A series of metal–organic frameworks based on 9,10-bis(imidazol-1-ylmethyl)anthracene and structurally related aromatic dicarboxylates: Syntheses, structures, and photoluminescence

A series of new metal–organic frameworks (MOFs) based on 9,10-bis(imidazol-1-ylmethyl)anthracene and four structurally related aromatic dicarboxylates, namely, [Cd(L)(o-bdc)]·1.25H2O (1), [Cd(L)(pydc)] (2), [Zn(L)(pydc)] (3), [Cd3(L)2(m-bdc)3] (4) and [Cd(L)(p-bdc)]·2H2O (5) (L = 9,10-bis(imidazol-1-ylmethyl)anthracene, o-H2bdc = 1,2-benzenedicarboxylic acid, H2pydc = 2,3-pyridinedicarboxylic acid, m-H2bdc = 1,3-benzenedicarboxylic acid, p-H2bdc = 1,4-benzenedicarboxylic acid) have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses, and further characterized by infrared spectra (IR), elemental analyses and powder X-ray diffraction (PXRD). Compound 1 displays a two-dimensional (2D) layer structure, which is stabilized by intramolecular hydrogen-bonding interactions. Compounds 2 and 3 are isostructural and show 2D layer structures, which are further extended by intermolecular C–H···O hydrogen-bonding interactions to form 3D supramolecular frameworks. Compound 4 has a 2D layer structure with trinuclear units [Cd3(u3-O)2]6+. Compound 5 is a 3D three-fold interpenetrating framework with a Schläfli symbol (66·8). The structural differences of these compounds indicate that the anions play important roles in the resulting structures of the MOFs. The luminescent properties were also investigated for compounds 1–5.

Graphical abstractA series of metal–organic frameworks based on 9,10-bis(imidazol-1-ylmethyl)anthracene have been successfully synthesized by varying the metal centers and the organic anions, where their photoluminescent properties were also investigated.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The choice of carboxylate anions is critical in determining the ultimate structures. ► The positions of the carboxylate groups led to the differences of 1, 4 and 5. ►1 and 2 display the effects of heteroatom in the benzene ring on the structures.