Two- and three-dimensional lanthanide metal-organic frameworks with hydroxyl-functionalized nicotinic acid and oxalate ligands

A series of LMOFs, consisting of three groups of isostructural compounds, [Ln(3-H-5-phenoxonicotinato)(ox)(H2O)2]n 1 (Ln = La(1a), Pr(1b), Nd(1c), 5-Hydroxynicotinic acid = C6H5NO3, ox = C2O42 −), {[Ln(3-H-5-hydroxynicotinato)(ox)1.5(H2O)]⋅H2O}n 2 (Ln = Sm(2a), Gd(2b), Tb(2c), and {[Ln(3-H-5-phenoxonicotinato)(ox)(H2O)]⋅H2O}n 3 (Ln = Dy(3a), Er(3b), have been hydrothermally synthesized and structurally determined by X-ray diffraction analyses. Compounds in group 1 are constructed by mixed μ3-3-H-5-phenoxonicotinato and oxalate bridging ligands and Ln3 + ions, exhibiting a 3D covalent network with empty 1D microchannels, featuring a 3,5-connected topology symbol of {42⋅ 65⋅ 83}⋅{42⋅ 6}. Compounds in group 2 present a brick-well-liked 2D network generated by both metal ions and oxalate groups at a side-by-side way. Compounds in group 3 are isotopological to those in group 1, accompanying 1D microchannels being occupied by coordinated water molecules. Antiferromagnetic interactions between praseodymium metal centers are observed from the magnetic susceptibility of compound 1b. In addition, luminescence measurements indicate that the terbium complex 2c is a strong green luminescence emitter.