QUANTUM-CHEMICAL CALCULATIONS OF CURCUMIN AND SOME METAL COMPLEXES BASED ON IT

• Date: 2025
• Main Authors: Horbenko , Artur, Trunova , Olena
• Format: Article
• Language: English
• Published: V.I.Vernadsky Institute of General and Inorganic Chemistry 2025
• Online Access: https://ucj.org.ua/index.php/journal/article/view/707
• Journal Title: Ukrainian Chemistry Journal

Using the semi-empirical PM7 method in combination with the SPARKLE model, the structure of isomeric forms and the energetics of conformational and tautomeric transformations of the curcumin molecule were calculated, the geometry of the ligandand transition metal complexes (Zn(II), Dy(III), Ag(I)) based on it were optimized: ZnCur2∙2H2O, ZnCur2∙Phen, DyСur3∙3H2O, AgZnСur3∙H2O∙AcOH. The energetic characteristics of the compounds were calculated, described and analyzed, such as the total energy of the molecules, the enthalpy of formation, the dipole moment, the energies of the highest occupied molecular orbital (ЕHOMO) and the lowest unoccupied molecular orbital (ЕLUMO), the ionization potential, the electron affinity, the rigidity, the softness and the main bondlengths and the charges on the atoms. Based on the calculated values of the heat of formation, the energy gap ∆E and the overall rigidity, it is assumed that the enol form of the curcumin molecule is more energetically favorable and more chemically reactive compared to the ketoform. In addition, the stability of Curenol is additionally due to the presence of intramolecular hydrogen bonding. Curcuminate metal complexes, regardless of the metal, arecharacterized by a non-planar structure in which the curcumin ligands are coordinated bidentately-chelately through the β-diketone fragment with the formation of 6-membered metalcycles [OМOCCC]. Analysis of the values ​​of the enthalpy of formation of the complexes showed that the process of molecule formation is exothermicand ΔH increases in the series AgZnСur3∙H2O∙AcOH > DyCur3∙3H2O > ZnCur2∙2H2O > ZnCur2∙Phen. The least stable is the ZnCur2∙Phen complex, which is also confirmed by the smallest energy gap value (ΔE = -6.66 eV). It is shown that in the heterometallic complex AgZnСur3∙H2O∙AcOH there is a tendency to form a more compact structure, which may be due to the formation of weak hydrogen bonds between the carbonyl oxygen atoms of curcumin molecules coordinated to the Zn and Ag atoms.