On the analytical response of lead(II) selective electrodes using 1-aroyl-3,3-dimethylthioureas as ionophores: membrane analysis and quantum chemical calculations

Abstract

Solid-state Pb²⁺-ion selective electrodes (Pb²⁺-ISEs) based on liquid membranes using three 1-aroyl-3,3-dimethylthioureas as ionophores were developed. The receptors differ structurally in the aromatic ring of the 1-aroyl group and have been labeled as FDM, BDM, and TDM. The analytical performance of the constructed electrodes was studied by determining the calibration parameters. The electrodes showed Nernstian behavior with average sensitivities of 30.1, 31.5 and 26.6 mV/dec, as well as average lifetimes of 100, 60 and 7 days, respectively. Cd²⁺ and Cu²⁺ cations were interfering toward Pb²⁺ ions detection. The sensing membranes were studied by SEM-EDS and the results have suggested the formation of aggregates through time related to complex species Pb²⁺-aroylthioureas. Additionally, quantum chemical calculations were carried out at the B3LYP/6-311G(d,p) level of theory to compute the geometry, frontier molecular orbital energies and global reactivity parameters of the aroylthioureas in tributyl phosphate (TBP) as solvent mediator. Correlation studies between the receptor’s quantum chemical parameters and the experimental analytical response of the Pb²⁺-ISEs were addressed in order to clarify the differences observed in the analytical response of the constructed electrodes. The results support the chemical model of interaction between thioureas and Pb²⁺ ions through orbital control involving vacant d-orbitals of the metal ion and electrons from the HOMO of the organic molecule.

Graphical Abstract

Keywords:

• Aroylthioureas
• lead(II)
• ISEs
• membranes
• DFT

Disclosure statement

The authors declare that there is no potential conflict of interest arising from the direct applications of this research.

Additional information

Funding

This work was supported by the “Oficina de Gestión de Fondos y Proyectos Internacionales del Ministerio de Ciencia, Tecnología y Medio Ambiente de la República de Cuba" under Grant PN223LH010-028; the authors greatly thank the Shared Hierarchical Academic Research Computing Network (SHARCNET: www.sharcnet.ca) and Compute/Calcul Canadá.