4f-intermediate valence in an ytterbium-bipyridine coordination solid.

We report the first structurally characterised coordination solids based on decamethylytterbocene, using bipyridine linkers to form YbCp*2(bipy) and YbCp*2(Me2bipy). Analogous to their mononuclear cousins known for intermediate valence, spectroscopic evidence suggests that YbCp*2(bipy) features a multiconfigurational ground state, composed of a superposition of an open-shell ligand non-innocent 4f(π*) state and a closed-shell 4f state. Our findings mark a first step toward increasing electronic correlations in lanthanide-organic frameworks, with the aim of realising materials with coexisting electronic transport and emergent magnetic properties.