DFT data to relate calculated LUMO energy with experimental reduction potentials of Cu(II)-β-diketonato complexes

Abstract

We present data on the computed lowest unoccupied molecular orbital energy ( E LUMO ) of two series of Cu(II)-β-diketonato complexes, calculated via density functional theory (DFT). These are correlated to experimental reduction potential data ( E pc ), obtained by cyclic voltammetry under different experimental conditions (solvent, working and reference electrodes). All calculations were done with the B3LYP functional in the gas phase. Knowledge of the influence of different ligands on the redox potential of copper complexes, as measured by DFT calculated energy data, are very useful. These theoretical correlations are vital in the further design of similar compounds, to be customized for specific applications. The correlations can be used to predict and fine-tune redox potentials prior to synthesis, saving experimental chemists time and laboratory expenses. Redox potentials influence the catalytic property of bis(β-diketonato)copper(II) compounds. New catalysts can therefore be customized with a specific reduction potential and catalytic activity. Further, the Cu(II/I) redox couple is a potential alternative as electrolyte for dye-sensitized solar cells [1] , [2] , [3] . The redox potential of the electrolyte can drastically affect the photovoltage output and should therefore be optimized for efficiency and durability. By adjusting the reduction potential via different ligands on the complex, the properties of copper dyes can be fine-tuned at molecular level. For more insight into the reported data, see the related research article “Synthesis, Characterization, DFT and Biological Activity of Oligothiophene β-diketone and Cu-complexes” published in Polyhedron [4] .

Electrochemical and Theoretical Modelled Reduction of β‐Diketone Inspired Chalcones

“…In molecular terms, this can be understood as the energy required to add an electron to a molecule. Experimental reduction potentials and DFT‐calculated LUMO energies often show correlation, namely E LUMO is inversely proportional to the experimental reduction potential [44,94–103] . Molecules with a higher, more positive reduction potentials (i. e., more favorable reduction) typically have lower‐energy LUMOs (easier to accept an electron or differently stated, has a higher electron affinity) calculated by DFT.…”

“…Experimental reduction potentials and DFT-calculated LUMO energies often show correlation, namely E LUMO is inversely proportional to the experimental reduction potential. [44,[94][95][96][97][98][99][100][101][102][103] Molecules with a higher, more positive reduction potentials (i. e., more favorable reduction) typically have lower-energy LUMOs (easier to accept an electron or differently stated, has a higher electron affinity) calculated by DFT. Reduction data obtained under the same experimental conditions as obtained for (1) and ( 2) are available for a series of βdiketones (ACN as solvent [69,70] ) and a series of 2-hydroxyphe-nones (DMSO as solvent [85,104,105] ), see data in Table 2.…”