Lanthanide Coordination Polymers and MOFs based on the Dicyanodihydridoborate Anion

New lanthanide cyanoborates were synthesized from anhydrous lanthanide chlorides and the acid H[BH2(CN)(2)] in either acetonitrile or pyridine. Reactions in acetonitrile lead to three-dimensional, anionic metal-organic frameworks (MOFs) (3)(infinity)[Ln(2){BH2(CN)(2)}(9)]center dot[Ln(CH3CN)(9)] (Ln = Ce, Eu, Tb) which incorporate complex cations [Ln(CH3CN)(9)](3+) in the pores of the framework for charge compensation. In contrast, the reactions in pyridine result in the formation of one-dimensional coordination polymers (1)(infinity)[H(py)(2)][LnCl(2){BH2(CN)(2)}(2)(py)(2)]center dot 0.5 py (Ln = Ce, Pr, py = pyridine) with [H(py)(2)](+) as counter ions for the anionic strand structure. The products show intense photoluminescence, for Ce3+ based on 5d-4f transitions in the blue spectral region, whereas the Eu3+ and Tb3+ compounds exhibit characteristic photoluminescence based on 4f-4f transitions of the respective lanthanide ions. The observed photoluminescence is mainly attributed to a direct excitation of the lanthanide ions and sensitization of the lanthanide ions by the [BH2(CN)(2)](-) anions. These results mark the utilized borate anions as versatile building block for new coordination compounds.