Highly selective and sensitive detection of metal ions and nitroaromatic compounds by an anionic europium() coordination polymer

A luminescent Eu( iii )-based coordination polymer, {[Eu(H 2 O) 5 (BTEC)][H(C 5 H 6 N 2 )]·3H 2 O} ( 1 ) has been synthesized under hydrothermal conditions using 1,2,4,5-benzenetetracarboxylic acid (H 4 BTEC) as a linker. Compound 1 possesses an anionic zig-zag chain constructed from the BTEC ligands and [EuO 4 (H 2 O) 5 ] nodes. The protonated 4-aminopyridine groups as guests are located between chains. 1 exhibits the characteristic sharp emission bands of Eu 3+ at 578, 593, 615, 652 and 693 nm upon excitation at 290 nm. The strong emission of 1 could be quenched effectively by trace amounts of Fe 3+ ions even in the presence of other metal ions including Al 3+ , Ca 2+ , Cd 2+ , Co 2+ , Cr 3+ , Cu 2+ , Fe 2+ , K + , Mg 2+ , Mn 2+ , Pd 2+ and Zn 2+ . Similarly, 1 also exhibits superior selectivity and sensitivity towards 4-nitrophenol (4-NP) compared with other competing interfering analytes, such as 2,4,6-trinitrophenol, 2,6-dinitrotolune, 4-nitrotoluene, nitrobenzene, 1,3-dinitrobenzene, o -xylene, nitromethane, nitropropane, phenol, 4-bromophenol and bromobenzene, through a fluorescence quenching mechanism. The possible fluorescence quenching mechanisms are discussed. Moreover, 1 could be used as a visual fluorescent test paper for selectively detecting trace amounts of Fe 3+ and 4-NP. A luminescent Eu( iii )-based coordination polymer has been synthesized, which can serve as a visual selective sensor for the detection of 4-nitrophenol and Fe 3+ ions via a fluorescence quenching mechanism.