A novel ratiometric and turn-on fluorescent coumarin-based probe for Fe(iii)

Five coumarin derivatives, able to coordinate Fe(iii) and exhibit a ratiometric and turn-on fluorescence response, were prepared and tested. The derivative with the -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 a 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 mu M Fe(iii) concentration and a limit of detection of 2.4 mu M Fe(iii) concentration. The 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 in its easy and low-cost synthesis, relevant ratiometric response and, since it is derived from a natural product, low impact on the environment and its organisms.