Fluorescence turn-on detection of Fe3+ in pure water based on a cationic poly(perylene diimide) derivative

摘要

Polycondensation of perylene diimide (PDI) diamines with a 2,2 ':6 ',2 ''-terpyridine (tpy)-containing dibromide gives a new fluorescent polymeric chemosensor (L) with good water solubility. L exhibits good selectivity for Fe3+ ions over a wide range of tested metal ions Ag+, K+, Na+, Fe2+, Cu2+, Al3+, Cr3+, Mn2+, Mg2+, Ni2+, Ca2+, Hg2+, Pd2+, Ba2+, Cd2+, Co2+ and Zn2+ in aqueous solution. The binding of Fe3+ to chemosensor L leads to significant emission bands at 548 nm and 591 nm, respectively, because the complexation of Fe3+ with the tpy moiety of L blocks the photoinduced electron transfer (PET) from tpy units to PDI units. A 1 : 2 stoichiometry was found for the complex formed by L and Fe3+ by Job's plot. The association constant (K-a) of Fe3+ binding in chemosensor L is 1.32 x 10(8) M-2. L can be used to detect Fe3+ over a wide pH range of 5.0-9.0. Moreover, by taking advantage of its instant fluorescence turn-on specific to Fe3+, L is used as a fluorescent probe to monitor the Fe3+/Fe2+ transition in the presence of reducing agents such as Na2S2O3 or ascorbic acid (Vc) in water. L can also work well in biological samples, which gives access to the detection of Fe3+ in an organism.