Transformation of [EMIm][BPB] into a Cationic Luminescent Ln ‐Coordination Polymer with the Bis(phthalato)borate Anion

Starting from phthalic acid and Na[BH 4 ], the low‐melting salt [EMIm + ][BPB] [EMIm + = 1‐ethyl‐3‐methylimidazolium; BPB – = bis(phthalato)borate] was synthesized and further reacted with Tb(NO 3 ) 3 · 6H 2 O to yield the one‐dimensional coordination polymer 1 ∞ [Tb( o ‐HBDC)(H 2 O) 6 ][BPB] 2 . Product formation is a result of the formation of the ortho ‐phthalato mono acid ( o ‐HBDC) from [BPB] – anions in the process and leads to linkage of adjacent Tb 3+ ions resulting in the cationic strand 1 ∞ [Tb( o ‐HBDC)] 2+ . The cationic charge of the coordination polymer is compensated by the [BPB] – anions in the crystal structure. Furthermore, the one‐dimensional coordination polymer 1 ∞ [Tb( o ‐HBDC)(H 2 O) 6 ][BPB] 2 shows characteristic luminescence based on the 4f–4f transitions of the Tb 3+ ions upon excitation with UV light.