Crown Ether Functionalized Barbituric Acid for Colorimetric Determination of Au³+

In this study, we report the successful synthesis of a novel benzo crown ether-functionalized barbituric acid derivative (receptor 3) as a colorimetric probe for detecting Au³⁺ ions in aqueous solutions. The receptor was synthesized using a straightforward Knoevenagel condensation between 4, 4’-diformyl dibenzo-15-crown-5 ether and barbituric acid in methanol at room temperature, yielding the product in good quantities. This receptor demonstrated excellent selectivity and sensitivity towards Au³⁺ ions over other common cations, enabling rapid visual detection without the need for advanced instrumentation. Upon interaction with Au³⁺, receptor 3 caused a distinct color change in the solution from colorless to violet, which could be observed with the naked eye. The detection limit of receptor 3 was calculated to be as low as 2.95×10⁻⁵ molL⁻¹, making it highly suitable for detecting trace amounts of Au³⁺ in real-world applications. The optical properties of the receptor were further characterized using various techniques, confirming its stability and efficacy in aqueous medium (DMSO+H₂O, 1:4 v/v). This newly developed sensor holds significant potential for practical applications, particularly in environmental monitoring and gold ion detection in industrial processes, offering a cost-effective and simple alternative to more complex detection methods.