Single-atom substitution enables supramolecular diversity from dipeptide building blocks

Dipeptides are popular building blocks for supramolecular gels that do not persist in the environment and may find various applications. In this work, we show that a simple substitution on the aromatic side-chain of phenylalanine with either fluorine or iodine enables supramolecular diversity upon self-assembly at neutral pH, leading to hydrogels or crystals. Each building block is characterized by H-1- and C-13-NMR spectroscopy, LC-MS, circular dichroism, and molecular models. The supramolecular behaviour is monitored with a variety of techniques, including circular dichroism, oscillatory rheology, transmission electron microscopy, attenuated total reflectance Fourier-transformed infrared spectroscopy, visible Raman spectroscopy, synchrotron-radiation single-crystal X-ray diffraction and UV Resonance Raman spectroscopy, allowing key differences to be pinpointed amongst the halogenated analogues.

Automated summary

Dipeptides are versatile building blocks for supramolecular gels that can be used in various applications. This study demonstrates that by substituting the aromatic side-chain of phenylalanine with fluorine or iodine, supramolecular diversity can be achieved through self-assembly at neutral pH, resulting in hydrogels or crystals. The supramolecular behavior is characterized using a range of techniques, revealing key differences among the halogenated analogues.