Modulation of Small Molecule Induced Architecture of Cyclodextrin Aggregation by Guest Structure and Host Size

A small molecule based on bisphenylethynyl amide meta linked to 2,6-pyridine can induce cyclodextrin (CD) aggregation through a possible 1:3 guest–host motif. Most of the small molecules induce CD nanotubular bundles principally through 1:2 guest–host unit capsules and aggregate through hydrogen bonding among the hydroxyl groups present on the rims of the CD molecules. The N,N-dimethyl aminopropyl carboxamide side chain and the central pyridine ring of 6-bromo-2-phenylethylaminopyridine (BPEAP) induces nanotubular bundles with α-CD and laminar bundles with β- and γ-CDs, which, as a consequence, may result in formation of pores in the aggregates that can find wide applications in biological storage machinery. The stoichiometry of the ingredients of the unit capsules has been evidenced by Job’s plot. The size-dependent suprastructures induced by BPEAP have been studied by steady state and time-resolved fluorescence spectroscopy and atomic force microscopy.