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 (H 3 L) has been prepared. • Two new families of lanthanide complexes [LnL(H 2 O) 2 ] n , Ln = La-Tb and [LnL(H 2 O)] n , Ln = Dy-Lu has been prepared and studied. • It was shown that the ligand H 3 L is able to sensitize the lanthanide luminescence emitting in VIS-region, especially Tb 3+ . New pyrazole-based carboxylic ligand 1-(carboxymethyl)- 1H- pyrazole-3,5-dicarboxylic acid ( H 3 L ) as well as its lanthanide complexes [LnL(H 2 O) 2 ] n , Ln = La ( 1 ), Ce ( 2 ), Pr ( 3 ), Nd ( 4 ), Sm ( 5 ), Eu ( 6 ), Gd ( 7 ), Tb ( 8 ) and [LnL(H 2 O)] 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 H 3 L ligand (27100 cm −1 ) is able to sensitize not only the yellow-green luminescence of Tb 3+ and Dy 3+ ions, but also the red-orange luminescence of Sm 3+ and Eu 3+ . NIR-luminescence of the neodymium complex 4 is possible upon direct excitation through the f-f transition of the Nd 3+ ion.