Photoswitchable ligands as biological tools provide an opportunity to explore the kinetics and dynamics of the clinically relevant µ-opioid receptor. These ligands can potentially activate and deactivate the receptor when desired, using light. Spatial and temporal control of biological activity allows for application in a diverse range of biological investigations. Photoswitchable ligands have been developed in this work, modeled on the known agonist fentanyl, with the aim of expanding the current ‘toolbox’ of fentanyl photoswitchable ligands. In doing so, ligands have been developed that change geometry (isomerize) upon exposure to light, with varying photophysical and biochemical properties. This variation in properties may be valuable in further studying the functional significance of the µ-opioid receptor.