FLUO 3 |
| Fluorine, „the little atom that could“, in recent years has evoked numerous investigations in organic synthesis and crystal engineering. Intermolecular interactions of the type C-F…H, F…F and C-F… πF are frequently found and can have a decisive influence on the packing. Although coulombic interactions between fluorinated and nonfluorinated arenes lead to stacking in most cases, the packing energy of such crystals is nevertheless dominated by dispersion, whereas coulombic terms can allow particular motif formation. Generally, the synthesis of perfluorinated conjugated molecules such as 1,4-disubstituted benzenes and 4,4'-disubstituted stilbenes are of particular interest. In the case of donor and acceptor disubstituted tetrafluorobenzenes, an exceptionally high percentage of acentric structures were obtained. This feature seems not to extend into the stilbene analogues, were a study has revealed only centric structures. However, this class represents building blocks which allow to analyse the packing mode of e.g. F4- or F8-4,4'-disubstituted stilbenes, forming all kinds of interaction motifs along chains. Particularly of interest is the formation of compound-type systems in the solid state and solid solutions. In the case of building blocks acting as a host molecule for inclusion formation, triazines turned out to be of interest. Partial or perfluorination can significantly affect the channel-type inclusion behavior of triazines. Along such a study, the heteroatoms linking the triazine ring to the phenyl substituent were varied (O, S, NH). In all cases channel-type inclusions with solvent molecules were obtained. Most interestingly, the zeolite properties were investigated for the case of a number a mono- and difluorinated bromo-triazines. Here, empty channel structures with a van der Waals diameter of about 10.5 Å were thermally stable up to 110° C, to be compared with 70° C for the non-fluorinated bromo-triazine. Various large size guest molecules such as decamethyl-ferrocenes, fullerenes and bucky-ferrocenes were included into these channels. |
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Nanostructured Fluorocarbons: Smart Tectons for Self-Assembly
12:00 PM-5:05 PM, Sunday, August 19, 2007 BCEC -- 252B, Oral
Division of Fluorine Chemistry |