A novel ratiometric and TURN-ON fluorescent coumarin-based probe for Fe(III)

Five coumarinic derivatives able to coordinate Fe(III) and exhibiting a ratiometric and TURN-ON fluorescence response, were prepared and tested. The derivative with -OCH3 substituent, exhibited a high fluorescence enhancement in the presence of Fe(III), Ga(III), Au(III) and Y(III). Thanks to the higher stability of the Fe(III) complexes, this molecule could be proposed as selective fluorescent sensor for the detection of Fe(III) in CH3CN and CH3CN:H2O (1:1, v/v) solutions, showing a linear response up to 35.0 µM Fe(III) concentration and a limit of detection of 2.4 µM Fe(III) concentration. Fluorescence response towards this ion was also tested on a solid surface with a simple cellulose paper strip test. The peculiarity of the proposed sensor lies on an easy and low-cost synthesis, a relevant ratiometric response and, deriving from a natural product, a low impact on the environment and its organisms.