A series of coordination polymers based on terphenyl tetracarboxylates and bis-pyridyl ligands with water vapor sorption properties

Abstract

Six new coordination polymers, namely, {[Mn₂(L1)(bpfp)(H₂O)₂]·6H₂O·(CH₃OH)}_n (1), {[Mn₄(μ₃-O)₂(L1)₂(bpe)₂(H₂O)₂]·2H₂O}_n (2), [Ni(HL1)(Hbpmp)(H₂O)₂]_n (3), [Co₂(μ₂-OH)(HL1)(bpmp)(H₂O)₄]_n (4), {[Co₂(L2)(bpfp)(H₂O)₂]·4H₂O}_n (5), {[Co₂(L2)₂(bpe)₂(H₂O)₂·2H₂O]·(NH₄)₄}_n (6) (H₄L1 = [1,1′:4′,1′′-terphenyl]-2,2′′,5,5′′-tetracarboxylic acid, H₄L2 = [1,1′:4′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid, bpfp = bis(4-pyridylformyl)piperazine, bpe = 1,2-bis(pyridin-4-yl)ethane and bpmp = N,N′-bis(4-pyridyl)piperazine) were synthesized under hydrothermal conditions by terphenyl tetracarboxylates, bis-pyridyl ligands and transition metal salts. These six complexes were characterized by elemental analysis, infrared (IR) spectroscopy, thermogravimetric analysis (TGA), single-crystal X-ray diffraction, powder X-ray diffraction (PXRD) and fluorescence spectroscopy. Complexes 1 and 5 possess three-dimensional (3D) (4,6)-connected networks with {4³·6³}₂{4⁶·6⁶·8³} and {4⁴·6¹⁰·8}{4⁴·6²} topologies, respectively. Complexes 2–4 and 6 feature two-dimensional (2D) networks, which are expanded into 3D supramolecular frameworks via hydrogen bonding interactions. Desorption of lattice water molecules in complexes 1 and 2 was analyzed, and the values of water vapor uptake are 15.17 mL g⁻¹ and 27.24 mL g⁻¹, respectively.