Fluorescent water-stable Zn (II) coordination polymers for selective aqueous detection of nitrophenols

Two cyclen-based multidentate N,O ligands, 1,4,7,10-tetrazazcyclododecane-N,N′,N″,N″′-tetra- p -methylbenzoic acid (H 4 L 1 ) and 1,4,7,10-tetrazazcyclododecane-N,N′,N″,N″′-tetra- p -cinnamic acid (H 4 L 2 ), were reacted with Zn (II) salts leading to a four-fold interpenetrated 3D binodal PtS-type network {[Zn 2 (HL 1 )Cl]·5H 2 O} n ( Zn-1) along with a 1D ribbon-like polymeric chain {[Zn 3 (HL 2 )Cl 3 (H 2 O) 2 ]·2CH 3 COCH 3 ·3H 2 O} n ( Zn-2 ). Both two compounds exhibited excellent water stability in a wide pH range from 2 to 12 and emitted either UV or visible blue-purple light. They can behave as recyclable fluorescent probes for highly selective sensing of nitrophenols with low detection limits. Additionally, the blue-purple emission of Zn-2 can be efficiently quenched by PA with a concentration as low as 20 μM; thus, the naked-eye detection of PA can be fulfilled under a 365 nm UV lamp. Based on the DFT calculation and spectral analysis evidences, it can be proposed that the selective detection of nitrophenols by two Zn (II) compounds is owing to a synergistic effect of different quenching mechanisms along with the interactions between probes and analytes.