The behavior of cucurbit[6]uril at the electrode/solution interface in the presence of magnesium sulfate was investigated and quantified. It has been established that at the highest positive potential available for the adsorption of organic compounds, a structure is formed that consists entirely of neutral cavitand molecules.

An analysis of the impedance data for the Hg-electrode/salt solutions interface of molecular containers of cucurbiturils containing their supramolecular cationic complexes was carried out. The need to study the properties of such systems is determined by their practical use in the field of supramolecular chemistry, medicine, biochemistry, and nanotechnology. The formation of two types of adsorption layers and a significant change in the adsorption behavior with a change in the initial concentrations of the system components and the electrode potential were established. It was shown that the observed changes are due to a change in the concentration of free molecules of cucurbiturils not involved in complex formation. The high sensitivity of the impedance measurement data to this parameter found this way made it possible to establish the corresponding quantitative dependences for systems with known values of the strength constants for complexes of inorganic cations with cucurbiturils. It was shown that for systems close in nature, this opens up the possibility of finding previously unknown strength constants of cationic cucurbiturils complexes when analyzing impedance measurement data. The work showed the applicability of the proposed method for determining the strength constants of supramolecular cationic cucurbiturils complexes, which can be an alternative to more complex and time-consuming methods.

The influence of the electrolyte nature and cation charge on the adsorption properties of cucurbit[6]uril supramolecular complexes are established and discussed. The results show the narrowing of the adsorption potential region of these complexes with increasing cation charge, and the possibility to form an adsorbate layer of supramolecular cations associated with surface-active electrolyte anions at the positive boundary of the adsorption potential region.

An analysis of the array of impedance data for the interface the Hg-electrode/salt solutions of macrocyclic cavitands of the cucurbituril family containing their supramolecular cationic complexes was performed. A significant change in the properties of the adsorption layer was established with a change in the charge of the electrode surface and the concentrations of the components of the complex formation reaction. The existence of two types of adsorption layer was found, one of which (with positive charges on the electrode surface) is formed with the participation of neutral cavitand molecules. The high sensitivity of the impedance data to the presence of these molecules in solution made it possible to establish the corresponding quantitative dependences for systems with known values of the stability constants of cationic complexes. It is shown that these data can be used to find previously unknown stability constants of cationic complexes of a given cavitand formed in other similar salt systems. The applicability of the proposed method was demonstrated using impedance data for systems with known stability constants of cationic complexes (cucurbit[6]uril + Me2 SO4, Me+ = K+, Na+).

Electrochemical properties of cationic complexes of supramolecular cavitands from the cucurbit[n]uril (CBn s ) family are studied. Based on the analysis of a complex of systematic data on these compounds, basic regularities characterizing their adsorption behavior are formulated, in particular, the extremely high surface activity and unusually wide adsorption potential region over which the adsorption layer structure is transformed upon changes of the electrode charge value and sign. The varying of concentrations of reactants involved in the complex-formation reaction (the cavitand and inorganic cation) in the studied systems is shown to change significantly the observed picture of adsorption phenomena. The comparative analysis of adsorption data for systems containing supramolecular complexes of cucurbiturils with different cations can back qualitative estimating of their strength constants. It has been established by example of systems containing inclusive complexes of the СВ7 cavitand with organic cation (the cation of 3,3′-diethylthiocarbocyanine iodide dye) and with organic molecules (super-tough complexes with 1-hydroxyadamantan and ferrocene, the strength constants K of 10 9 –10 10 М –1 by order of magnitude), that including of neutral organic molecule into the cavitand cavity does not prevent the formation of an exclusive complex with sodium cation and that such a complex is not formed in the presence of organic cation in the cavitand cavity. It was demonstrated by example of the cobaltocene(Сос)/cobaltocenium(Сос + ) redox-system studied in the solutions added with СВ7 and СВ7-free ones that the formation of adsorption layer of the Сос + ⊂ СВ7 supramolecular complex particles preceding an electrode process leads to changing of the electrode reaction rate and mechanism.

Effects observed in the catalytic system are explained by a non-covalent interaction of the components of the system with the CNT surface.

Recently in our work it was shown that the catalytic efficiency of organic compound oxidation in the presence of electrochemically generated radical cations of aromatic di-N-oxides was increased several times using single-walled (SWCNT) or multi-walled (MWCNT) carbon nanotube paper electrodes instead of glassy carbon (GC) electrode. It was found that, in the absence of substrate, the oxidation currents of di-N-oxides at SWCNT or MWCNT paper electrodes, in contrast to the GC electrode, exceeded the oxidation current of the ferrocene (Fc) reference several times. In this work, the study of 2,5-di-Me-pyrazine-di-N-oxide (Pyr1) and Fc oxidation in 0.1 M Bu4NClO4 solutions in acetonitrile (MeCN) at GC, SWCNT and MWCNT paper electrodes was performed by methods of cyclic voltammetry, electron paramagnetic resonance (EPR) electrolysis, and differential capacitance. Quantum chemical modeling of adsorption of Pyr1, Fc, and MeСN on CNT surface was carried out using a cluster model describing the surface of conducting and non-conducting carbon nanotubes. The adsorption energies, equilibrium distances for molecular location and orientation on CNT surface were obtained. The observed effects were explained on the basis of quantum chemical modeling of the non-covalent interaction of the components of the studied system with CNT surface.

The aim of this work is to compare the electrochemical behavior of ferricenium and cobalticenium cations and supramolecular complexes formed by these cations and ferrocene with a cavitand - cucurbit[7]uril on glassy carbon and mercury electrodes. On the Hg electrode the adsorption properties of these supramolecular complexes were also studied. The substantial differences in the processes of heterogeneous electron transfer for these systems are explained by the principally different adsorption behavior of supramolecular complexes of these metallocene derivatives on GC and Hg. It was found that the mechanism of reactions of these supramolecular complexes on the Hg electrode is determined by the conditions of formation of their adlayers in the potential region preceding the beginning of electrochemical processes. For complexes formed by ferricenium cation and cobaltocene with cucurbit[7]uril we have determined the more precise values for the constants of complex formation as compared to the literature data (7 x 10(9) M-1 and 1 x 10(8) M-1, respectively).

The complexation of styryl dyes 4-[(E)-2-(3,4-dimethoxyphenyl)]-1-ethylpyridinium perchlorate and trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide with cucurbit[n]urils (CBn) (n = 6, 7) in aqueous solutions in the presence of sodium sulfate with a concentration of 0 to 1 mol/L has been studied by stationary and time-resolved optical spectroscopy, electrochemical, and quantum chemical methods. Adding the electrolyte to the solution decomposes 1 : 1 inclusion complexes with the dyes (D+ · CBn) due to competitive formation of complexes of the cavitand with sodium cations: Na+ · CBn and Na+ · CBn · Na+. Their total formation constants have been determined to be β = 2760 and 168 600 M−2 for CB7 and CB6, respectively, which agrees with the results of quantum chemical calculations. At the same time, no evidence of the presence of Na+ · CBn · D+ type complexes has been found in solutions.

Results of the studies in the adsorption properties of СВ6, СВ7, СВ8 cucurbituril complexes with inorganic cations (Na+, K+, Cs+), cation of 3,3'-diethyltiocarbocyanine iodide organic dye and neutral organic compounds: adamantanol-1 and ferrocene at the electrode/solution interfaces are summarized. Effects of different factors on the adsorption behavior of the studied supramolecular complexes are analyzed.

The aim of this study is to consider the adsorption phenomena at the electrode/solution interface in systems containing complexes of cucurbit[7]uril (CB7) with organic compounds: adamantanol‑1, ferrocene and organic dye 3,3′‑diethylthiocarbocyanine iodide. These guests form exclusively stable inclusive complexes with CB7. Experimental dependences of differential capacitance C as a function of potential were used in calculating the adsorption parameters characterizing the most important properties of adsorption layers formed by compounds under study at the electrode/solution interface. For all the systems studied here, as for those studied earlier, adsorption parameters for negative and positive charges of the electrode surface differ. Obviously this points to deep changes in the properties of adsorption layers depending on the electrode potential.

Studies and quantification of cucurbit[8]uril properties at the electrode/solution interface in a wide range of the electrode potential and adsorbate concentration revealed features of its adsorption behaviour. It forms a mixed adsorption layer similar to cucurbit[7]uril, while cucurbit[6]uril does not.

The results of investigation of the electrochemical properties of cryptand 222 from the macropolycyclic ligands group and its complexes with cations were summarized. Emphasis was placed on the properties of the adsorbed layers of these substances at the electrode/solution interface. Adsorption parameters of the compounds studied were calculated in the framework of the Frumkin–Damaskin theory of adsorption of organic substances using the regression analysis. Comparative analysis of the data obtained was carried out.

The mechanism of oxidation of 2,3,5,6-tetra-Me-pyrazine-di-N-oxide (Pyr(2)) as a mediator of electrooxidation of isopropyl alcohol was studied by cyclic voltammetry at glassy carbon (GC) and single-walled carbon nanotubes (SWCNT) electrodes in 0.1 M LiClO4 solutions in acetonitrile. The adsorption of Pyr(2) at SWCNT electrode in 0.1 M LiClO4 solution in acetonitrile was investigated by measurement of the dependence of the differential double layer capacitance of the electrode C on potential E. The effect of isopropyl alcohol on the shape of cyclic voltammograms (CVs) of Pyr(2) and the intensity of EPR signal of its radical cation was investigated. The catalytic currents were recorded at the oxidation of Pyr(2) at SWCNT and GC electrodes in the presence of isopropyl alcohol. The effect of acid and water (as a base) on the catalytic process was studied. The results were explained in terms of the E1C1E2C2 mechanism of two-stage electrode process characterized by catalytic current recorded at the second electrode stage. The overall two-electron catalytic oxidation of isopropyl alcohol in complex with the Pyr(2) radical cation was assumed to occur. It was found that the use of SWCNT electrode instead of GC one increases the catalytic efficiency of i-PrOH oxidation by 17 times.

For pristine (P-CNWs) and functionalized (F-CNWs) carbon nanowalls (CNWs), the effect of physical adsorption of certain compounds with the skeletal structure of bicyclic molecules (camphor, borneol) and also of macrocyclic compounds (Na+ complexes of cryptand 222 (cryptate) and cucurbit [7]uryl) on the kinetic parameters of redox reactions ([Ru(NH3)6]2+/3+, [Fe(CN)6]3−/4− and Fe2+/3+) has been studied systematically for the first time by the methods of cyclic voltammetry. It is shown, that the adsorption of these compounds on F-CNWs does not change the rate constants k0 of [Ru(NH3)6]2+/3+ and [Fe(CN)6]3−/4− redox reactions, whereas their adsorption on P-CNWs leads to a decrease in k0 by the factor 2.5–10. For the Fe2+/3+ reaction at the presence of organic compounds under study, the effect of inhibition is observed for P-CNWs and for F-CNWs, though to the lesser extent. The diametrically opposite effects of the adsorption of camphor and borneol on the kinetics of this reaction are observed with the transition from the pristine to functionalized electrode surface. It is shown, that the adsorption of two-dimensional condensed layers of camphor and borneol on the atomically smooth mercury surface, induces a decrease in k0 for [Ru(NH3)6]2+/3+ reaction, substantially more pronounced, as compared to P-CNWs (by the factor of 25 and 40, respectively). This difference can be explained by the peculiarities of the topology of carbon nanowalls which determines the preferential occurrence of the redox reactions on the edges of basal planes where the formation of condensed layers by the skeletal and macrocyclic molecules seems to be complicated.