Azabuckybowl-based molecular pincers of fullerenes: A noncovalent intermolecular D-A-D system

Abstract

The pincer-shaped “bucky-catcher” strategy with the aid of two embedded nitrogen atoms on the buckybowl subunits has been successful used in enhancing the association with fullerene C60 and C70. The linker group between two azabuckybowls plays a vital role for the selective recognitions of C60 and C70. In this work, besides having been experimentally studied -CH=CH- and –NH- linkers, several other linkers, including –O-, -S-, -CH2- and group-free are considered for the N-embedded buckybowl molecular pincers as receptors for fullerene C60 and C70 by using DFT calculations. The designed receptors can exist in trans and cis configurations. Most of the trans forms of free receptors (which mismatch with fullerenes) can spontaneously recognize and bind C60 and C70 with large binding energies (210– 235 kJ·mol−1) by gradually turning their scissors-shaped configurations to the pincer-shaped ones. For each receptor, the binding energy for C70 is greater than that for C60. The donor–acceptor–donor (D–A–D) systems can be constructed with these receptors upon binding with C60 or C70, in which the two-photon absorption (TPA) cross-section would occur via photo-excitation.