Nitroxide free radicals are widely used as spin carriers for the design of Molecular Magnetic Materials. Indeed, they are among the only few purely organic materials ordering ferromagnetically and their coordination properties allow to built molecular structures where the nature of the interaction between individual spin carriers can be controlled. In this contribution we describe new nitroxide ligands which have been designed for obtaining clusters and extended structures of exchange coupled species. In particular, are described copper(II) clusters which undergo a structural change with the temperature and exhibit a spin transition like behavior and complexes of new chelating nitroxides which allow the use of poorly acidic metal centers to design extended molecular structures.