Cascade and Commutative Self-Assembles of Nanoscale Three-Component Systems Controlled by the Conformation of Thiacalix[4]arene

In this work, the formation of two- and three-component supramolecular systems based on cone, partial cone, 1,3-alternate stereoisomers of heteroditopic “hosts”: <i>p-tert-</i>butylthiacalix[4]arene containing 4-amidopyridine fragments with silver(I) cations and dicarboxylic acids in liquid and solid phases were studied by UV spectroscopy, dynamic light scattering, and atomic force microscopy methods. It has been shown that these macrocycles are coreceptors, capable of simultaneously binding silver(I) cations, dicarboxylic acids (oxalic, malonic, succinic, maleic, fumaric acids), and hydroxyl acids (glycol, tartaric acids). For the first time, by the dynamic light scattering method, it has been shown that the conformation of p-<i>tert</i>-butyl thiacalix[4]arenes significantly affects the type of three-component system formed: cone is characterized by the formation of cascade systems; for partial cone, intermediate systems; and for the 1,3-alternate stereoisomers, three types of three-component systems (cascade, intermediate, and commutative) were observed

Micellization and Catalytic Properties of Cationic Surfactants with Head Groups Functionalized with a Hydroxyalkyl Fragment

The catalytic activity of two homological series of cationic surfactants bearing a hydroxyalkyl fragment in the head groups R­(CH₃)₂N⁺(CH₂CH₂OH)­Br^– and R­(CH₃)₂N⁺(CH₂CH₂CH₂OH)­Br^– toward the cleavage of the <i>p</i>-nitrophenyl esters of carbonic acids of different hydrophobicity (acetate, caprilate, caprinate, laurate, myristate) is shown to exceed that of typical cationic surfactants with the trimethylammonium (TMA) headgroup. The catalytic effect increases with the alkyl chain length of surfactants and nonmonotonous changes in the series: acetate < caprilate < myristate < laurate < caprinate, reaching 750 times. NMR and IR spectroscopy studies and the surface potential calculations revealed that the higher catalytic effect of hydroxyalkylated surfactants is not due to their higher surface potential and binding capacity toward substrates. This is in line with finding that binding constants for TMA series are higher than for their hydroxyalkylated analogues, which was demonstrated by the fitting of kinetic data in terms of the pseudophase model. The microenvironment factor rather than concentrating effect is responsible for the advanced catalytic properties of hydroxyalkylated surfactants in the micellar phase

Langmuir Monolayers and Thin Films of Amphifilic Thiacalix[4]arenes. Properties and Matrix for the Immobilization of Cytochrome <i>c</i>

Formation and properties of Langmuir films of thiacalix[4]­arene (TCA) derivatives containing N-donor groups on the lower rim (YO­(CH₂)₃CN; OCH₂CN; NH₂; OCH₂ArCN-<i>p</i>) in <i>1</i>,<i>3</i>-<i>alternate</i> conformation on aqueous subphase and solid substrates have been studied. Only <i>tetra</i>-cyanopropoxy-<i>p</i>-<i>tert</i>-butylthiacalix­[4]­arene <b>1</b> forms a typical monomolecular layer with perpendicular orientation of the macrocycle relative to the water–air interface that is able to immobilize cytochrome <i>c</i> in the entire range of the surface pressure. Obtained monolayers were transferred by Langmuir–Schaefer technique onto quartz, indium–tin oxide (ITO), and silicon. It was demonstrated that protein activity is retained after immobilization on the substrate

Polyelectrolyte Capsules with Tunable Shell Behavior Fabricated by the Simple Layer-by-Layer Technique for the Control of the Release and Reactivity of Small Guests

A novel simple protocol for the layer-by-layer coating of uncharged organic substrates (hydrophobic carboxylic acid esters, CAEs) and control of their loading/release behavior has been developed. The approach involves the preliminary treatment of CAEs with the cationic surfactant cetyltrimethylammonium bromide followed by poly­(acrylic acid)/polyethyleneimine alternate deposition. The basic hydrolysis of the substrates is used to spectrophotometrically control the loading/release behavior through monitoring the absorbency of the reaction product <i>p</i>-nitrophenolate ion. Unlike the reactivity of free CAEs, highly sensitive to the solution pH, and the presence of micellar catalysts, the reaction rate of the loaded substrates is unaffected by reaction conditions and can be administered by the capsule design (numbers of deposition cycles, adjusted pH, ultrasonication). The developed protocol makes it possible to omit the use of the sacrificial template and stages of its removal. Capsules corresponding to the biorelevant size criterion, with diameter of ≤200 nm, are obtained. They can be successfully applied for sustaining the dosage of different specimens with the desirable rate and for the control of the guest reactivity by tuning the shell permeability

Tb(III)-Doped Silica Nanoparticles for Sensing: Effect of Interfacial Interactions on Substrate-Induced Luminescent Response

The present work introduces the easy modification of the water-in-oil microemulsion procedure aimed at the doping of the Tb­(III) complexes within core or shell zones of the silica nanoparticles (SNs), which are designated as “core-shell”, “shell”, and “core”. The dye molecules, chelating ligands, and copper ions were applied as the quenchers of Tb­(III)-centered luminescence through dynamic or/and static mechanisms. The binding of the quenchers at the silica/water interface results in the quenching of the Tb­(III) complexes within SNs, which, in turn, is greatly dependent on the synthetic procedure. The luminescence of “core” SNs remains unchanged under the binding of the quenchers at the silica/water interface. The quenching through dynamic mechanism is more significant for “core–shell” and “shell” than for “core” SNs. Thus, both “core–shell” and “shell” SNs have enough percentage of the Tb­(III) complexes located close to the interface for efficient quenching through the energy transfer. The quenching through the ion or ligand exchange is most efficient for “core–shell” SNs due to the greatest percentage of the Tb­(III) complexes at the silica/water interface, which correlates with the used synthetic procedure. The highlighted regularities introduce the applicability of “core–shell” SNs used as silica beads for phosphatidylcholine bilayers in sensing their permeability toward the quenching ions

A Supramolecular Amphiphile Based on Calix[4]resorcinarene and Cationic Surfactant for Controlled Self-Assembly

A novel supramolecular system based on calix[4]­resorcinarene sulfonatoalkylated at the lower rim and piperidine-methylated at the upper rim and the cationic surfactant hexadecyl-1-azonia-4-azobicyclo[2.2.2]­octane bromide was investigated by methods of NMR, tensiometry, conductometry, potentiometry, dynamic light scattering, X-ray powder diffraction, and spectral probe techniques. Both types of molecules were found to self-associate in aqueous solution, with aggregates of different morphology formed. Importantly, a supramolecular amphiphilic binary system with controlled structure and binding behavior could be fabricated. At high surfactant concentration, the formation of its own aggregates takes place. In the systems with the excess of cyclophane the supramolecular amphiphiles are formed, which, in turn, self-assemble in particles with a large hydrophobic core. Thereby the structure of supramolecular species is determined by relative fractions of components and, hence, could be selectively controlled. The found properties can be used for the design of nanocontainers with the controlled cavity size