Diversity of lanthanide(iii)-2,5-dihydroxy-1,4-benzenedicarboxylate extended frameworks: syntheses, structures, and magnetic properties

Abstract

Six lanthanide(III)-2,5-dihydroxy-1,4-benzenedicarboxylate frameworks, namely, [Ln(H₂-DHBDC)_1.5(H₂O)₂]_n (Ln = La (1) and Pr (2); H₄-DHBDC = 2,5-dihydroxy-1,4-benzenedicarboxylic acid), {[Nd(H₂-DHBDC)_1.5(H₂O)₃](H₂O)}_n (3), {[Eu(H₂-DHBDC)(NO₃)(H₂O)₄](H₂O)₂}_n (4), and {[Ln₂(H₂-DHBDC)₂(DHBDC)_0.5(H₂O)₃](H₂O)₄}_n (Ln = Gd (5) and Dy (6)), with four different structural types ranging from 1D chain, 2D layer to 3D networks have been synthesized and structurally characterized. Compounds La (1) and Pr (2) are isomorphous and exhibit 3D frameworks with the unique 1D tubular channels. Compounds Nd (3) and Eu (4) are 2D layer and 1D zigzag chain, respectively, which are further extended to 3D supramolecular frameworks through extensive hydrogen bonds. Isomorphous compounds of Gd (5) and Dy (6) are 3D frameworks constructed from secondary infinite rod-shaped metal–carboxylate/hydroxyl building blocks. While the hydroxyl groups as secondary functional groups in the 1D chain of Eu (4) and 2D layer of Nd (3) are not bonded to the lanthanide centers, the hydroxyl groups in the 3D frameworks of La (1), Pr (2), Gd (5), and Dy (6) participate in coordinating to lanthanide centers and thus modify the structural types of theses compounds. The magnetic data of compounds Pr (2), Nd (3), Gd (5), and Dy (6) have been investigated in detail. In addition, elemental analysis, IR spectra, powder X-ray diffraction (PXRD) patterns and thermogravimetric analysis of these compounds are described.