What is it about?
A Born-Haber thermodynamic cycle was used to determine the redox potential in a series of rhenium (III) clusters of the form [Re6(μ3-Q8)X6]4- where Q = S2-, Se2- and X = F-, Cl-, Br-, I-, CN-, NC-, SCN-, NCS-, OCN-, NCO-. Frequency analysis, relativistic and solvent effects were considered to estimate the free energy of the reversible process ReIII6/ReIII5ReIV at DFT level of theory. All the redox potentials were reported with respect to the standard hydrogen electron (SHE) and show good agreement with the available experimental results. In general, the molecular orbitals involved in the redox process were localized in the cluster core, Re6(μ3-Q8)2+, and therefore the peripheral ligands act only as a modifier of the crystal-field strength, thus influencing the energetic of the frontier molecular orbital splitting. Additionally, the theoretical approach was validated by an experimental protocol to study the electrochemical behavior of [Re6(μ3-Se8)I6]3-cluster, where an important first reversible reduction process was found at E1/2 = +0.47 V (SHE), which is in good agreement with the value predicted theoretically.
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Why is it important?
The redox potential of a series of eighteen [Re6(μ3-Q)8]2+ cluster type, where Q = S2-, Se2- , with via an optimization and frequency analysis at BP86/TZ2P level of theory. Also, the solvation energies were estimated using a conductor like screening model (COSMO) with the parameters of acetonitrile.
Perspectives
Although, there is not experimental data for the comparison of several of the calculated compounds, this corresponds to a first approximation of calculation of redox potentials by this method, in which a Born-Haber thermodynamic cycle was considered involving the reduced/oxidized species. According to the results obtained in the measurement of the oxidation potential for [Re6(μ3-Se)8I6]3- cluster (0.47 V) we can confirm the reliability of the computational DFT approach employed, because for the same compounds, the calculated value was 0.28 V. Nevertheless, this approximation provides good fit with the few experimental data reported in literature and measure in this work. The purpose of performing this type of thermodynamic reduction potential in order to be able to cycle, is due to the importance of oxidation and predict the chemical reactivity and have knowledge about the stability of these compounds. Finally, it is of great importance the study of computational methodologies that make a prediction of potential redox in rhenium cluster in order to obtain a better correlation with experimental data.
Dr Alexander Carreño
UNAB
Read the Original
This page is a summary of: Electrochemical behaviors and relativistic DFT calculations to understand the terminal ligand influence on the [Re6(μ3-Q)8X6]4− clusters, New Journal of Chemistry, January 2018, Royal Society of Chemistry,
DOI: 10.1039/c7nj05114j.
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