Ancillary Ligands Dependent Structural Diversity of A Series of Metal–Organic Frameworks Based on 3,5-Bis(3-carboxyphenyl)pyridine

A series of novel multidimensional transition metal–organic frameworks (MOFs), [Cu(Hbcpb)2] n (1), [Co(bcpb)] n (2), [Co(Hbcpb)2(1,4-bib)]n (3), {[M(bcpb)(1,4-bimb)]·xH2O}n (M = Co (4), Cu (5), Ni (6), x = 1 for 5, 2 for 4 and 6), [Co(bcpb)(4,4′-bibp)] n (7), {[Co(bcpb)(4,4′-bibp)]·2H2O} n (8), and [Ni2(bcpb)2(4,4′-bimbp)2] n (9), were synthesized under hydrothermal conditions in the presence of N-donor ancillary ligands [H2bcpb = 3,5-bis(3-carboxyphenyl)pyridine, 1,4-bib = 1,4-bis(1H-imidazol-4-yl)benzene, 1,4-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl, 4,4′-bimbp = 4,4′-bis(imidazol-1-ylmethyl)biphenyl]. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. By adjusting the reaction pH, the H2bcpb ligand is partially deprotonated to give the Hbcpb– form in 1 and 3, and completely deprotonated to afford the bcpb2– form in 2 and 4–9. Complex 1 exhibits a two-dimensional (2D) (3,6)-connected kgd topology with the Schläfli symbol of (43)2(46·66·83). The three-dimensional (3D) framework of 2 is defined as a (4,4)-connected pts topology with the Schläfli symbol of (42·84). Complex 3 displays a (4,6)-connected pcu topology with the Schläfli symbol of (412·63) built from 44 2D nets with the help of 1,4-bib. Complexes 4–6 are isomorphism and show a 3D (3,5)-connected mbm framework with the Point Schläfli symbol of (4·62)(4·66·83). The supramolecular isomers of 7 and 8, resulted from the different pH in the reaction, exhibit (3,5)-connected (42·67·8)(42·6) 3,5-L2 and (4,6)-connected (44·610·8)(44·62) fsc topology, respectively. Complex 9 can be regard as an unprecedented (3,5)-connected 3D 3,5-T1 frameworks with the point Schläfli symbol of (42·65·83)(42·6). The results revealed that the crystal architectures and the coordination modes of H2bcpb are attributed to the factors, including metal cations, pH, and the N-donor ancillary ligands.