Three metal-organic frameworks constructed from 3,3′, 5,5′-azobenzene-tetracarboxylic acid: Synthesis, structure and luminescent sensing

Three new metal-organic frameworks (MOFs), namely, {[Zn-2(abtc)(bpa)(H2O)]center dot 5H(2)O}(n) (1), {[Cd-3(abtc) 2]center dot 2H(3)O} n (2) and [Cd-3(H(2)abtc)(3)(bpp)(mu(2)-OH2)(2)(H2O)(3)](n) (3) [bpa = bis(4-pyridyl)amine, bpp = 1,3-bis(4-pyridyl) propane] have been constructed mainly from the ligand of 3,3', 5,5'-azobenzene-tetracarboxylic acid (H(4)abtc) and metal centers of Zn2+ or Cd2+. Single crystal X-ray diffraction analysis reveals that compounds 1 and 2 display 3D frameworks, while compound 3 displays a 2D layered structure consisting of intriguing 1D rhombic chains and bpp ligands. The solid-state luminescent properties of three products are investigated at room temperature. Furthermore, fluorescence measurements indicated that the complex 1 could sensitively sense Fe3+ ions and nitrobenzene molecules.