A Multi-Responsive Naphthalimide-Based "Turn-on" Fluorescent Chemosensor for Sensitive Detection of Trivalent Cations Ga3+, Al3+ and Cr3.

A new multifunctional chemosensor 1, (E)-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)-1H-benzo[de]isoquinoline-1,3(2H)-dione, based on naphtalimide and naphthaldehyde was developed, which showed the fluorescence responses to trivalent metal ions (Ga3+, Al3+ and Cr3+). Sensor 1 detected and differentiated selectively trivalent metal ions Ga3+, Al3+ and Cr3+ by fluorescence enhancement at different emissions. The association constant of Ga3+-2∙1 complex is the highest one among those of the organic chemosensors reported, to date. The sensing mechanisms for Ga3+, Al3+ and Cr3+ were explained by UV-vis titrations, Job plots, ESI-mass analyses and theoretical calculations.