Caro-Cryptands: Tris-carotenoid macrobicyclic ligands–synthesis,crystal structure,and dinuclear copper(I) complexes

The tris-carotenoid macrobicycles 1 and 2 were obtained in good yields in a one-step macrobicyclisation condensation between the tripode N(CH₂CH₂NH₂)₃ and the polyolefinic dialdehydes 5 and 6 . They form dinuclear cryptates by complexation of two Cu^I ions. The crystal structure of the tris-carotenoid compound 2 confirms that it contains three parallel polyolefinic strands. These substances may formally be considered as prototypes of molecular ‘cables’ formed by three electron-conducting molecular wires.