A naphthalene exciplex based Al3+ selective on-type fluorescent probe for living cells at the physiological pH range: experimental and computational studies

Abstract

2-((Naphthalen-6-yl)methylthio)ethanol (HL) was prepared by one pot synthesis using 2-mercaptoethanol and 2-bromomethylnaphthalene. It was found to be a highly selective fluorescent sensor for Al³⁺ in the physiological pH (pH 7.0–8.0). It could sense Al³⁺ bound to cells through fluorescence microscopy. Metal ions like Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Hg²⁺, Cr³⁺ and Pb²⁺ did not interfere. No interference was also observed with anions like Cl⁻, Br⁻, F⁻, SO₄²⁻, NO₃⁻, CO₃²⁻, HPO₄²⁻ and SCN⁻. Experimentally observed structural and spectroscopic features of HL and its Al³⁺ complex have been substantiated by computational calculations using density functional theory (DFT) and time dependent density functional theory (TDDFT).