E. Regulska

Spectroscopic study of molecular structure, antioxidant activity and biological effects of metal hydroxyflavonol complexes.

Flavonols with varied hydroxyl substitution can act as strong antioxidants. Thanks to their ability to chelate metals as well as to donate hydrogen atoms they have capacity to scavenge free radicals. Their metal complexes are often more active in comparison with free ligands. They exhibit interesting biological properties, e.g. anticancer, antiphlogistic and antibacterial. The relationship between molecular structure and their biological properties was intensively studied using spectroscopic methods (UV-Vis, IR, Raman, NMR, ESI-MS). The aim of this paper is review on spectroscopic analyses of molecular structure and biological activity of hydroxyflavonol metal complexes.

Molecular structure and spectroscopic analysis of homovanillic acid and its sodium salt – NMR, FT-IR and DFT studies

The estimation of the electronic charge distribution in metal complex or salt allows to predict what kind of deformation of the electronic system of ligand would undergo during complexation. It also permits to make more precise interpretation of mechanism by which metals affect the biochemical properties of ligands. Theinfluence ofsodium cation on the electronic system of homovanillic acid was studied in this paper. Optimized geometrical structures of studied compounds were calculated by B3LYP/6-311++G(**) method. Mulliken, MK and ChelpG atomic charges were analyzed. The theoretical NMR and IR spectra were obtained. (1)H and (13)C NMR as well as FT-IR and FT-Raman spectra of studied compounds were also recorded and analyzed. The calculated parameters are compared with experimental characteristics of these molecules.

Theoretical (in B3LYP/6-3111++G** level), spectroscopic (FT-IR, FT-Raman) and thermogravimetric studies of gentisic acid and sodium, copper(II) and cadmium(II) gentisates.

The DFT calculations (B3LYP method with 6-311++G(d,p) mixed with LanL2DZ for transition metals basis sets) for different conformers of 2,5-dihydroxybenzoic acid (gentisic acid), sodium 2,5-dihydroxybenzoate (gentisate) and copper(II) and cadmium(II) gentisates were done. The proposed hydrated structures of transition metal complexes were based on the results of experimental findings. The theoretical geometrical parameters and atomic charge distribution were discussed. Moreover Na, Cu(II) and Cd(II) gentisates were synthesized and the composition of obtained compounds was revealed by means of elemental and thermogravimetric analyses. The FT-IR and FT-Raman spectra of gentisic acid and gentisates were registered and the effect of metals on the electronic charge distribution of ligand was discussed.

Hydroxyflavone metal complexes - molecular structure, antioxidant activity and biological effects

High content of hydroxyflavones in fruits, vegetables, cereals and herbs makes them a common component of the human diet. Because of their antioxidant, antiviral, antibacterial, anti-inflammatory, anticancer properties they still pay an attention of many scientific centers. Hydroxyflavones may form complexes with metal cations, and their chelating properties differ significantly depending on the number and position of hydroxyl substituents in the ring. Synthesis of new complexes of hydroxyflavones allows for improvement biological properties, stability, water-solubility, hydrophilicity, bioavailability comparing with the parent hydroxyflavones. It expands the applicability of hydroxyflavones as food additives, diet supplements, preservatives or drug. This paper reviews on the procedures of synthesis of metal complexes with hydroxyflavones, their molecular structure, mode of coordinations, spectroscopic properties and their biological activity. The dependency between the biological activity of these compounds and their molecular structure is discussed.

Influence of alkaline earth metals on molecular structure of 3-nitrobenzoic acid in comparison with alkali metals effect.

The influence of beryllium, magnesium, calcium, strontium and barium cations on the electronic system of 3-nitrobenzoic acid was studied in comparison with studied earlier alkali metal ions. The vibrational FT-IR (in KBr and ATR techniques) and (1)H and (13)C NMR spectra were recorded for 3-nitrobenzoic acid and its salts. Characteristic shifts in IR and NMR spectra along 3-nitrobenzoates of divalent metal series Mg→Ba were compared with series of univalent metal Li→Cs salts. Good correlations between the wavenumbers of the vibrational bands in the IR spectra for 3-nitrobenzoates and ionic potential, electronegativity, inverse of atomic mass, atomic radius and ionization energy of metals were found for alkaline earth metals as well as for alkali metals. The density functional (DFT) hybrid method B3LYP with two basis sets: 6-311++G** and LANL2DZ were used to calculate optimized geometrical structures of studied compounds. The theoretical wavenumbers and intensities of IR spectra as well as chemical shifts in NMR spectra were obtained. Geometric aromaticity indices, atomic charges, dipole moments and energies were also calculated. The calculated parameters were compared to experimental characteristic of studied compounds.

The FT-IR, FT-Raman, 1H and 13C NMR study on molecular structure of sodium(I), calcium(II), lanthanum(III) and thorium(IV) cinnamates

In this work the effect of sodium(I), calcium(II), lanthanum(III) and thorium(IV) ions on the electronic structure of cinnamic acid (phenylacrylic acid) was studied. In this research: infrared (FT-IR), Raman (FT-Raman), nuclear magnetic resonance ( 1 H, 13 C NMR) were used. In the series of Na(I) → Ca(II) → La(III) → Th(IV) cinnamates: (1) systematic shifts of several bands in the FT-IR and FT-Raman spectra, and (2) regular chemical shifts of protons 1 Ha nd 13 C nuclei were observed.

Experimental and theoretical study of molecular structure of beryllium, magnesium, calcium, strontium and barium 4-nitrobenzoates.

The influence of alkaline earth metal ions on the electronic system of 4-nitrobenzoic acid was studied in this paper. The vibrational (FT-IR) and NMR ((1)H and (13)C) spectra were recorded for 4-nitrobenzoic acid (4-nba) and its salts (4-nb). The assignment of vibrational spectra was done. Some shifts of band wavenumbers in alkaline earth metal 4-nitrobenzoates spectra were observed in the series from magnesium to barium salts. Good correlations between wavenumbers of the vibrational bands in the IR spectra of studied salts and ionic potential, electronegativity, inverse of atomic mass, ionic radius and ionization energy of studied metals were found. The regular changes in the chemical shifts of protons ((1)H NMR) and carbons ((13)C NMR) in the series of studied salts were also observed. Optimized geometrical structures of studied compounds were calculated by B3LYP method using 6-311++G(**) as well as LANL2DZ basis sets. Theoretical wavenumbers and intensities in IR and chemical shifts in NMR spectra were also obtained. The calculated parameters were compared with experimental data of studied compounds.

Spectroscopic (FT-IR, Raman, NMR) and DFT Quantum Chemical Studies on Phenoxyacetic Acid and Its Sodium Salt

FT-IR, Raman, and NMR spectra of phenoxyacetic acid and its sodium salt were recorded and analyzed. Optimized geometrical structures of studied compounds were calculated by B3LYP/6-311

The effect of alkali metal ions on the electronic structure of p-anisic acid 1

FT-IR (in solid state and solution), FT-Raman, UV and 1 H, 13 C NMR spectra of p-methoxybenzoic (p-anisic) acid and lithium, sodium, potassium, rubidium and caesium p-methoxybenzoates (p-anisates) were registered, assigned and ana- lyzed. The structures of anisic acid and Li, Na and K p-anisates were optimised at the B3LYP/6-311++G** level. The IR spectra and NPA, ChelpG and MK atomic charges were calculated. The effect of metal ions on the electronic charge distribu- tion in ligand was discussed.

Calcium complex of 2,5-dihydroxybenzoic acid (gentisic acid): synthesis, crystal structure, and spectroscopic properties

Abstract The synthesis, crystal structure, and spectral characteristics (IR, Raman, and 1H and 13C NMR) of a monomeric hexa(aqua)calcium compound, viz. [Ca(C7H5O4)2(H2O)6]·H2O (C7H5O4 = 2,5-dihydroxybenzoate), are reported. The central Ca(II) located on a twofold axis is eight coordinate in an approximate square antiprismatic environment, bonded to two monodentate 2,5-dihydroxybenzoate ligands via the carboxylate oxygen, and six waters. The adjacent monomeric units are linked with the aid of several O–H⋯O hydrogen bonds.