Four Novel Cobalt(II) Coordination Polymers Based on Anthracene-Derived Dicarboxylic Acid as Multi-functional Fluorescent Sensors toward Different Inorganic Ions

Abstract

A series of Co(II)–H 2 L coordination polymers were prepared with different auxiliary ligands, namely {[Co(L)(bibp)]} n 1, {[Co(L) (bpy)(H 2 O)] 2 ·2H 2 O} n 2, {[Co(L)(bipd)]} n 3, and {[Co(L)(bbibp)]·H 2 O} n 4 (H 2 L = 5-{(anthracene-9-ylmethyl)amino}isophthalic acid, bibp = 4,4′-bis(imidazolyl)biphenyl, bpy = 2,2′-bipyridine, bipd = 3,5-bis(1-imidazoly)pyridine, and bbibp = 4,4′-bis(benzoimidazo-1-yl)biphenyl), by a similar solvothermal method. X-ray diffraction analyses revealed that 1, 3, and 4 exhibit a two-dimensional (2D) structure, which further builds the three-dimensional (3D) supramolecular architecture via the weakly interacting hydrogen bonds of C–H···O, while 2 displayed a one-dimensional (1D) double-chain architecture extended from two 1D zigzag chains by intermolecular hydrogen bonding interactions. The sensing experiments revealed that 1 and 2 can serve as either individual- and/or multi-responsive sensors to selectively detect Cr 3+, Al 3+, and Pb 2+ ions through the fluorescence turn-on effect, while 3 – 4 exhibited fluorescence turn-off sensing behavior for Fe 3+ ions. Moreover, 1 – 4 can effectively detect and recognize Cr 2 O 7 2– and CrO 4 2– due to their high selectivity and sensitivity for fluorescence quenching in aqueous solutions, and the sensing mechanism for various ions has been discussed.