Benchmarking CuₙO (n = 1, 2) complexes via ab initio methods: structural, electronic, and thermodynamic insights with biochemical relevance.

contextCopper is an essential trace element that plays a central role in redox chemistry and electron transfer processes in biological systems. To gain a deeper understanding of the electronic behavior of copper species, we carried out a comparative evaluation of the Cu

methodsThis study employed density functional theory (DFT) alongside thermodynamic cycles to assess the stability of Cu(Indo)₂ and Cu₂(Indo)₄ complexes in ethanol solution. To select suitable computational methods, a benchmark was conducted using Cu(II)/acetate complexes as reference systems. A total of fifteen DFT functionals-BPW91, PBE, B97D, revTPSS, M06-L, M11-L, B3LYP, BHandHLYP, PBE0, ωB97XD, APDF, M06, M06-2X, M06-HF, and TPSSh-were tested in combination with four basis sets: Def2-SVP, Def2-TZVP, 6-31 + G(d,p), and 6-311 + G(d,p). The most reliable functional-basis set combinations were then applied to the copper-indomethacin complexes. In addition, electronic and structural properties of Cu₂ and CuO-such as ionization potentials, electron affinities, vibrational frequencies, equilibrium bond lengths, and spin or magnetic coupling constants-were calculated. Computational results were validated through comparison with available experimental data.