Conformational analysis, molecular structure, relative stability, and complete vibrational assignment of bis(2,2,6,6-tetramethylheptane-3,5-dionato)copper(II), Cu(tmhd)2, were investigated by density functional theory (DFT), Natural Bond Orbital (NBO) theory and Atoms-in-Molecules (AIM) analysis. Fourier transform-Raman and IR spectra of this complex have been also recorded. The theoretical and experimental methods used to investigate the substitution effects of methyl groups by t-butyl (t-but) on the structure and stability of complex. To explore the substitution effects, the structure and vibrational spectra of Cu(tmhd)2 compared with copper(II) acetylacetonate, Cu(acac)2. A complete assignment of the observed band frequencies has been done. Comparing of observed and calculated vibrational spectra suggests coexisting of two conformers in the sample. All theoretical and vibrational spectroscopic results are consisting with a stronger metal–oxygen bond in Cu(tmhd)2 than in Cu(acac)2.

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