Synergy Effects in Heavy Metal Ion Chelation with Aryl- and Aroyl-Substituted Thiourea Derivatives.

Ransel Barzaga,Fernando Aguilar-Galindo,Sergio Díaz-Tendero,Lucia Lestón-Sánchez,Osvaldo Estévez-Hernández

doi:10.1021/acs.inorgchem.1c01068

Ransel Barzaga, Fernando Aguilar-Galindo + Show 3 more

Open Access

https://doi.org/10.1021/acs.inorgchem.1c01068

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Abstract

Detection and removal of metal ion contaminants have attracted great interest due to the health risks that they represent for humans and wildlife. Among the proposed compounds developed for these purposes, thiourea derivatives have been shown as quite efficient chelating agents of metal cations and have been proposed for heavy metal ion removal and for components of high-selectivity sensors. Understanding the nature of metal-ionophore activity for these compounds is thus of high relevance. We present a theoretical study on the interaction between substituted thioureas and metal cations, namely, Cd2+, Hg2+, and Pb2+. Two substituent groups have been chosen: 2-furoyl and m-trifluoromethylphenyl. Combining density functional theory simulations with wave function analysis techniques, we study the nature of the metal-thiourea interaction and characterize the bonding properties. Here, it is shown how the N,N'-disubstituted derivative has a strong affinity for Hg2+, through cation-hydrogen interactions, due to its greater oxidizing capacity.

Highlights

One of the processes to eradicate such pollutants is chemical remediation, which consists of the complexation of the ions using chelating ligands.34−38 Thiourea derivatives are promising chelating agents of metal cations that have been proposed for heavy metal ion removal.39−51 Both for sensing and for removal reasons, understanding heavy metal−ionophore activity by organic compounds is of high relevance.52−54 In this context, several studies have focused on metal complexes with thiourea derivatives
We have theoretically studied the complexation of three metal cations, namely, Cd(II), Hg(II), and Pb(II), with four thiourea molecules: [1] bare thiourea, [2] 2-furoyl thiourea, [3] m-triflouromethylphenyl thiourea, and [4]N-(2furoyl)-N′-(trifluoromethyl)phenylthiourea; both the thione and the thiol forms of these compounds have been considered
Several isomers were computed for each compound, giving a total of 479 structures

Summary

Introduction

Among the most toxic environmental pollutants are heavy metals.− In addition to their toxicity, their persistence in the environment, since they are non-biodegradable; their tendency to biomagnificate; and their bioaccumulative nature make them contaminants whose detection and removal are essential.− Several kinds of heavy metal-detection sensors have been developed, such as biosensors,− electrochemical sensors,− nanomaterial-based sensors,− and optical sensors.− Today, intense research activity is focused on increasing both the sensitivity and selectivity in detection by these devices.− In this way, thiourea derivatives have been developed as a new type of organic ionophores for heavy metal ion selective electrodes. One of the processes to eradicate such pollutants is chemical remediation, which consists of the complexation of the ions using chelating ligands.− Thiourea derivatives are promising chelating agents of metal cations that have been proposed for heavy metal ion removal.− Both for sensing and for removal reasons, understanding heavy metal−ionophore activity by organic compounds is of high relevance.− In this context, several studies have focused on metal complexes with thiourea derivatives. The investigation of interactions between metallic cations and organic compounds has attracted huge interest in the last few decades, where an important activity has been developed by means of computational chemistry.− In many studies, the theory has been combined with experiments, typically carried out with mass spectrometry techniques.− The nature of the metal ion−molecule interaction, the reactivity of the new compounds, and the change in structural and spectroscopic properties of the organic molecules upon ion complexation are among the most important aspects investigated in these studies. We focus on the interactions of these cations with the canonical thiourea, mainly characterizing the metal− sulfur and metal−nitrogen bonds. In this part of the study, we have performed molecular dynamics simulations allowing us to evaluate the evolution of the complexes over time. We have chosen as substituents 2-furoyl and m-trifluoromethylphenyl, inspired by the studies of Otazo-Sań chez and collaborators. These

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