FaFrit

Disulfide bridge formation was investigated in helical aromatic oligoamide foldamers. Depending on the position of thiol-bearing side chains, exclusive intramolecular or intermolecular disulfide bridging may occur. The two processes are capable of self-sorting, presumably by dynamic exchange. Quantitative assessment of helix handedness inversion rates showed that bridging stabilizes the folded structures. Intermolecular disulfide bridging serendipitously yielded a well-defined, C₂-symmetrical, two-helix bundle-like macrocyclic structure in which complete control over relative handedness, that is, helix–helix handedness communication, is mediated remotely by the disulfide bridged side chains in the absence of contacts between helices. MM calculations suggest that this phenomenon is specific to a given side chain length and requires disulfide functions

Hand signals: Remote chiral communication of handedness is conveyed between aromatic helical foldamers through disulfide-bridged side chains without any direct contact between helices.

Treatment of meso-chlorosubporphyrin with controlled equivalents of Na₂S·9H₂O in DMF led to the formation of either meso-to-meso sulfide (S)-bridged dimer 4 or disulfide (SS)-bridged subporphyrin dimer 6. S-bridged dimer 4 displayed a split Soret-like band and a large Stokes shift and became a fully delocalized one-quantum system in the S₁ state, as indicated by femtosecond transient absorption anisotropy measurements and theoretical calculations. Contrastingly, SS-bridged dimer 6 showed a broad but nonsplit Soret-like band, no fluorescence, and very fast S₁ decay with a lifetime of 4 ps, which indicated the presence of a rapid decay channel.

meso-to-meso S-bridged and SS-bridged dimers 4 and 6 are prepared by S_NAr reaction of meso-chlorosubporphyrin. Dimer 4 displays a split Soret-like band and a large Stokes shift, whereas dimer 6 shows weaker interchromophoric interaction. Dimer 4 becomes a one-quantum system in the S₁ state, whereas the S₁ state of 6 displays very fast decay to the ground state with a lifetime of 4 ps.

A novel rational synthetic pathway—the “functionalization of para-nitroaniline” (FpNA)—provides substituted hexaarylbenzenes (HABs) with uncommon symmetries that bear up to five different substituents, fully avoiding regioisomeric product distributions during the reactions. 4-Nitroaniline is functionalized by a cascade of electrophilic halogenations, Sandmeyer brominations, and Suzuki cross-coupling reactions, leading to 26 substitution geometries, of which 18 structures are not available by the current established techniques. Furthermore, we demonstrate that this method is applicable to the bulk production of such systems on a multigram scale. Regarding optoelectronic properties, we demonstrate how highly functionalized HABs can show strong luminescent behavior, making these molecules very attractive to organic electronic devices.

Bulk discount on hexaarylbenzenes (HABs): A rational and scalable synthesis of uncommon and highly functionalized HABs utilizes 4-nitroaniline as the starting material. This approach can potentially provide 18 novel HABs and 26 substitution geometries in total, which are not available or only difficult to obtain by standard techniques.

Complex oscillatory behaviors of living cells are demonstrated by R. Yoshida, T. Ueki, and R. Tamate in their Communication on page 5179 ff. by using a biomimetic colloidosome composed of self-oscillating microgels that exhibit autonomous shape oscillations with buckling deformations driven by an oscillatory chemical reaction. The resulting oscillatory waveform profile becomes markedly more complex than that of conventional self-oscillating materials.

A new class of alkaline anion-exchange membranes containing mobile ion shuttles is developed. It is achieved by threading ionic linear guests into poly(crown ether) hosts via host–guest molecular interaction. The thermal- and pH-triggered shuttling of ionic linear guests remarkably increases the solvation-shell fluctuations in inactive hydrated hydroxide ion complexes (OH⁻(H₂O)₄) and accelerates the OH⁻ transport.

The chiral stereoisomers of new non-ionic dendritic amphiphiles self-assemble in aqueous solution towards helical ribbons with opposite handedness. However, in the case of the meso-compound, cylindrical assemblies are observed, as illustrated. Modelling suggests that they consist of right- or left-handed helical molecular strands in equal distribution. The hydrophobic core of such a cylinder is sized to accommodate the hydrophobic tails. Only the head groups and the aromatic platforms, which contribute high density in transmission electron microscopy (TEM), are shown for clarity. The paper discusses stereochemical aspects upon supramolecular assembly of these new dendritic amphiphiles. More information can be found in the Full Paper by C. Böttcher, et al. (DOI: 10.1002/chem.201504504).