L sandwich composites where donors are present in a much larger amount than the acceptors because they act as antenna systems. ■ INTRODUCTIONComposites synthesized by embedding molecules, complexes, and clusters into the one-dimensional channels of zeolite L (ZL) 1,2 have recently experienced increasing interest from scientists engaged in different fields, ranging from very stable nontoxic pigments to novel optical materials with a large variety of different properties to promising objects for utilization in analytics, biology, diagnostics and drug delivery. This trend is exemplified by publications that appeared in 2013. 3−16 Electronic absorption and luminescence spectroscopy are important tools for characterizing the host−guest composites, and luminescence is often one of their key properties. Confocal luminescence microscopy on individual crystals has successfully been used and has contributed much to our current understanding of various dye−ZL properties. 17−23 It is very often desirable to measure absorption and luminescence spectra of an ensemble in order to unambiguously interpret the observations and sometimes to derive luminescence quantum yields. Diffuse reflectance spectroscopy has frequently been used in the case for which this sophisticated instrumentation has been developed. 10,24 Advancing dye−ZL research requires measurements that not only yield spectra and quantum yields as numbers but also provide information useful for understanding the mechanisms behind the observed phenomena. A prerequisite for these are high quality absorption and luminescence spectra where the band shapes can be interpreted unambiguously. This is best guaranteed if high quality transmission spectra are available. We have therefore successfully applied refractive index matching techniques in order to reduce or in favorable cases eliminate light scattering. We have used dispersions in liquid solvents or polymers as matrixes for dye−ZL composites, where sometimes a surface modification of the ZL crystals was required.25−27 More recently, a method for the preparation of thin oil−glass sandwiches (OGS) from dye−ZL composites has been employed. 15,20 This technique has proven to be very convenient and allows differentiating between mechanisms that affect the shape of the absorptio...

Sequential insertion of different dyes into the 1D channels of zeolite L (ZL) leads to supramolecular sandwich structures and allows the formation of sophisticated antenna composites for light harvesting, transport, and trapping. The synthesis and properties of dye molecules, host materials, composites, and composites embedded in polymer matrices, including two-and three-color antenna systems, are described. Perylene diimide (PDI) dyes are an important class of chromophores and are of great interest for the synthesis of artificial antenna systems. They are especially well suited to advancing our understanding of the structure-transport relationship in ZL because their core fits tightly through the 12-ring channel opening. The substituents at both ends of the PDIs can be varied to a large extent without influencing their electronic absorption and fluorescence spectra. The intercalation/insertion of 17 PDIs, 2 terrylenes, and 1 quaterrylene into ZL are compared and their interactions with the inner surface of the ZL nanochannels discussed. ZL crystals of about 500 nm in size have been used because they meet the criteria that must be respected for the preparation of antenna composites for light harvesting, transport, and trapping. The photostability of dyes is considerably improved by inserting them into the ZL channels because the guests are protected by being confined. Plugging the channel entrances, so that the guests cannot escape into the environment is a prerequisite for achieving long-term stability of composites embedded in an organic matrix. Successful methods to achieve this goal are described. Finally, the embedding of dye-ZL composites in polymer matrices, while maintaining optical transparency, is reported. These results facilitate the rational design of advanced dye-zeolite composite materials and provide powerful tools for further developing and understanding artificial antenna systems, which are among the most fascinating subjects of current photochemistry and photophysics.

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A new practical method for the synthesis of tetracyclic pyrido[2′,1′:2,3]imidazo[5,1‐a]isoquinolinium compounds by a Yb(OTf)3/AgOTf‐catalyzed (Tf = triflate) three‐component domino reaction was developed. Significantly, the strategy presents a straightforward and efficient approach to constructing a series of compounds with potent cytotoxic activities.