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 1H- and 13C-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.