Helical assembly induced by hydrogen bonding from chiral carboxylic acids based on perylene bisimides.

The control over self-assembly behavior becomes absolutely critical because it is dependent on the orientation and morphology. The motivation is focused on borrowing the help of O-H···O hydrogen bonding interactions to realize the control in chiral self-assembly. A series of perylene bisimide (PBI) dyes 3a-3d bearing chiral amino acid derivatives on the imide N atoms and four phenoxy-type substituents at the bay positions of the perylene core were synthesized. Optical properties and aggregation behavior of PBIs were investigated by absorption, fluorescence, circular dichroism (CD), and (1)H NMR spectroscopy. Except for the chiral ester 3c and achiral 3d, chiral dyes 3a and 3b show bisignated CD signals, indicating that the chiral carboxylic acid-functionalized PBI systems are found to be spontaneously self-assembled into supramolecular helices via intermolecular hydrogen bonding rather than π-π stacking. Furthermore, the chirality-controlled helical superstructures are strongly dependent on several factors, such as solvent polarity, concentration, and temperature. The supramolecular helical chirality can be well-controlled by the chiral amino acid residues in the PBI system; that is, the assembled clockwise (plus, P) or anticlockwise (minus, M) helices can be induced by L- or D-isomers, respectively.