Self-Aggregation, Enhanced Guest-Binding Behavior, and Anion-Induced Agglutination of Cyclophane Dimers Linked with...

Cationic, anionic, and nonionic cyclophane dimers, 1a, 1b, and 1c, covalently linked with fluorescent perylene diimide were synthesized, respectively, as a host for aggregation-induced multivalent effects on guest-binding. These PDI-linked cyclophane dimers 1a and 1b, especially 1c, formed self-aggregates in H₂O-rich solvents through π-stacking interactions. Critical aggregation concentrations of 1a, 1b, and 1c in H₂O were 4.0 × 10^-6, 4.0 × 10^-6, and less than 0.1 × 10^-6 M, respectively. The self-aggregates of the PDI-linked cyclophane dimers in H₂O were several hundred nanometers in size by DLS and TEM measurements. In an aggregated state, 1a exhibited guest-binding abilities toward hydrophobic guests, such as 6-p-toluidinonaphthalene-2-sulfonate and 6-anilino-naphthalene-2-sulfonate. Moreover, anion-induced agglutination of 1a was observed upon the addition of phosphate ions, and its effectiveness was as follows: ATP > ADP > H₂P₂O₇^2- > AMP ≈ PO₄^3- > HPO₄^2- > H₂PO₄^-. The contribution of the adenine base of the nucleotides as a guest moiety used for effective agglutination was confirmed by ¹H NMR spectroscopy.