An efficient vanillinyl Schiff base as a turn on fluorescent probe for zinc(ii) and cell imaging

Abstract

6,6′-((1Z,1′Z)-(((Ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(azanylylidene))bis(methanyl ylidene))bis(3-methoxyphenol), a vanillinyl Schiff base, shows unprecedented fluorescent zinc sensing properties and has been examined for zinc bioimaging. Zinc induced turn-on fluorescence enhancement is observed at 472 nm and steady state photophysical studies establish the metal promoted deprotonation and chelation enhancement of emission. Formation of the 1 : 1 metal-to-ligand complex has been ascertained by ¹H NMR, mass spectral analysis and Job's plot. Limit of detection (LOD) is the lowest, 0.018 μM in the family of fluorogenic Zn²⁺-sensors. Apart from this, theoretical interpretation of the experimental outcome has also been obtained by applying density functional theory (DFT) to the ligand and the complex. The practical applicability of the ligand has been examined in living cells (African Monkey Vero Cells). MTT assay proves the no toxicity of probe upto 300 μg ml⁻¹.