Expanding the Library: Twenty New Ln(III) Metal–Organic Frameworks, Including Two Isoreticular Pairs, from Dihaloterephthalic Acid

Abstract

Twenty new metal−organic frameworks (MOFs) were synthesized from 2,5-dihaloterephthalic acid ligands (DXTAH) and LnCl 3 •xH 2 O by varying the Ln(III) radius, DXTAH (X = Cl or Br), and reaction conditions. The compounds are grouped into seven families: {[Ln(DClTA) 1.5on the identity of the ligand, the role of solvents, and the supramolecular structure of the framework. Among the 20 MOFs, 19 feature pseudopaddlewheel [Ln 2 (COO) 6 ] SBUs, while one has a rod-like Ln−O−C SBU, and there are two pairs of isoreticular Ln-MOFs. DXTA displays eight coordination modes, three are new for Ln-dihaloterephthalate compounds, and one is being reported for the first time for Ln-haloterephthalates. Coordination bonds and a rich tapestry of supramolecular interactions, including H-bonds and halogen bonds, direct the self-assembly of the 17 3-D and three 2-D MOFs. The strength of halogen•••halogen (X•••X) and Ln−O interactions increase as Ln(III) size decreases according to a quadratic function. Preliminary luminescence suggests that Ln-DXTA MOFs are good candidates for the fabrication of luminescence materials since DXTA efficiently sensitizes Tb(III), Eu(III), and Nd(III) emission. This study shows that the manipulation of cations, linkers, and solvents can expand the library of Ln-DXTA MOFs with entries that are similar in network topology but diverse in structural details, including solvent effects and supramolecular interactions.