Petr Vaňura

A Proton Complex of p-tert-Butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide): NMR Evidence and Probable Structure

Using 1H and 13C NMR together with density functional theoretical (DFT) calculations, it is shown that p-tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) (1) forms a stable equimolecular complex with proton in the form of hydroxonium ion in nitrobenzene-d 5. Protons were offered by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) and converted to hydroxonium ions by traces of water. The complex 1·H3O+ adopts a slightly asymmetric but rapidly motionally averaged conformation, which is distinctly more cone-like than ligand 1. The hydroxonium ion H3O+ is bound partly to thiocarbonyl sulphur atoms and partly to phenoxy oxygen atoms of 1 by strong hydrogen bonds and other electrostatic interactions.

Experimental Evidence for Unusual Protonation of Tetraethyl p-tert-Butylcalix[4]arene Tetraacetate and the Most Probable Structure of the Resulting Complex

Using 1H and 13C NMR, FT IR spectroscopy together with quantum mechanical DFT calculations, we show that tetraethyl p-tert-butylcalix[4]arene tetraacetate (1) forms a stable equimolecular complex with proton in the form of hydroxonium ion in acetonitrile-d 3. Protons for this complex were offered by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) and converted to hydroxonium ions by traces of water. The complex 1·H3O+ adopts a slightly asymmetric conformation, which is distinctly more cone-like than ligand 1. According to spectral evidence, the hydroxonium ion H3O+ is bound mainly to three of the phenoxy oxygen atoms of 1 by strong hydrogen bonds leaving the ester carbonyl groups, which are the usual coordination site for metal cations, free. Theoretical DFT calculations support the bonding to phenoxy oxygen atoms but slightly prefer a structure with one of the carbonyls being involved in the coordination.

Complexation of the thallium cation with dibenzo-30-crown-10: extraction and theoretical study

From extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements, we determined the stability constant of the dibenzo-30-crown-10·Tl+ complex species dissolved in nitrobenzene saturated with water. By using quantum–mechanical calculations, we then predicted the most probable structure of this complex species.Graphical abstract.

Theoretical study on the complexation of bambus[6]uril with the cyanate and thiocyanate anions

Quantum mechanical density functional theory (DFT) calculations were used to derive the most probable structures of the bambus[6]uril·OCN− and bambus[6]uril·SCN− anionic complex species. In these two C3 symmetric complexes, each of the two considered anions, included in the macrocyclic cavity, is bound by 12 weak hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units and the respective anion.Graphical abstract

Complexation of the thallium cation with nonactin: an experimental and theoretical study

From extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements, the stability constant of the nonactin-Tl+ complex species dissolved in nitrobenzene saturated with water was determined. By using quantum–mechanical calculations, the most probable structure of this complex was predicted.Graphical abstract

Contribution to the Complexation of some Univalent Metal Cations with p-Tert-Butylcalix[4]arene-Tetrakis(N,N-Diethylacetamide) in Nitrobenzene Saturated with Water

Abstract From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq)+NaL+(nb)⇔ML+(nb)+Na+(aq) taking place in the two-phase water-nitrobenzene system (M+=Li+, Ag+, Rb+, Tl+, Cs+; L=p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide); aq=aqueous phase, nb=nitrobenzene phase) were determined. Moreover, the stability constants of the ML+ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the cation order Cs+ < Rb+ < Tl+ < Ag+ < Li+.

Individual extraction constants of some dicarbollylcobaltate anions in the water-nitrobenzene system

Individual extraction constants of nine dicarbollylcobaltate anions in the two-phase water-nitrobenzene system were determined radiometrically assuming that the changes of Gibbs energy of the transfer of the tetraphenylarsonium cation, Ph4As+, and of the tetraphenylborate anion, BPh4−, from the aqueous into the nitrobenzene phase are equal. The constants obtained by this method were correlated with Hanschs constants of hydrophobity.

Protonation of Benzo-18-crown-6: Extraction and DFT Study

Abstract From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H3O+(aq) + 1·Na+(nb)⇌1·H3O+(nb) + Na+(aq) taking place in the two-phase water-nitrobenzene system (1 = benzo-18-crown-6, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex(H3O+, 1·Na+)=-0.8±0.1. Further, the stability constant of the 1·H3O+ complex in water-saturated nitrobenzene was calculated for a temperature of 25°C as log βnb(1·H3O+)=6.3±0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the 1·H3O+ cationic complex species was derived. In this complex, the hydroxonium ion H3O+ is bound by three strong linear hydrogen bonds to one (Ar–O–CH2) ethereal oxygen and two (CH2–O–CH2) ethereal oxygen atoms of the parent crown ligand 1. The interaction energy was found to be -401.4kJ/mol, confirming the formation of the considered complex 1·H3O+.

Extraction and DFT study of complexation of the cesium cation with beauvericin

From extraction experiments in the two-phase water–nitrobenzene system and γ-activity measurements, the stability constant of the beauvericin–Cs+ complex species dissolved in nitrobenzene saturated with water was determined. By using quantum–mechanical density functional level of theory (DFT) calculations, the most probable structure of this complex was derived.Graphical abstract

Experimental and theoretical study on the interaction of the pyridinium cation with a hexaarylbenzene-based receptor

Extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements were used to determine the stability constant of a hexaarylbenzene-based receptor/pyridinium complex dissolved in nitrobenzene saturated with water. Further, applying quantum mechanical calculations, the most probable structure of this “asymmetrical” cationic complex was derived.Graphical Abstract