Transition Metal–organic Coordination Polymers Containing 6‐(1H‐imidazol‐1‐yl)‐2(1H)‐Pyridinone: Synthesis, Structure and Fluorescent Sensing for Enoxacin

Abstract

Three metal–organic coordination polymers, [M(2,6‐bip)2] (M = Zn (1), Ni (2)) and [Cu (tfbdc)(2,6‐bipH)2]•2H2O (3), were obtained with the similar solvothermal reaction systems of bivalent transition metal salt, 6‐(1H‐imidazol‐1‐yl)‐2(1H)‐pyridinone (2,6‐bipH) and 2,3,5,6‐tetrafluoroterephthalic acid (H2tfbdc). The three coordination polymers show different framework features, namely 3D (1), 2D (2) and 1D (3) structures, which are resulted from different single‐metal ion “node” and “linker” coordination modes. The [ZnO2N2] tetrahedron in 1 and [NiO2N4] octahedron in 2 as a node, is formed from Zn sp3 and Ni d2sp3 hybrid orbits, respectively, while the linker, 2,6‐bip, adopts the μ2:η1η1η0 in 1 and μ2:η1η1η1 in 2 coordination modes. PLATON calculation suggests that 1 possesses the micropore structure with a pore volume of 14.2%. In 3, the [CuO2N2] parallelogram as a node is derived from Cu dsp3 hybrid orbital, while the linkers of 2,6‐bipH and tfbdc adopt the μ1:η1η0η0 and μ1:η1η0/μ1:η1η0 coordination modes, respectively. Intriguingly, Zn(d10)‐centre coordination polymer 1 shows strong blue emission, which are derived from the π* → π transition of the 2,6‐bipH ligand. Moreover, 1 exhibits high stability and strong luminescence in both water and ethanol. At this point, the performance of 1 is studied as a chemical sensor for detecting fluoroquinolones drug. The results show that 1 can detect enoxacin in ethanol solution with a low detection limit of 3.61 × 10−5 M. The luminescent sensing mechanisms were investigated from experimental methods and theoretical calculation in detail as well.