Stereochemistry and chiroptical properties of bimetallic single helicates of hexapyrrole-α, ω-dicarbaldimines with high diastereoselectivity

Bimetallic complexes of hexapyrrole-[Formula: see text],[Formula: see text]-dicarbaldimines consisting of a pair of four-coordinate metal sites adopt a helical closed [Formula: see text]-symmetric form or sigmoidal open forms depending on whether the 2,2[Formula: see text]-bipyrrole subunit at the center of the hexapyrrole chain takes cis- or trans-conformation. X-ray crystallography of a bisNi complex having N-[([Formula: see text]-1-cyclohexylethyl]carbaldimine units at both ends of the hexapyrrole chain revealed a non-symmetric heterohelical open form where the metal coordination sites of opposite helical sense sit on opposite sides of the central 2,2[Formula: see text]-bipyrrole subunit. BisPd complexes preferred a closed [Formula: see text] form and a steric bulk at the 3,3[Formula: see text]-position of the 2,2[Formula: see text]-bipyrrole subunit improved the helical sense bias. A bisPd complex with N-[([Formula: see text]-1-cyclohexylethyl]carbaldimine units adopts a helical closed [Formula: see text] form exclusively with full bias for a [Formula: see text]-helical sense. These bimetallic single stranded helicates were reversibly oxidized to [Formula: see text]-cation radicals at 0.1[Formula: see text]0.3 V vs. a ferrocene/ferrocenium couple and spectroelectrochemistry revealed remarkable absorption and CD spectral changes in the Vis-NIR region.

Comparison of Volatiles and Chemical Composition of Traditional and Non-Traditional Honey Available on the Polish Market

The purpose of the work was to compare the quality of selected honey available on the Polish market, including traditional (rape, lime and meadow and marsh honey) and non-traditional honey (lime, buckwheat, and honeydew honey from coniferous honeydew). Parameters such as electrical conductivity, color, pH, acidity, water, hydroxymethylfurfural, total phenols content, and ability to deactivate ABTS cation radicals were determined. The profile of aroma compounds was carried out by GC-MS technique, and determination of sugars was performed by HPLC. It was found that all tested honey met standards according to European law requirements. Semi-quantitative analysis of volatile compounds showed that all honey samples contain numerous volatiles (in buckwheat honey there were 67 compounds, and in honeydew honey from coniferous honeydew, only 40 compounds). Characteristic volatile compounds of each aroma profile were described e.g., benzaldehyde, acetone, 2-methyl-butanal, nonanal, benzyl alcohol were found in rape honey aroma, and furfural, isovaleric acid, ethanol, delta-valerolactone, isovaleraldehyde, 2-methyl-butanoic acid, and phenylacetaldehyde in buckwheat honey aroma. The total content of volatiles was the highest in buckwheat honey (199.62 µg/kg), and in traditional lime honey (195.17 µg/kg). The lowest total content of volatile substances was established in non-traditional lime honey (73.20 µg/kg) and in rape honey (39.52 µg/kg).

Substituent Effect in the Cation Radicals of Monosubstituted Benzenes

In 30 monosubstituted benzene cation radicals, studied at the ωB97XD/aug-cc-pVTZ level, the phenyl rings usually adopt a compressed form, but a differently compressed form—equivalent to an elongated one—may coexist. The computational and literature ionization potentials are well correlated. The geometrical and magnetic aromaticity, estimated using HOMA and NICS indices, show the systems to be structurally aromatic but magnetically antiaromatic or only weakly aromatic. The partial charge is split between the substituent and ring and varies the most at C(ipso). In the ring, the spin is 70%, concentrated equally at the C(ipso) and C(p) atoms. The sEDA(D) and pEDA(D) descriptors of the substituent effect in cation radicals, respectively, were determined. In cation radicals, the substituent effect on the σ-electron system is like that in the ground state. The effect on the π-electron systems is long-range, and its propagation in the radical quinone-like ring is unlike that in the neutral molecules. The pEDA(D) descriptor correlates well with the partial spin at C(ipso) and C(p) and weakly with the HOMA(D) index. The correlation of the spin at the ring π-electron system and the pEDA(D) descriptor shows that the electron charge supplied to the ring π-electron system and the spin flow oppositely.

Azulenoisoindigo: A Building Block for π-Functional Materials with Reversible Redox Behavior and Proton Responsiveness

<p>Azulene, one of representative nonbenzenoid aromatic hydrocarbons, exhibits unique molecular structure and distinctive physical and chemical properties. Herein, an azulene-based isoindigo analogue, azulenoisoindigo (<b>AzII</b>) is designed and synthesized, which has a twisted molecular backbone and R/S-isomers in single crystals. Interestingly, <b>AzII</b> shows the characteristics of both isoindigo and azulene, such as completely reversible redox behavior and reversible proton responsiveness. UV-vis-NIR, ¹H NMR and electron paramagnetic resonance (EPR) measurements were carried out to get insights into the possible mechanism of the proton-responsive property of <b>AzII</b>. The results demonstrated that only one azulenyl moiety of molecule of <b>AzII</b> was protonated and deprotonated, and the protonated <b>AzII</b> can be further oxidized to form azulenium cation radicals.</p>

Azulenoisoindigo: A Building Block for π-Functional Materials with Reversible Redox Behavior and Proton Responsiveness

<p>Azulene, one of representative nonbenzenoid aromatic hydrocarbons, exhibits unique molecular structure and distinctive physical and chemical properties. Herein, an azulene-based isoindigo analogue, azulenoisoindigo (<b>AzII</b>) is designed and synthesized, which has a twisted molecular backbone and R/S-isomers in single crystals. Interestingly, <b>AzII</b> shows the characteristics of both isoindigo and azulene, such as completely reversible redox behavior and reversible proton responsiveness. UV-vis-NIR, ¹H NMR and electron paramagnetic resonance (EPR) measurements were carried out to get insights into the possible mechanism of the proton-responsive property of <b>AzII</b>. The results demonstrated that only one azulenyl moiety of molecule of <b>AzII</b> was protonated and deprotonated, and the protonated <b>AzII</b> can be further oxidized to form azulenium cation radicals.</p>