An AIRE active Schiff base bearing coumarin and pyrrole unit: Cu2+ detection in either solution or aggregation states

A new fluorescent molecular probe 1, derived from 3-(1-aminoiminethyl)-4-hydroxycoumarine and 2-formyl-3,5-dimethyl-1H-pyrrole by a simple Schiff base condensation, was designed, synthesised and accurately characterized. The aggregation induced ratiometric emission (AIRE) active probe 1 showed selective interaction with Cu2+ in both 1:1 and 9:1 H2O/DMSO solutions (v:v, buffered by 10 mM HEPES at pH = 7.4). However, the sensing mechanism was found to be different in each media. In H2O/DMSO 1:1 solution, 1 exhibited a coumarin emission at 525 nm and the addition of Cu2+ results in a coordination complex under strong Photoinduced Electron Transfer (PET) process. Conversely, TEM studies revealed that probe 1 organizes itself as mono disperse aggregates in H2O/DMSO 9:1 solution with the emission at 585 nm, and further disassembly of aggregates was induced by the addition of Cu2+, accomplishing with the fluorescence quenching. The application of the fluorescent sensor in monitoring intracellular Cu2+ in HeLa cells was also demonstrated. (c) 2018 Elsevier B.V. All rights reserved.