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

Abstract

A luminescent Eu(III)-based coordination polymer, {[Eu(H₂O)₅(BTEC)][H(C₅H₆N₂)]·3H₂O} (1) has been synthesized under hydrothermal conditions using 1,2,4,5-benzenetetracarboxylic acid (H₄BTEC) as a linker. Compound 1 possesses an anionic zig-zag chain constructed from the BTEC ligands and [EuO₄(H₂O)₅] nodes. The protonated 4-aminopyridine groups as guests are located between chains. 1 exhibits the characteristic sharp emission bands of Eu³⁺ 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 Fe³⁺ ions even in the presence of other metal ions including Al³⁺, Ca²⁺, Cd²⁺, Co²⁺, Cr³⁺, Cu²⁺, Fe²⁺, K⁺, Mg²⁺, Mn²⁺, Pd²⁺ and Zn²⁺. 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 Fe³⁺ and 4-NP.