Identifying the Stoichiometry of Metal/Ligand Complex by Coupling Spectroscopy and Modelling: a Comprehensive Study on Two Fluorescent Molecules Specific to Lead

William René; Madjid Arab; Katri Laatikainen; Stéphane Mounier; Catherine Branger; Véronique Lenoble

doi:10.1007/s10895-019-02405-0

Identifying the Stoichiometry of Metal/Ligand Complex by Coupling Spectroscopy and Modelling: a Comprehensive Study on Two Fluorescent Molecules Specific to Lead

J Fluoresc. 2019 Jul;29(4):933-943. doi: 10.1007/s10895-019-02405-0. Epub 2019 Jul 13.

Authors

William René^{1

2

3}, Madjid Arab², Katri Laatikainen⁴, Stéphane Mounier³, Catherine Branger⁵, Véronique Lenoble⁶

Affiliations

¹ MAPIEM Laboratory, University of Toulon, CS 60584, 83041, Toulon, Cedex 9, France.
² IM2NP Laboratory, University of Toulon, CS 60584, 83041, Toulon, Cedex 9, France.
³ MIO Laboratory, University of Toulon, CS 60584, 83041, Toulon, Cedex 9, France.
⁴ Laboratory of Computational and Process Engineering, Lappeenranta-Lahti University of Technology LUT, P.O. Box 20, FI-53851, Lappeenranta, Finland.
⁵ MAPIEM Laboratory, University of Toulon, CS 60584, 83041, Toulon, Cedex 9, France. branger@univ-tln.fr.
⁶ MIO Laboratory, University of Toulon, CS 60584, 83041, Toulon, Cedex 9, France. lenoble@univ-tln.fr.

PMID: 31300981
DOI: 10.1007/s10895-019-02405-0

Abstract

Two new chemosensors for lead (II) were synthesized based on 5-((anthracen-9-ylmethylene) amino)quinolin-10-ol (ANQ). ANQ was modified in the para position of the imine group via a methoxy link either with methylmethacrylate (ANQ-MMA) or styrene (ANQ-ST). Complexation of those molecules with Pb²⁺ 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 evidence metal/ligand complex stoichiometry and emerge as a new method to identify empiric components. Moreover, the two ligands showed a promising selectivity for Pb²⁺, turning them interesting probes for this hazardous metal.

Keywords: Fluorescent molecules; Lead; Metal/ligand complex; Modelling; Spectroscopy.