Turn on macrocyclic chemosensor for Al³⁺ ion with facile synthesis and application in live cell imaging

An effort of a new Schiff base macrocyclic chemosensor, 1⁴‑methyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecaphane‑2,5,8,11,14,17‑hexaene (me1) and 1⁴,7⁴‑dimethyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecadecaphane‑2,5,8,11,14,17‑hexaene (dm2), which enables selective sensing of Al³⁺ in aqueous DMF were synthesized by a simplistic one-step condensation reaction of macrocyclic compounds. The probe me1 and dm2 characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR, LC-MS spectral techniques. The compounds as mentioned above subjected to FE-SEM with EDS and elemental color mapping. On addition of Al³⁺, the fluorescent probe me1 and dm2 induces turn-on responses in both absorption and sensing spectra by a PET mechanism. The receptor me1 and dm2 serve highly selective, sensitive and turn-on detection of Al³⁺. Further, they did not interfere with other cations present in biological or environmental samples. The detection limit is found to be 3μM and 5μM. From the view of cytotoxic activity, the ability of these compounds me1 and dm2 to inhibit the growth of KB cell lines examined. The chelating functionality of compounds me1 and dm2 examined for their inhibitory properties of KB cell, live cell images. The compounds me1 and dm2 subjected to theoretical studies by DFT-B3LYP invoking the 6-31G level of theory. The energy of the HOMO and LUMO has been established.