Two donor-acceptor (D-A) type Zn(II) complexes as fluorescent probes for highly selective detection of iodide

Two D-A type Zn(II) coordination complexes ([Zn-2(L-1)(2)(MeCN)(MeOH)]center dot(MeCN) (1) and [ZnL2(H2O)] (2)) were synthesized from diaminomaleonitrile-based (DMN) Schiff-base ligands (L-1 = 2-amino-3-[(2-hydroxynaphthalen-1-ylmethylene)-amino]-but-2-enedinitrile, L-2 = 2-[(4-chloro-2-hydroxybenzylidene)-amino]-3-[(2-hydroxynaphthalen-1-ylmethylene)-amino]-but-2-enedinitrile). Based on the weak blue fluorescence in THF solution and the bright yellow fluorescence in the solid state, the ligand L-1 shows obvious aggregation induced emission (AIE) in a THF-H2O solvent system. The fluorescence emission of complexes 1 and 2 exhibits a significant red-shift relative to that of the ligand in THF solution. Interestingly, because of aggregation caused by the interaction between L-1 and iodide (I-), complexes 1 and 2 exhibit excellent selectivity for fluorescence detecting iodide, and the quenching efficiency of 2 with iodide is higher than that of 1.