AIE active hydroxycoumarin-anthranilic acid coupled enamine: Sequential detection of Cu2+/S2-ions and live cell imaging application

In this contribution, we designed and developed 7-diethylamino- 4-hydroxycoumarin coupled anthranilic acid- based enamine ( DHCBA ) and its Cu2+ complex ( DHCBA-Cu) via simple synthetic strategy. DHCBA shows solvatochromic effect, aggregation induced emission feature at 80 % methanol-water mixture and colorimetric as well as fluorescence turn-off sensing features towards Cu2+ ions. The DHCBA-Cu2 & thorn; ensemble has been utilized as a turn-on fluorescence sensor for the detection of S 2- through a decomplexation approach. The formation of a 1:1 DHCBA-Cu2 & thorn; ensemble was further supported by 1 H NMR studies, HRMS analysis and Density Functional Theory (DFT) calculation. The detection limit for Cu2+ was found to be 6.5 nM and then the binding affinity and binding stoichiometry of the probe towards Cu2+ ion was calculated using the online BindFit v0.5 supramolecular software. Moreover, the 1:1 stoichiometric ratio between DHCBA and Cu2+ ions were confirmed via single crystal X-ray analysis. The structural analysis of DHCBA-Cu2 & thorn; indicates that it forms an interesting onedimensional coordination polymeric chain-like structure, further transformed into a two-dimensional polymeric network through hydrogen bonding interactions. The reversible on-off-on emission character of the probe, DHCBA was successfully applied for the construction of the IMPLICATION logic gate as well as on-site detection applications using paper strip and cotton-swab tests. Furthermore, the sensing feature of the enamine against Cu2+/S2- ions were validated by intracellular imaging applications.