70. Ion-Pairing Effects in the Self-Assembly of a Fluorescent Pseudorotaxane
    Miguel Clemente-León, Chiara Pasquini, Virginie Hebbe-Viton, Jérôme Lacour, Antonella Dalla Cort, Alberto Credi
    Eur. J. Org. Chem. 2006, 105-112

Herein we report on the self-assembly, in a low polarity solvent, of a pseudorotaxane species comprising binaphthyl-26-crown-8 (BN26C8) as the macrocyclic host and anthracenyl-benzylammonium as the threadlike positively charged guest (ABH⁺). Absorption and luminescence data reveal a very efficient energy transfer process occurring from the binaphthyl to the anthracene singlet excited states. The self-assembly is highly dependent on the nature of the counteranion confirming the crucial role played by it in the competition between the self-assembly process and the formation of ion pairs (ABH⁺X^–). This behavior can be readily evidenced in dilute solutions from the analysis of the luminescence properties of the system. The complexation of chloride, sulfate and hexafluorophosphate salts of ABH⁺ by racemic BN26C8 as well as the complexation of ABH⁺ salts of the chiral anion tris[tetrachlorobenzenediolato]phosphate(V) (TRISPHAT^–) by (+)BN26C8 are described. The efficiency in complexation follows the trend PF₆^– > TRISPHAT^– > Cl^–, SO₄^2–. The use of the chiral anion TRISPHAT allowed us to investigate the possibility of inducing stereoselective control on the formation of the interpenetrating assembly. Preliminary ¹H NMR spectroscopic evidence supports the fact that the chiral anion is paired to the supramolecular complex and that its configuration influences the recognition process.

DOI : 10.1002/ejoc.200500479 

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