Synthesis and evaluation of the chromo-fluorogenic recognition ability of imidazoquinoline derivatives toward ions

Four imidazoquinolines functionalized with different carbocycles and heterocycles have been synthesized and characterized. Acetonitrile solutions of the four receptors presented absorption bands in the 330-370 nm range. The four probes were also emissive with fluorescence bands in the 390-460 nm interval. In a first step, the chromo-fluorogenic behaviour of the four probes was evaluated in the presence of selected anions. Addition of F- induced the appearance of a new red-shifted absorption band together with a moderate quenching of the fluorescence in all four receptors. In a second step, the UV-visible and emission behaviour of the four receptors in the presence of cations was tested. Addition of Hg2+, Cu2+, Co2+, Fe3+, Fe2+, Zn2+, Pb2+, Cd2+, Cr3+ and Al3+ induced a similar optical change in all four receptors (appearance of a broad red-shifted absorption band together with a remarkable quenching of the emission band).Fundação para a Ciência e Tecnologia (Portugal) and FEDER-COMPETE for financial support through the Centro de Química – Universidade do Minho, Project PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302) and a Post-doctoral grant to R.M.F. Batista (SFRH/BPD/79333/2011). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, with funds from FCT. We are also grateful to the Instituto da Educação of Universidade do Minho for providing the laboratory infrastructure necessary for the development of this work