No abstract

Stir it up! Comparison of the evolution with time of J‐aggregates of the title porphyrin in stagnant and vortex‐stirred solutions showed that chiral‐sign selection is due to the action of hydrodynamic gradients (shear flows) on particle folding. Brownian dynamics (stagnant solution) result in irregularly folded mesophases, whereas hydrodynamic gradients (vortex stirring) lead to long‐order folding and formation of helical ribbons (see picture).

The structure of the meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS 4 ) J-aggregates could be determined by X-ray and electron diffraction methods. A sheet-like architecture reveals the relationship between structure and chirality, optics and shapes of the J-aggregate of the meso 4-sulfonatophenyl-and phenyl-10 substituted porphyrins. The structure of the J-aggregates of H 4 TPPS 4 belongs to the chiral space group P2 1 and includes four porphyrin molecules in its unit cell. The intermolecular stabilization of the zwitterionic units by hydrogen bonding and electrostatic interactions between the positively charged central NH groups and the periphery anionic sulfonato groups results in a structure of porphyrins sheets along the [

There are few unambiguous reports describing the transfer of chirality from stirring vortices down to the level of electronic transitions. In this tutorial review the methods reported are discussed as well as the structural trends that seem to be necessary conditions in order to detect this phenomenon.

A widely studied achiral porphyrin, which is highly soluble in aqueous solutions (TPPS4), is shown to self‐assemble into helical nanotubes. These were imaged by electron cryo‐microscopy and a state‐of‐the‐art image analysis allows building a map at ∼5 Å resolution, one of the highest obtained so far for molecular materials. The authors were able to trace the apparent symmetry breaking to existing nuclei in the “as received samples”, while carefully purified samples show that both handnesses occur in equal amounts.