Six isostructural lanthanide-containing MOFs built on a semi-rigid tripodal organic ligand

Abstract

By using a semi-rigid tripodal ligand 1,1′,1′′-(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)tripyridinium-4-olate) (L), six isomorphous lanthanum metal-organic frameworks (MOFs), namely, [Pr(L)2(Cl)2]·(Cl)(DMF)0.5·(H2O)·(1), [Nd(L)2(Cl)2]·(Cl)(2), [Tb(L)2(Cl)2]·(Cl)·(DMF)·(H2O)(3), [Eu(L)2(Cl)2]·(Cl)(DMF)·(H2O)(4), [La(L)2(Cl)2]·(Cl)(5), [Sm(L)2(Cl)2]·(Cl) (DMF)·(H2O) (6), were obtained and characterized by single crystal X-ray diffraction, IR and elemental analysis. Six compounds are isostructural with Ln3+ (Ln=Pr, Nd, Tb, Eu, La, Sm) and in which the Ln3+ is considered as a 6-connecting node and the L ligand is a 3-connecting node to afford a (3,6)-connected 2D layer with kgd topology, which further stacks into 3D supramolecular networks through C-H…O weak interactions. Luminescent properties of these lanthanide MOFs have also been assessed at ambient temperature, in which the Pr3+-1 and the La3+-5 are slightly blue-shifted with respect to the ligand. Series of sharp peaks characteristic of the Eu3+-4, the Tb3+-3 and Sm3+−6 metal-centered luminescence appear. The Nd3+-2 has no emission.