Three Zn(ii) metal–organic frameworks assembled from a versatile tecton 5-ethyl-pyridine-2,3-dicarboxylate and dipyridyl-type coligand

Abstract

Solvothermal reactions of 5-ethyl-pyridine-2,3-dicarboxylic acid and dipyridyl-type ligands with Zn(Ac)₂·2H₂O afford three metal–organic frameworks, including {[Zn₂(EPDA)₂(BPP)₂]·(H₂O)}_n(1), [Zn₃(EPDA)₂(HEPDA)₂(BPE)]_n (2) and [Zn₃(EPDA)₂(HEPDA)₂(BPA)]_n (3) (H₂EPDA = 5-ethyl-pyridine-2,3-dicarboxylic acid, BPP = 1,3-di(4-pyridyl)propane, BPE = 1,2-di(4-pyridyl)ethylene and BPA = 1,2-bi(4-pyridyl)ethane). The pronounced structure for 1 represents a rare 2D → 3D interpenetrated framework with new layer motif featuring a 4-connected net signified as Schläfli symbol of (3.6⁴.8)(3².6.7².8). Complexes 2 and 3 possess intimately related structures featuring infinite Zn carboxylate layers of [Zn₃(EPDA)₂(HEPDA)₂]_n pillared by a BPE (or BPA) molecule to produce the three-dimensional frameworks with pcu topology based on the Zn trimers as the 6-connected nodes. It is shown that the flexible degree of dipyridyl-type molecules plays a key role for the assembly of diversified coordination networks. Furthermore, thermal degeneration and fluorescence properties of all three complexes are also investigated.