Merocyanine and Spiropyran Adsorption on Graphene

We have investigated the adsorption of spiropyran-based molecular switches on a graphene substrate using a combination of quantum-chemical and force-field-based calculations. Four different spiropyran molecules and their merocyanine isomers have been studied regarding the influence of different end groups on the surface adsorption and intermolecular configurations. Following the investigation of the adsorption behavior of single molecules, we expanded the study to the dimer formation of two identical molecules. This configuration is thought of as the precursor for substrate-wide film growth of the spiropyran-based molecular switch. The adsorption mechanisms and dimer formations can be understood due to an interplay of different parts of the molecules through van der Waals interactions and electrostatic forces from partial atomic charges of parts of the molecules. Furthermore, for each molecule, dimers based on different conformers of the merocyanine isomers could be identified.