Syntheses, characterizations and properties of five new metal–organic complexes based on flexible ligand 4,4′-(phenylazanediyl)dibenzoic acid

Abstract

Five new metal–organic frameworks have been synthesized under hydrothermal conditions, in CH₃CN–H₂O, DMF–CH₃CH₂OH–H₂O and DMA–H₂O, namely, [ZnL(bimx)_0.5]_n (1), {[CoL(4,4′-bipy)]·DMF}_n (2), {[CdL(4,4′-bipy)]·DMF}_n (3), {[ZnL(bibp)]·DMA·(H₂O)₂}_n (4), {[CoL(bpyb)_0.5]·(H₂O)₂}_n (5) (bimx = 1,4-bis(imidazol-1-ylmethyl)benzene, 4,4′-biby = 4,4-pyridine, bibp = 4,4′-bis(imidazol-1-yl)biphenyl, bpyb = 1,4-bis(4-pyridyl)benzene, H₂L = 4,4′-(phenylazanediyl)dibenzoic acid. These complexes were characterized by elemental analysis, IR spectroscopy, TG and X-ray single-crystal diffraction. In compounds 1, 2 and 3, the bimx, 4,4′-bipy and L²⁻ anions act as bidentate ligands assembling with metal cations to form two-dimensional (2D) sheets. The sheets are stacked in ABAB fashion and accumulate into a 3D framework. Compound 4 possesses a 3D→3D 4-fold interpenetrating architecture with {6⁵·8} topological net, which is similar to the cds topology. Compound 5 also displays a 3D structure with {4⁴·6¹⁰·8} topology. The photochemical properties were investigated in the solid state at room temperature. The luminescent properties of compounds 1, 3 and 4 are discussed in detail. The UV-vis absorption spectra of compounds 2 and 5 are tested and discussed. In addition, the magnetic properties of compound 5 also are tested and simply analyzed.