Transition metal impurities in fluorides: Role of electronic structure of fluorine on spectroscopic properties

► Transition metal complexes with fluorine as ligand. ► Chemical bonding and spectroscopic parameters. ► 10Dq depends on the metal ligand distance. Racah parameters are little sensitive. ► 10Dq does not depend on the global covalency but on the tiny 3d-2s hybridization. ► Relation between optical and EPR parameters.