Single-atom substitution enables supramolecular diversity from dipeptide building blocks

In this work, we show that a simple substitution on the aromatic sidechain of phenylalanine with either fluorine or iodine enables supramolecular diversity upon selfassembly at neutral pH, leading to hydrogels or crystals.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.