Derivative of clove oil used as a chemosensor for the colorimetric and fluorometric detection of Al3+: crystal structure description and live cell imaging

Abstract

Eugenol, which is popularly known as clove oil, has been treated as an important natural ingredient from ancient times owing to its versatile pharmacological properties. To date, the use of derivatives of clove oil as chemosensors for the detection of metal ions has been unexplored. Herein, an eugenol-rhodamine-based dual sensor (colorimetric and fluorometric), H₃L, was synthesized via the condensation reaction between N-(rhodamine-6G)lactam-hydrazine and eugenol-5-aldehyde, which selectively detected Al³⁺ in an HEPES buffer at pH = 7.4 (MeOH : H₂O = 9 : 1, (v/v)). Crystal structure of the chemosensor (H₃L) validated the occurrence of a Schiff base condensation reaction and formation of a closed spirolactam ring. Upon excitation at 500 nm, H₃L generated a pink coloration and strong fluorescence enhancement (∼138 times at 552 nm) in the presence of Al³⁺. ESI-MS value, NMR, and IR spectroscopic data suggested a 1 : 1 H₃L and metal ion binding stoichiometry. Strong association constant (2.01 × 10⁵ M⁻¹) and low value of limit of detection (LOD) (2.82 × 10⁻⁶ M) of H₃L against Al³⁺ indicate its practical applications in cell imaging studies. Furthermore, theoretical calculations were performed to support the fluorescence enhancement mechanism and metal-chemosensor coordination.