Understanding the antioxidant activity of flavonoids is important to investigate their biological activities as well as to design novel molecules with low toxicity and high activity. Aromaticity is a chemical property found in cyclic structures that plays an important role in their stability and reactivity, and its investigation can help us to understand the antioxidant activity of some heterocyclic compounds. In the present study, we applied the density functional theory (DFT) to investigate the properties of seven flavonoid structures with well-reported antioxidant activity: flavan, anthocyanidin, flavanone, flavonol, isoflavone, flavone, and flavan-3-ol. Conformational, structural, magnetic, and electronic analyses were performed using nuclear magnetic resonance, ionization potentials, electron affinity, bond dissociation energy, proton affinity, frontier molecular orbitals (highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO)), and aromaticity through nucleus-independent chemical shifts to analyze these seven flavonoid structures. We revised the influence of hydroxyl groups on the properties of flavonoids and also investigated the influence of the aromaticity of these seven flavonoids on the antioxidant activity.

Analysis of Conformational, Structural, Magnetic, and Electronic Properties Related to Antioxidant Activity: Revisiting Flavan, Anthocyanidin, Flavanone, Flavonol, Isoflavone, Flavone, and Flavan-3-ol.

Synthesis, crystal structures and antimicrobial activity of dimeric copper(II) complexes with 2-hydroxyphenyl-ethylidene-dithiocarbazates

Synthesis, theoretical calculation and anticancer activity of 4,6-diacetylresorcinol-dithiocarbazates and their Copper(II) complexes

DFT analysis, spectroscopic study and biological activity of a newly synthesized benzoylhydrazone binuclear Cu(II) complex.

Diversities in the chelation of aroylhydrazones towards cobalt(II) salts: Synthesis, spectral characterization, crystal structure and some theoretical studies

Copper(II) and zinc(II) complexes with Hydrazone: Synthesis, crystal structure, Hirshfeld surface and antibacterial activity

Hydrazone-derived copper(II) coordination polymer as a selective liquid-phase catalyst: Synthesis, crystal structure and performance towards benzyl alcohol oxidation

This work describes the synthesis and the crystal structure of a copper(II) complex – [Cu(HL)(NO3)2]·H2O – based on 2-acetylpyridine-benzoylhydrazone ligand (HL). In the complex, copper(II) is five-coordinate with two nitrate ligands and a tridentate NNO-donor. The copper center has square pyramidal geometry with an axial nitrate and the equatorial positions occupied by another nitrate and the hydrazone. Besides X-ray studies, the complete structural characterization includes elemental analysis, IR, and UV–vis spectroscopy. Plane wave and localized basis set calculations support the distorted square pyramidal geometry. Theoretical calculations using several DFT functionals were used to study the performance of functionals for this complex. Solvent effect was studied on optimized geometries allowing better support to its spectroscopic data. Noncovalent π⋯π stacking interactions were also analyzed.

New Cu(II) complex with acetylpyridine benzoyl hydrazone: experimental and theoretical analysis

Two novel Cu(I) complexes with the 2-acetylpyridine-N(4)-phenyl semicarbazone (HL) ligand, [CuCl (HL)(PPh3)]∙CH3CN (1) and [CuBr (HL)(PPh3)] (2), were investigated by single-crystal X-ray analysis, Hirshfeld surface, and physicochemical and spectroscopic methods. In both cases, the Schiff base was coordinated by the bidentate ligand via the pyridine nitrogen and the iminic nitrogen atoms. A molecule of triphenylphosphine and a halide ion (Cl− or Br−) completed the coordination sphere of the metal centers. The geometry around the copper atoms was distorted tetrahedral geometry. The secondary coordination sphere of Cu(I) is pentacoordinated and has weak interactions Cu···O of 2.906(1) A and 2.783(1) A. The 3D Hirshfeld surface and the 2D fingerprint plots of the complexes were analyzed quantitatively to verify the presence of intermolecular interactions. By their crystal structure of (2), it is possible to observe π···π stacking interactions between the pyridyl and phenyl rings from HL and also between phenyl rings and the triphenylphosphine ligands forming a 1D network. The biological activity of the Cu(I) salts, the free semicarbazone, and its Cu(I) complexes was evaluated against human cancer cell lines MCF-7 and nontumor cell lines PBMC.

Two Cu(I) complexes based on semicarbazone ligand: synthesis, crystal structure, Hirshfeld surface and anticancer activity evaluation against human cell lines

Pedro H.O. Santiago

Papers

Copper(II) and zinc(II) complexes with Hydrazone: Synthesis, crystal structure, Hirshfeld surface and antibacterial activity

DFT analysis, spectroscopic study and biological activity of a newly synthesized benzoylhydrazone binuclear Cu(II) complex.

Hydrazone-derived copper(II) coordination polymer as a selective liquid-phase catalyst: Synthesis, crystal structure and performance towards benzyl alcohol oxidation

New Cu(II) complex with acetylpyridine benzoyl hydrazone: experimental and theoretical analysis

Two Cu(I) complexes based on semicarbazone ligand: synthesis, crystal structure, Hirshfeld surface and anticancer activity evaluation against human cell lines