A potential fluorescent sensor for Zn2+ based on a selective bis-9-anthryldiamine ligand operating in buffer

We herein report on the synthesis and characterization of two similar bis-9-anthryldiamine ligands, N,N′-bis(anthrylmethyl)-ethylene diamine (BAEDA) and N,N′-bis(anthrylmethyl)-propylene diamine (BAPDA) and the crystal structure of one ZnII coordination complex of BAPDA. In pure organic solvents, BAPDA displayed strong fluorescence enhancement titrated by Zn2+, but the emission of the complex could be remarkably quenched by a trace amount of water, which hence showed less applicable potential for detection of Zn2+. While BAEDA was found to be an excellent fluorescent responsor for Zn2+, which could operate in a HEPES buffer (pH 7.5, 100 mM, H2O/THF = 1/1). The fluorescent intensity achieved nearly a 6.5-fold increase after the addition of 10 equivalents of Zn2+. Moreover, BAEDA had remarkably higher selectivity to Zn2+ than that to other heavy metal ions, such as Ag+, Cu2+, Pb2+, Mn2+, Co2+, Hg2+, Ni2+, Fe2+, etc., indicating that BAEDA may be a potential fluorescent sensor for Zn2+.