USING QUANTUM-CHEMICAL PARAMETERS FOR PREDICTING ANTIRADICAL (HO•) ACTIVITY OF RELATED STRUCTURES CONTAINING A CINNAMOIL FRAGMENT. IV. STRUCTURE-ACTIVITY RELATIONSHIP BETWEEN UNSATURATION INDICES AND FLAVONE DERIVATIVES WITH FLOROGLUCIN RING “A”

The quantum-chemical parameters of 52 derivatives related to flavanones, flavanonoles, flavones and flavonoles with a phloroglucinic type of the A ring and containing electron-donating substituents in the B ring were studied.The aim is the analysis of the dynamics of changes in the electron density, bond numbers, free valence indices and unsaturation indices on carbon atoms C-7 → C-8 of the vinyl group of the main conjugation chain in relation to the position and number of substituents in the “B” ring and the type of the pharmacological activity.Materials and methods. The quantum-chemical parameters of the 4 analyzed groups of the compounds, have been calculated by the semi-empirical method PM7 (WinMopac 2016 program) on the workstation with an Intel Xeon E5-1620 3.5 GHz processor, 20 GB of RAM.Results and discussion. When comparing the quantum chemical parameters of the analyzed compounds, it was established that when the C-7 → C-8 multiple bond is formed, the free valency and unsaturation indices increase on both carbon atoms of the vinylene group in flavones and flavonols compared to the corresponding flavanones and flavanonols. This is explained by the fact that the value of the bond numbers Nµ on these atoms, on the contrary, decreases (Fµ = 4.732-Nµ). The transition from flavanone to flavone is accompanied by the formation of a vinyl group C-7 → C-8, and therefore both atoms from the sp3-hybridized state go into the sp2-state. The consequence of this transformation is a change in the electronegativity value and an increase in the unsaturation index of C-7 and C-8 atoms: C sp3 = 2.5; Csp2 = 2.8. At the same time, the transition from flavanone to flavone leads to the formation of a conjugated system with the participation of π-electrons of the aromatic system “B”, C-7, C-8 atoms and the carbonyl group, which is commonly called the “main conjugation chain”. These structural changes, namely, the transition from a less oxidized flavanone to a more oxidized flavone, contribute to a decrease in the electron density on C-7 and C-8 atoms, and an increase in the total unsaturation of the molecules in general. Mulliken charges on C-7 of all groups of compounds are characterized by a positive value. As for the carbon atoms of the B fragment, the following features are revealed here: in the presence of one substituent -OH or -OCH3 on the carbon atom to which the substituent is bounded, the Mulliken charge is positive; if there are two substituents in the B ring -OH or -OCH3, as well as two -OCH3 groups, then the carbon atoms bonded to the indicated substituents also have a positive Mulliken charge; in the case of trihydroxy substituted in the C-2, C-3 and C-4 B ring, all three carbon atoms are characterized by a positive Mulliken charge; if there are methoxy groups in positions C-2, C-3 and C-4, then the positive Mulliken charge is concentrated only on C-2 and C-4 atoms, and on C-3 atom this charge has a negative value.Conclusion. The above data on the quantum-chemical parameters of the main conjugation chain indicate that the transition of C-7 and C-8 atoms to the sp2-hybrid state, leads to a decrease in the electron density and a decrease in the bond numbers, with a simultaneous increase in the indices of unsaturation and free valence on these atoms. Thus, the trigger mechanism of the anti-radical activity, primarily with respect to the HO • radical, is determined by the fact that this particle, electrophilic in its properties, will attach in the C-8 atom during an initial attack.

NEW 3,5-DISUBSTITUTED 2,6-DICYANOANILINES CONTAINING 3,4-ETHYLENEDIOXYTHIOPHENE FRAGMENTS: SYNTHESIS AND FURTHER TRANSFORMATION

Some novel 3,5-disubstituted 2,6-dicyanoanilines incorporating 3,4-ethylenedioxythiophene (EDOT) fragment were prepared and investigated. Two different synthetic procedures have been applied for this purpose. One of them consists in the cyclization of chalcones with the malononitrile excess, another one relies on the one-pot three-component strategy. Condensation of thus prepared 3,5-disubstituted 2,6-dicyanoanilines with 3,4-ethylenedioxythiophene-2-carboxaldehyde (EDOT-CHO) has successfully given rise to the corresponding Schiff bases. UV absorption and fluorescence spectra were recorded for the chloroform solutions of the synthesized compounds. The influence of the changes in the compounds’ molecular structure on the UV absorption and fluorescence maxima as well as on the absorption edge position has been analyzed. It has been revealed that the π-conjugation chain elongation results in the red shift of the UV absorption and fluorescence maxima (λmax). The absorption red edge values (λonset) of the Schiff bases’ solutions were found to be crucially shifted to the longwave region if compared with the ones obtained for the solutions of the initial 2,6-dicyanoanilines (142 and 170 nm). The strong bathochromic shifts were also detected for their fluorescence maxima (72 and 114 nm). The optical bandgaps (Egopt) calculated on the basis of the λonset values were found to be less than 2.5 eV for all prepared compounds. Cyclic voltammetry method was used to study the electrochemical behavior of the Schiff bases, as a result the values of the onset oxidation potentials (Eoxonset) were determined and used for calculation of such important characteristics of molecules as the frontier orbital energies (EHOMO и ELUMO). The structures of the synthesized compounds were confirmed by elemental analysis and by IR and 1H NMR spectral data.

Структура, генерационные характеристики и фотостабильность новых гетерил-кумаринов

The effect of the structure of a number of new laser media based on heteryl-coumarins on their spectral and lasing characteristics is studied under conditions of coherent nanosecond and microsecond lamp pumping. The effect of triazole, oxadiazole, and thiazole heterocycles in the structure of coumarin molecules on the spectral, lasing, and photochemical properties of their ethanol solutions has been studied. The analysis of the influence of heteroatoms, heterocyclic radicals, and an aryl fragment in the conjugation chain on the electron density distribution in the structure of coumarin molecules is carried out. It was shown, that triazole and oxadiazole heterocycles provide better lasing ability and photostability of the compounds under study, which made it possible to create new laser media generating radiation in the spectral range 490-560 nm with a sufficiently high efficiency.

Circularly polarized luminescence based chirality transfer of the chiral BINOL moiety via rigid π-conjugation chain backbone structures

Three kinds of chiral BINOL-based polymers could be synthesized by polymerization in a Pd-catalyzed cross-coupling reaction.

Synthesis, optical and electrochemical study of bipolar heterocyclic systems, including 1,2,4-oxadiazole moiety

Two new 3,5-dihetarylsubstituted 1,2,4- oxadiazoles 8 a,b, including N-alkyl substituted carbazole and thiophene moieties, were synthesized as potential components of materials for organic electronics devices. Optical and electrochemical properties of all new compounds were investigated. On the basis of the experimental UV absorption data, the values of bandgap energies equal to 3.44 eV (8a) and 3.05 eV (8b) were determined. The values of their ionization potentials, HOMO levels (−5.62 eV for 8a, −5.46 eV – for 8b), as well as their electron affinity levels, LUMO levels (−2.2 eV for 8a, −2.4 eV – for 8b), were calculated from the results of electrochemical studies. The energy of the triplet excited states of 8 a,b was defined with the help of time-dependent density functional theory (TD-DFT), comprising 2.68 eV (8a) and 2.32 eV (8b), where the greatest value of this parameter was for the compound with a shorter conjugation chain.