Construction of a series of metal–organic frameworks with a neutral tetradentate ligand and rigid carboxylate co-ligands

Abstract

The solvothermal reaction of a neutral tetradentate ligand, different bivalent metal salts and two rigid carboxylate co-ligands gave six metal–organic frameworks (MOFs): [Zn(L)(Hbdc)(bdc)_0.5]·1.5H₂O (1), [Zn₂(L)(bdc)₂(H₂O)]·2H₂O (2), [Cd(L)(bdc)(H₂O)]·2H₂O (3), [Ni(L)(bdc)(H₂O)]·H₂O (4), [Co₃(L)(btc)₂(H₂O)₄] (5), [Zn₃(L)(btc)₂(H₂O)₄] (6) (L = 1,1′-oxybis[3,5-dipyridine]-benzene, H₂bdc = 1,4-benzenedicarboxylate, H₃btc = 1,3,5-benzenetricarboxylate). Compounds 1 and 2 have been co-crystallized in a one-pot reaction. In compound 1, L and H₂bdc ligands link Zn centers to generate a two-dimensional (2D) sheet structure which is further connected by intermolecular hydrogen bonds to form a 3-fold interpenetrating 3D fsc-3,4-C2/c array. Single crystal X-ray diffraction analysis reveals that compound 2 features a 3D self-interpenetrated network with {4·6·8³·10}{4·6³·8²}{6⁴·8²} topology. For compounds 3 and 4, the binuclear metal secondary building unit (SBU) assembles with mixed ligands, L and H₂bdc, to construct a 3D α-Po structure. Compounds 5 and 6 are isostructural and show 3-fold interpenetrated pte/Cmmm->P2/c structures.