Interaction between light and matter is of fundamental importance in physical, chemical and biological sciences, because of a variety of applications, for instance in optical information technology devices, in lasers and lighting, and in solar-energy harvesting. Coordination chemistry provides a convenient tool to prepare solids with tailored optical properties. However, the actual use of such materials in devices requires processing of the compounds into well-defined and often size-reduced particles. This project aims at the preparation of nano-objects, starting from oxalate-based networks, well known for their optical and magnetic properties. For example, [M(bpy)3][NaCr(ox)3] 3D networks are known to present a photo-induced energy migration process within the CrIII cations over large distances (up to 100 nm when M = RuII) or an unusual spin crossover behaviour when M = CoII.The first step will be the adaptation of nanochemistry methods (reverse-micelles technique and others…) to this family of compounds, in order to obtain size-controlled particles and, in a second step, functionalized nanoparticles and core-shell nano-objects. With [Ru(bpy)3][NaCr(ox)3] nanoparticles, the influence of size reduction on the energy migration process will be investigated. Functionalized nano-objects, either by grafting complexes on the surface or by epitaxial growth of a different oxalate network shell, will then be used to study the energy transfer from the core particle to the surrounding. Finally, [Co(bpy)3][LiCr(ox)3] will be prepared to study the size reduction effect on the spin crossover process of the [Co(bpy)3]2+ cations. Thus, this project is expected to give a better insight on the effect of size-reduction on the photo-induced energy migration, energy transfer and spin crossover processes.