Abstract
A computational study on three related derivatives of 5-[(azulen-1-yl)methylene]-2-thioxoimidazolidin-4-one was conducted using density functional theory by calculating a series of molecular descriptors and properties of their optimized geometries (electrostatic and local ionization potentials, molecular frontier orbitals, etc.). Thermodynamic properties (zero-point energy, enthalpy, constant volume heat capacity, entropy and Gibbs energy) for these derivatives have been calculated and related to ligands electrochemical behavior. Reduction and oxidation potentials have been correlated to their calculated energy levels for LUMO and HOMO orbitals. Chemically modified electrodes based on these derivatives have been tested in view of heavy metal ions recognition, and their detection limits have been correlated to the calculated values of electron affinity.
Highlights
Azulenes have a push-pull structure, with a five-member cyclic moiety connected to a seven-member cyclic moiety
The molecular structures comprise two coplanar cycles (I and II) and the cycle imidazolidine ring (III), which can be rotated around C14-C13 bond, showing a small deviation from co-planarity given by the small values of the dihedrals (H7, C14, C13, C12) and (C3, C14, C13, N2)
Chemical reactivity descriptors were predicted from the Density functional theory (DFT) calculations
Summary
Azulenes have a push-pull structure, with a five-member cyclic moiety (electron-rich) connected to a seven-member cyclic moiety (electron-poor). AZULENE LIGANDS FOR HEAVY METAL IONS DETECTION electrooxidations and irreversible or quasi-reversible reductions when polarized at anodic or cathodic potentials, respectively [1] Due to their low oxidation potential, they can lead to modified electrodes which could be used to build new electrochemical sensors. Modified electrodes have been prepared from these ligands under similar conditions and used for heterogeneous recognition Their detection limits for some heavy metal ions (Hg, Pb, Cd, Cu) have been evaluated in order to be correlated to their molecular structural descriptors. The accumulation of heavy metal ions has been performed in the assay solutions containing heavy metal ions in different concentrations (starting from 10-10 to 10-4) for 20 minutes under magnetic stirring This step has been followed by the stripping of the accumulated metal ions, after a reduction at -1.2 V for 120 s, in CV or DPV anodic scans with a scan rate of 0.01 V/s. The stripping currents for Cd, Pb, Cu, and Hg currents have been evaluated for each concentration
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