TY  - JOUR
AU  - Hirayama, Ayumu
AU  - Narita, Mao
AU  - Ito, Shota
AU  - Nakane, Daisuke
AU  - Hosny, Shimaa
AU  - Akitsu, Takashiro
PY  - 2026
DA  - 2026/09/13
TI  - Assessing the Limitations of DFT and TD-DFT Calculations for Spectroscopic and Electrochemical Properties of Azo-Amino Acid Schiff Base Cu(II) Complexes
JO  - Recent Progress in Materials
SP  - 008
VL  - 08
IS  - 03
AB  - In this study, we assessed the reliability and limitations of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) in predicting the spectroscopic and electrochemical properties of four azo-amino acid Schiff-base Cu(II) complexes by comparing calculated ultraviolet-visible (UV-vis) absorption and circular dichroism (CD) spectra and reduction potentials with experimental data obtained from spectroscopic measurements and cyclic voltammetry (CV). The optimized coordination geometries were generally close to square planar, whereas the phenylalanine complex showed the largest distortion, with a τ4 value of 0.204. TD-DFT reproduced some major features of the experimental UV-vis and CD spectra qualitatively; however, the calculated UV-vis bands were generally shifted toward shorter wavelengths, whereas the CD spectra showed discrepancies in wavelength, intensity, and sign. In particular, the positive experimental CD features in the approximately 300-325 nm region were predicted with the opposite sign for all four complexes. For the Cu(II)/Cu(I) couples, the calculated reduction potentials differed by 0.21-0.32 V between the two computational protocols, and the predicted ordering of reducibility also changed between the two protocols. Moreover, this ordering was inconsistent with the trend inferred from the lowest unoccupied molecular orbital energies. These results demonstrate that agreement in spectral peak positions or frontier-orbital trends alone is insufficient to establish the quantitative reliability of DFT and TD-DFT predictions for transition-metal complexes. Property-specific benchmarking and careful treatment of structural relaxation, solvation, and possible conformational variability are therefore required when applying these methods to such systems in solution.
SN  - 2689-5846
UR  - https://doi.org/10.21926/rpm.2603008
DO  - 10.21926/rpm.2603008
ID  - Hirayama2026
ER  -