A series of pillar-layer metal-organic frameworks based on 5-aminoisophthalic acid and 4,4′-bipyridine

Four new compounds, [Cd(5-aip)(bpy)]center dot 1.5DMA (1), [Cu(5-aip)(bpy)]center dot 1.3DMA (2), [Co(5-aip)(bpy)]center dot 1.6DMA (3), and [Cd(5-aip)(bpy)(0.5)(H2O)]center dot 1.3DMA (4), based on 5-aminoisophthalic acid and 4,4'-bipyridine, have been synthesized by the solvothermal method and structurally determined using single crystal X-ray diffraction. Compounds 1-3 are structurally similar and show non-interpenetrating three-dimensional (3D) pillar-layer frameworks, while compound 4 displays a two-dimensional (2D) (3,4)-connected parallel non-interpenetrating architecture. In all these compounds, 1D rectangular channels are observed and the ligand 5-aminoisophthalic acid exhibits three kinds of coordination modes. Furthermore, 1 displays a single-crystal-to-single-crystal transformation when immersed in a methanol solution. More significantly, 1 can absorb and deliver I-2 molecules by means of its channels, and could induce a reversible luminescent transformation from quenching to the initial state. The luminescent properties of 1 and 4 have also been studied.