Colorimetric metal ion (II) Sensors Based on imine boronic esters functionalized with pyridine

Paola Sánchez-Portillo (1) , Aime Hernández-Sirio (1) , Carolina Godoy-Alcántar (1) , Pascal G. Lacroix (2) , Vivechana Agarwal (3) , Rosa Santillán (4) , Victor Barba (1) , Aime Hern´ C Andez-Sirio , Carolina D Godoy-Alc´a , Pascal G Lacroix , Vivechana A Garwal

1 CIQ / UAEM - Centro de Investigaciones Químicas [Morelos]
2 LCC - Laboratoire de chimie de coordination
3 UAEM - Universidad Autonoma del Estado de Morelos
4 Centro de Investigacion y de Estudios Avanzados del IPN

The one-step synthesis of three imine boronic esters functionalized with pyridyl groups is described (1a-1c). The presence or absence of a methyl group affects the whole conformation, being bent “L” or linear as determined by X-ray crystal diffraction. C–H⋯O, C–H⋯N, C–H⋯F and C–H … π hydrogen bond interactions support 2D supramolecular arrangements. Ligands were tested as metal ion (M2+) sensors in solution. The addition of metal cations (Fe2+, Co2+ and Cu2+) to 1a using methanol as solvent, showed significant color changes (purple, orange and green, respectively), while for metal cations Ni2+, Zn2+, Cd2+ cations no color changes were observed. The sensitivity of compound 1a towards Fe2+, Co2+ and Cu2+ was monitored by UV–Vis spectroscopy, where the presence of Fe2+ produces new bands at 360 and 566 nm. For Co2+ and Cu2+ a remarkable intensity increase was observed at 290 nm band and new bands appear at 340 and 462 nm, respectively. The stoichiometry of the complexes 1a-Fe2+, 1a-Co2+ and 1a-Cu2+ was determined by Job's plots being 1:3 (metal:ligand, complex [Fe (1a)3]2+), in contrast with the stoichiometry 1:1 observed for 1b-Fe2+. In fact, the computed ΔG formation associated value showed a strong stabilization for the complex [Fe (1a)3]2+ (−65.5 kcal/mol) in comparison with the possible complex [Fe (1b)3]2+ (−29.7 kcal/mol). Detection limits are in the mM range (determined by UV–Vis) and μM range (determined by Fluorescence). An analogous bis-bidentate derivative (2a) also shows similar behavior but stoichiometric interaction changes to 2:3 (metal:ligand) and detection limits are in the mM range obtained by UV–Vis and Fluorescence techniques.

Mots clés: Imines; Selective sensors; Colorimetric chemosensors; Boronic esters; Imines

Domaines: Chimie de coordination

Paola Sánchez-Portillo, Aime Hernández-Sirio, Carolina Godoy-Alcántar, Pascal G. Lacroix, Vivechana Agarwal, et al.. Colorimetric metal ion (II) Sensors Based on imine boronic esters functionalized with pyridine. Dyes and Pigments, 2021, 186, pp.108991. ⟨10.1016/j.dyepig.2020.108991⟩. ⟨hal-03108961⟩