Multi-responsive fluorescent sensor based on Cu(II) coordination polymer for selective detection of acetylacetone and Cr(VI) ions

A novel Cu(II) coordination polymer [Cu(HL)(4,4'-bpy)](n) (4,4'-bpy = 4,4'-bipyridine) 1 based on a semi-rigid tricarboxylate, 5-(3,4-dicarboxylphenoxy) nicotinic acid (H3L) has been hydrothermally synthesized. Single-crystal X-ray diffraction analysis indicates that, in compound 1, H3L ligands first extend the metal ions into a 2-D layer. Then the 4,4'-bpy molecules functioned as bidentate bridge, strutting the 2-D layers into a 3-D open network with a (6(3)) (6(9).8) topology. Notably, 1-D channels of ca. 6.5 x 10.5 angstrom(2) are observed in 1, but due to 2-fold interpenetration phenomenon, these channels become small or disappear. Fluorescent spectra indicate 1 can act as a muti-chemosensor for detection of acetylacetone (Hacac), Cr2O72- and CrO42- in aqueous solution with high selectivity and sensitivity. The mechanism of luminescent sensing Hacac and Cr(VI) were also investigated in detail.