A New «off-on» Fluorescence Zinc Ion Sensors Based on Iodo- and Bromosubstituted Dipyrromethenes

Monoiodo- and dibromsubstituted dipyrromethenes HL1 – HL3 were described as a highly sensitive and selective «Off-On» fluorescent chemosensor for Zn2+ based on the chelation-enhanced fluorescence (CHEF) effect. Сoordination reactions of HL1 – HL3 with Zn2+ cations are accompanied by a significant (124 to 215-fold) increase in fluorescence intensity against the background of other metal ions in the binary propanol-1/cyclohexane mixture (1:30). The fluorometric detection limit of Zn2+ ions using HL1 – HL3 sensors is from 3.0∙10−8 to 3.3·10−9 mol/L. The presence of Na+, K+, Ca2+, Mg2+, Mn2+, Ni2+, Co2+, Pb2+ cations does not interfere with the detection of Zn2+. Complexation reactions are accompanied by a visual change in the color of the solution from yellow-orange to pink-raspberry so that the HL1 – HL3 ligands can also be used as a «naked-eye» indicators of the presence of Zn2+ ions.