Crystal structures from 1D to 3D: triggered by the different coordination morphologies of ligands in different reaction systems†
Abstract
In this report, seven new luminescent metal–organic frameworks (LMOFs), [Zn(L)0.5(H2O)2]·H2O (1), [Zn(L)0.5(DMF)] (2), [Zn3(L)(μ3-OH)2(H2O)4] (3), [Zn2(L)(DMA)(H2O)]·5(H2O) (4), [Cd(L)]·2(H3O)·(H2O) (5), [Cd2(L)(H2O)3] (6), and [Pb(L)0.5(H2O)] (7) (H4L = [1,1′:4′,1′′-terphenyl]-2′,3,3′′,5′-tetracarboxylic acid; DMF = N,N-dimethylformamide; DMA = N,N-dimethylacetamide) have been solvothermally synthesized by using Zn(II), Cd(II), Pb(II) ions and H4L in different solvent systems, all of which have been routinely characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analyses show the different dimensionalities (1D, 2D or 3D) of complexes 1–7. Comparative structural studies of 1–7 reveal that the L4− ligands adopt different coordination morphologies: 1 (η1μ1χ1), 2 (η2μ2χ2), 3 (η2μ2χ2), 4 (η2μ2χ2; η1μ1χ1), 5 (η2μ1χ2), 6 (η2μ2χ2; η2μ2χ3), and 7 (η2μ2χ2; η2μ3χ4) with Zn(II) (74 pm), Cd(II) (97 pm) and Pb(II) (119 pm) in different solvent systems, which produce the complexes with different frameworks. Complex 1 displays a 1D dimeric chain. Complexes 2 and 5 present a 2D layer structure with a uninodal 4-connected sql net with a symbol of (44·62). Complexes 3, 6 and 7 have a 3D dense packing structure based on infinite 1D rod-like secondary building units (SBUs). Complex 3 is designated as a binodal (4, 6)-connected fry topological net with the point symbol (510·63·78)(54·62). The whole network of 6 can be simplified as a binodal (4, 8)-connected flu topological net with a point symbol of (412·612·84)(46)2. Complex 7 can be seen as a new binodal (5, 10)-connected topological net with the point symbol (410)2(428·616·8). Complex 4 shows a 3D framework based on a binuclear [Zn2(CO)3O3] SBU, which can be viewed as a uninodal 4-connected sra topological net with the point symbol (42·63·8). Further, the solid-state luminescence properties of the complexes were measured and studied intensively at room temperature.