Reactivity in organised assemblies

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

“…This may be accounted for on the basis of kinetic cmc, i.e., deviation in cmc of the surfactant from aqueous medium to the reaction medium. To support this conclusion, cmc of the investigated surfactants was also determined conductometrically in a buffer medium of pH 8.0 in the presence of nucleophile, [2-PAM] = 1 × 10 −3 M. As depicted in Table V, a reduction in cmc values was observed for all the cationic surfactants and thus the formation of micelles or premicellar aggregates in the reaction medium can be assumed [33]. Also, it has been documented that with a rise in pH, cmc of surfactants generally decreases [34,35].…”

“…The effect would correspond to a general decrease in the polarity of the head group region that would therefore increase the rate of the nucleophilic substitution 16,41. Another possible explanation is the steric effects by the phenyl rings in the head group region that would activate the bound substrate toward substitution 33. The rate enhancement for the hydrolytic reactions in cationic micelles may also be explained on the basis of reduction in the acid dissociation constants (p K a ) of monopyridinium oximes due to the micellar environment.…”

Creating and mastering nano-objects to design advanced catalytic materials

“…One possibility is to use organized assemblies, including supramolecular aggregates, colloidal structures (e.g., micelles, microemulsions), liquid crystals, dendrimers, and mono-and multi-layers. The effects on the reactivity may be classified in four areas [82]:…”

Reactivity in organised assemblies

“…Typically the observed reactivity at the interface between an organised assembly and the bulk phase depends on the surface pH. 3 Smirnov, Chechik and co-workers 54 presented a molecular probe technique for assessing the pK a at the interface with water of tiopronin-protected gold nanoparticles. They used a series of spin-labeled ligands containing a disulfide moiety for anchoring to the Au surface and a nitroxide whose EPR spectral parameters are sensitive to the pH of the medium.…”

“…We have chosen to interpret ''organised assemblies'' in a rather more liberal way than in previous years. [1][2][3] now including assemblies such as those involving DNA as well as constructions resulting from dynamic combinatorial self assembly which were turned into covalent ''non dynamic assemblies''. In all cases, however, (self) organisation and (self) assembly are crucial to the results discussed.…”