(R,R)-salen/salan-based polymer fluorescence sensors for Zn2+ detection

(R,R)-salen-based polymer fluorescence sensor P-1 could be synthesized by the polymerization of 5,5′-(isoquinoline-5,8-diylbis(ethyne-2,1-diyl))-bis(3-tert-butyl-2-hydroxybenzaldehyde) (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via nucleophilic addition–elimination reaction, and (R,R)-salan-based polymer sensor P-2 could be obtained by the reduction reaction of P-1 with NaBH4. The fluorescence response behaviors of two chiral polymers P-1 and P-2 on Zn2+ were investigated by fluorescence spectra. The fluorescence intensities of P-1 and P-2 can exhibit gradual enhancement upon addition of Zn2+. Compared with other cations, such as Na+, K+, Mg2+, Ca2+, Fe3+, Co2+, Ni2+, Cu2+, Ag+, Cd2+, Cr3+ and Pb2+, Zn2+ can lead to the pronounced fluorescence enhancement as high as 22.8-fold for P-1 and 3.75-fold for P-2, respectively. The results show that P-1 and P-2 incorporating (R,R)-salen/salan moieties as receptors in the polymer main chain backbone can exhibit high sensitivity and selectivity for Zn2+ detection.