Novel pyrazole-based carboxylate ligand as a building block for assembling lanthanides in luminescent 2D and 3D MOFs

New pyrazole-based carboxylic ligand 1-(carboxymethyl)-1H-pyrazole-3,5-dicarboxylic acid (H3L) as well as its lanthanide complexes [LnL(H2O)2]n, Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8) and [LnL(H2O)]n, Ln = Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14) have been prepared and studied. Compounds 1–8 represent a 3D polymer structure while 9–14 are 2D-polymers. Lanthanide-centered luminescence of compounds 4–9 is studied in detail. It is shown that high energy triplet level of H3L ligand (27100 cm−1) is able to sensitize not only the yellow-green luminescence of Tb3+ and Dy3+ ions, but also the red-orange luminescence of Sm3+ and Eu3+. NIR-luminescence of the neodymium complex 4 is possible upon direct excitation through the f-f transition of the Nd3+ ion.