Zn(II) metal-organic frameworks (MOFs) assembled from semirigid multicarboxylate ligands: Synthesis, crystal structures, and luminescent properties

Two new coordination polymers [Zn2L(2,2′-bpy)]n∙(H2O)2n (1) and [Zn2L(phen)]n∙(H2O)2n (2) have been assembled from a semirigid multicarboxylate ligand 3,3′-(1,3-phenylenebis(oxy))diphthalic acid (H4L) with the help of 2,2′-bipyridine (2,2′-bpy) or 1,10-phenanthroline (phen) as secondary ligand. Single crystal X-ray diffraction analysis reveals that complex 1 crystallizes in the space group C2/c and displays a one-dimensional (1D) chain structure constructed from 2,2′-bpy and L ligand, which further forms a two-dimensional (2D) plane via intermolecular π–π interactions. Compound 2 belongs to the space group P1¯ and features a 1D Δ- and Λ-typed chiral chain configuration despite the racemic nature for the whole complex. The neighboring chains with the same chirality are further stacked into a 2D ΔΔΔ- or ΛΛΛ-typed supramolecular structure via intermolecular π–π interactions because of the chiral recognition mechanism. Photophysical properties over complexes 1 and 2 have been comparatively investigated, revealing the effect of secondary ligand on the luminescent properties of these two complexes.

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