Multifunctional Single-Molecule Magnets with Slow Relaxation of Magnetization, Luminescence and Ferroelectricity—The Quest for Cross-Coupling Between Properties

Coordination chemistry of lanthanide ions allows the tailored design of multifunctional molecule-based materials where the properties are gathered into a single molecular system. Yet, taking advantage of the multifunctional character in future applications will imply the presence of a strong interaction between the properties.<br/>In this regard, Single-molecule Magnets (SMM) belong to a specific class of magnetic materials affording a magnetic bistability at the molecular scale. By using specific molecular building blocks, we show that these systems could also exhibit additional properties such as luminescence, optical activity and ferroelectricity. Remarkably, we demonstrate that such molecular systems could go beyond the simple superposition of the properties and exhibit cross-coupling effects that could be used in potential applications.<br/>Firstly, we will focus on the cross-coupling between luminescence and magnetic field to design dual sensors affording the dual and synchronous detection of the temperature and magnetic field in large ranges (10-180 K and up to 45 Teslas). Secondly, we will describe the design of high temperature ferroelectric materials having a high degree of functionality, combining Single-Molecule Magnet behavior, optical activity and lanthanide luminescence. Remarkably, these molecular systems could behave as ferroelectrics up to a temperature above 180 K of the Curie temperature of BaTiO₃, making it the highest temperature working molecular ferroelectric yet reported. Besides, we demonstrated the presence of a room temperature strong magnetoelectric coupling, resulting from the association between ferroelectricity and magnetostriction (deformation of the crystal structure under the effect of a magnetic field).