All-organic nanostructured host-guest systems, based on dyes inserted in the nanochannels of perhydrotriphenylene (PHTP) and deoxycholic acid (DCA), show enhanced fluorescence properties with quantum yields even higher than those of the dyes in solution, thanks to the high concentration of emissive molecules with controlled spatial and geometrical organization that prevents aggregation quenching. Both host molecules crystallize, growing with the long axis oriented along the direction of the nanochannels where the linear-chain dyes are inserted, to yield crystals emitting well-polarized light. For the DCA-based host-guests, homogeneous thin films suitable for several applications are obtained. Colour emission in such films can be tuned by co-inclusion of two or three dyes due to resonant energy-transfer processes. We show that films obtained by low-cost techniques, such as solution casting and spin-coating, convert UV light into visible light with an efficiency much higher than that of the standard polymeric blends.

An analysis of propylene polymerization in the presence of metallocene complexes was carried out on the basis of the alternating mechanism and formulated in terms of fundamental stereochemistry. A statistical approach allowed the calculation of pentad distribution for polypropylenes produced in the presence of isospecific, syndiospecific, and hemiisospecific catalysts. Comparison with experimental data published for hemiisotactic polypropylene confirmed the validity of the alternating mechanism but showed also the presence of successive additions at the same catalyst face.The structure of hemiisotactic polypropylene (hit-PP) was envisaged long ago in the course of our studies on the solid-state polymerization of substituted butadienes. The first example of hit-PP was obtained in our laboratory in 1982 by a two-step synthesis starting from trans-2-

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Dyes inserted into the parallel nanochannels of a fully organic crystal show efficient light conversion over a wide visible spectral region, with 100% conversion from UV to blue light. The Figure shows crystals containing either two (bottom) or three (top) dyes under U v illumination, and a top view of the structure of the dyes inserted into nanochannels

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