Macrocyclic "tet a" derived colorimetric sensor for the detection of mercury cations and hydrogen sulphate anions and its bio-imaging in living cells.

A mono-N-substituted probe L containing a bromosalicylaldehyde pendant arm attached to a tetraazamacrocyclic "tet a" moiety was synthesized via straight forward reaction. The probe L crystallizes in a monoclinic P2/n space group. The probe L displayed quick sensitivity and selectivity towards Hg ions due to its hopeful Chelation Enhancement Quenching (CHEQ) feature. Interestingly, the probe L exhibits turn-off fluorescence response to Hg ion and turn-on fluorescence signals to HSO ions. When the probe L was complexed with HSO in 1:1 mode (L + HSO formation), improved turn-on fluorescence emission was detected due to the chelation enhanced fluorescence effect through sensor complex. The macrocyclic "tet a" probe L exhibited a binding constant value of 3.89 × 10 M and 5.58 × 10 M for Hg and HSO, respectively. Probe L exhibited good selectivity to Hg rather than other common metal ions and HSO over other common anions. The limit of detection (LOD) of Hg and HSO were found to be 1 nM and 7 μM, respectively. The time-resolved fluorescence emission single-photon counting study was used to determine the average lifetime value for the probe L and L + HSO ions as 0.47 and 1.02 ns, respectively. The practical application of the probe in visualizing intracellular Hg and HSO ions distribution in live Artemia salina was demonstrated. Furthermore, the probe L with Hgcations was found to be cytotoxic against breast cancer cells in nature and can be delivered as an anticancer agent. Besides the probe L with HSO exhibit strong fluorescence emission with low cytotoxicity, and it can be recommended for live-cell imaging.