Molecular Fluoride-Bridged 3d-4f Complexes and Their Magnetic Properties

Fluoride-bridged systems benefit from the redox- and spectroscopic innocence of fluoride, which facilitates spectroscopic characterization and elucidation of their electronic structures. Although fluorine is often thought of as the "nonstick" element par excellence, fluoride-bridging can be utilized efficiently in tailored synthesis of polynuclear complexes and extended structures. In particular, the strong affinity of the lanthanides for fluoride makes it a good choice for directed synthesis of mixed lanthanide-transition metal complexes. Despite the competition from formation of lanthanide trifluorides with very high lattice enthalpies, building block approaches are not limited to robust systems and use of labile transition metal fluoride complexes has met with unexpected success. The physical properties of fluoride-bridged 3d-4f systems are crucially dependent on coordination geometries, which can be controlled to a fair extent via the geometric preferences of fluoride as the bridging entity.