Hierarchical Self-Assembly of Pyrene-Linked Cyclodextrin and Adamantane-Linked Naphthalene Diimide System: A Case of Inclusion-Binding-Assisted Charge-Transfer Interaction

Abstract

Mixed stack charge transfer complexation between pyrene donor linked to β‐cyclodextrin and naphthalene diimide acceptor linked to adamantane, where the charge transfer interaction is augmented by inclusion binding of the adamantane moiety in β‐cyclodextrin, is studied. The association constant for the charge transfer complexation was 3.64 × 107 M−1, which is the highest value reported so far for any charge transfer complex. Complex formation was probed using 1H NMR, isothermal titration calorimetry, and circular dichroism studies. The results suggested that within the charge transfer complex the donor and acceptor exist as alternating units at an inter‐planar distance of 3.7 Å with a dihedral angle > 50° between them with each donor‐acceptor pair rotated slightly with respect to the preceding and succeeding pairs. The charge transfer complex undergo hierarchical self‐assembly to give twisted nanofibers as confirmed by Atomic force microscopic and Transmission electron microscopic studies. The excited state relaxation process in the charge transfer complex was investigated by femtosecond time‐resolved pump‐probe spectroscopy.