Coordination polymers built up from an s-tetrazine derived ligand and rare-earth ions: from a sequential dimensional expansion to organic-inorganic energy transfer.

Coordination polymers were prepared from a luminescent s-tetrazine ligand (OTz) and various rare-earth ions. Both the radii of the Ln ions and the synthetic conditions (especially pH) drive the formation of the product, and three crystalline phases were finally identified. Using a two-step process, it was possible to increase the dimensionality of one of these compounds from 1-D (MIL-165) to 2-D (MIL-166). The luminescence properties of these coordination polymers were studied. Whereas for Ln = La, Pr, Eu, Tb, the emission characteristic of the s-tetrazine core was observed, such emission was not detected for Ln = Nd, while the emission typical for the Nd ion was present, due to energy transfer from the tetrazine ligand to the Nd3+ ion.