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The (aR,aR,uR) and (uS,aS,aS) enantiomers of a chiral macrobicyclic ligand with a bicapped tris(binaphtho1) structure were synthesized. Complexation of galliKeywords um(III), chromium(ni) and iron(1n) centres in the chiral cavities of these two ligands chirality * coordination modesyielded exclusively one octahedral configuration in each case: the (aR,aR,aR) enanmacrocyclic ligands -octahedral comtiomer gave a A complex and the (uS,aS,aS) enantiomer a A complex. These assignplexes * supramolecular chemistry ments were established by CD spectroscopy for chromium and iron centres and by molecular modelling.

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Study of the photodegradation and the "colorability" of nonazaheterocyclic spiropyrans by repeated flashes showed the influence OF different effects involving the heteroatom, the substituent and the concentration. Substituents in 3 ' , 6 ' and 8 ' positions of the benzopyran part are very important for stabilization of the colored open form (thermal bleaching kinetic constant), for "colorability" and photodegradaton. The primary photochemical process is essentially localized in the benzopyran part but in the photomerocyanine isomer there is interaction between the two moieties. The "colorability" and the photodegradation vary inversely with concentration. All compounds present generally a bad "colorability" but also a sufficient light-stability at high concentrations. A general scheme for the photocoloration and photodegradation of spiropyrans is also proposed.