Identifying the stoichiometry of metal/ligand complex by coupling spectroscopy and modelling: a comprehensive study on two fluorescent molecules specific to lead
Résumé
Two new chemosensors for lead (II) were synthesized based on 5-((anthracen-9-ylmethylene) amino)quinolin-10-ol (ANQ): (10-(8-hydroxyquinolin-5-ylimino)methyl)anthracen-9-yl)methyl methacrylate (ANQ-MMA) and ((10-((4-vinylbenzoloxy)methyl)anthracen-9-yl)methyleneamino)quinoline-8-ol (ANQ-ST). Complexation of those molecules with Pb 2+ was studied at room temperature using UV-Visible absorption and fluorescence spectroscopies. Thanks to the UV-visible absorption spectroscopy it appeared that ANQ-MMA formed 1:1 and 1:2 complexes with lead (II) and ANQ-ST only 1:1 complex. For both molecules, the fluorescence excitation-emission matrices (EEM) signal intensity increased from 0 to 100 µmol.L-1 of lead (II) followed by a saturation for higher concentrations. The decomposition of the obtained EEMs gave a set of empiric fluorescent components that have been directly linked to the distribution of lead complexes obtained with the UV-visible absorption spectroscopy study. This correlation allowed to evidenced metal/ligand complex stoichiometry and emerge as a new method to identify empiric components. Moreover, the two ligands showed a promising selectivity for Pb 2+
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