Acentric and chiral four-connected metal–organic frameworks based on the racemic binaphthol-like chiral ligand of 4-(1-H(or methyl)-imidaozol-1-yl)benzoic acid

Abstract

By modulating the synthetic strategy based on changing substituents on the ligand and solvent used in the synthesis, a series of metal organic frameworks (MOFs) of two chiral binaphthol-like ligands of 4-(1H-imidaozol-1-yl)benzoic acid (HIBA) and 4-(1H-2-methylimidazol-1-yl)benzoic acid (HMIBA) with various interpenetrating topologies have been synthesized under solvothermal conditions: Zn(IBA)₂ (1), Co(IBA)₂ (2), Cd(IBA)₂·H₂O·1.7DMF (3), Cd(MIBA)₂·H₂O·1.3DMF (4), Co(MIBA)₂·H₂O·1.3DMF (5) and Cd(MIBA)₂·0.5H₂O·1.2DMA (6) (DMF = N,N-dimethylformamide and DMA = N,N′-dimethylacetamide). X-ray diffraction study reveals that compounds 1 and 2 crystallize in tetragonal crystal system with chiral space groupsP4₁22 and P4₃22, respectively, indicating that they are a pair of structural enantiomers, having a twofold interpenetrating (4,4)-net. Compound 3 crystallizes in orthorhombic crystal system and non-centrosymmetric space group Pca2₁, which can be defined as an abnormal fourfold [2 + 2] interpenetrating diamond net. The isostructural compounds 4 and 5 crystallize in tetragonal crystal system and space group P42₁2, representing a chiral structure and a normal mode of fourfold interpenetrating diamondoid net. Compound 6 crystallizes in non-centrosymmetric space group Aba2 and exhibits a normal mode of fourfold diamondoid interpenetrating net.