The thesis describes at first a selection of the research work carried out between 2005 and 2022 on magnetic molecular materials. It is about the characteriza/on by magnetometry and by EPR spectroscopy of molecular and mono-ionic nanomagnets, spin transi/on compounds based on Fe(II), and electron-transfer compounds called also molecular analogues of Prussian blue (mPBAs). A more detailed description has been devoted to the switching process of mPBAs under external s/muli (T, P and light). The second part of the thesis describes the research projects axed on the piezo-induced magnetic switching of mPBAs.