E. V. Lukovskaya

Supramolecular control of photochemical and electrochemical properties of two oligothiophene derivatives at the air/water interface.

Two geometric isomers of oligothiophene derivatives containing two crowned styryl fragments in 2- or 3-positions of thiophene rings are able to form stable monolayers on the water subphase. The organizing of crown-containing oligothiophenes in monolayers is guided by the π-stacking interaction of hydrophobic styrylthiophene fragments and interaction of hydrophilic macrocycles with the water subphase. The difference in structure of oligothiophene molecules leads to the formation of distinct monolayer architectures with various electrochemical and optical characteristics.

Control of photochemical properties of monolayers and Langmuir-Blodgett films of amphiphilic chromoionophores

Control of the structure of ultrathin films that determine the steric conditions of the passing of intermolecular interactions is one of the most promising methods of implementing the advantages of planar supramolecular systems as basic elements of nanosize information devices. This work studies the behavior of Langmuir monolayers of a new amphiphilic crown-substituted chromoionophore I on a water subphase. It is found that dithiaazacrown ether in molecule I selectively binds Hg2+ cations both in organic solvents and from aqueous subphase. The electronic absorption spectra of the monolayer showed that H-aggregation occurs actively in the course of two-dimensional compression on deionized water, which hinders the complexation process, while the presence of Na+ and Ba2+ cations in the subphase results in the effective inhibition of this aggregation. This conclusion is confirmed by spectral fluorimetric studies of monolayers of a dye with a similar structure that contains a chromophoric group with a much higher fluorescence quantum yield. Monolayer aggregation on deionized water at the surface pressure values of just 4–6 mN/m leads to the three- to fourfold fluorescence quenching, while in the case of subphases containing inert (noncomplementary to the dye ionophoric fragment) cations, the compression of the monolayer to pressures of 25–30 mN/m reduces the fluorescence intensity by no more than 25–35%. It was thus found that variations in the subphase composition allows one to monitor the degree of aggregation of the monolayer and the efficiency of cation recognition.

Metal ion modulated torsion angle in a ditopic oligothiophene ligand: toward supramolecular control of π conjugation.

A π-conjugated oligomer bearing two 15-crown-5-containing styryl moieties connected at the inner β positions of the terminal thiophene nuclei can adopt either a U or a Z shape depending on the structures of its complexes with magnesium and barium ions. We show that barium cations lead to the formation of a mononuclear complex in solution, which causes the system to fold into the U shape. Magnesium ions lead to the same effect at low concentration, but force the ligand to adopt the Z-shaped geometry at high concentrations favoring formation of a binuclear complex. These geometrical reorganizations in solution are accompanied by profound changes in spectroscopic properties, which can be rationalized in terms of variations in the extent of electron delocalization along the oligothiophene backbone. The effects are analyzed by mass spectrometry and (1)H NMR, UV/Vis absorption, and fluorescence spectroscopy in the steady-state and time-resolved regimes. The experimental results are compared to data calculated by using MOPAC2007 with the PM6 Hamiltonian including the COSMO solvation model.

Synthesis of chromophoric crown-containing styryl derivative of terthiophene and its complexation with octane-1,8-diaminium diperchlorate

Abstract2,2′: 5′,2″-Terthiophene derivative containing benzo-18-crown-6 fragments linked through ethene spacers was synthesized, and its complexation with octane-1,8-diaminium diperchlorate in acetonitrile was studied by spectrophotometric titration, 1H NMR, and mass spectrometry. The 1: 1 stoichiometry of the complex was confirmed by mass spectrometry, and its structure was proposed on the basis of the 1H NMR data.

Synthesis, complex-formation, and extracting ability of new derivatives of dithia-13(16)-crown-4(5) ethers

Various methods of synthesizing functional derivatives of dithia-13(16)-crown-4(5) ethers are proposed. Complex-formation of the obtained compounds with Ag+ and Pb2+ ions has been studied using 1H NMR. A radiometric method was used to investigate the extracting ability of substituted dithia-13(16)-crown-4(5) ethers in relation to Ag+ and Cd2+ ions from aqueous solution in the presence of anions of various degree of hardness, with determination of the metal content.

Synthesis and extraction properties of oxathiacrown compounds containing benzyl groups

Abstract8-Benzyl-1.4-dioxa-7,10-dithiacyclododecane and 11-benzyl-1,4,7-trioxa-10,13-dithiacyclopentadecane were obtained by the interaction of (2,3-dibromo-1-propyl)benzene with 1,8-dimercapto-3,6-dioxaoctane and 1,11-dimercapto-3,6,9-trioxaundecane. The extracting ability of the obtained compounds has been studied in relation to Sr2+ and Pb2+ ions from aqueous solutions in the presence of anions of various degrees of hardness with determination of the metal content by a radiometric method.

Effect of light irradiation on the gas sensor characteristics of the SnO2 and ZnO modified by tetrathiafulvalene derivative

Abstract We present the description of the synthesis and characteristics of the SnO2 and ZnO modified by novel tetrathiafulvalene (TTF) derivative. The analysis of the gas sensor properties showed the possibility of light photoactivation of modified semiconductor gas sensor due to the electron transfer from LUMO of TTF molecule to the conduction band of semiconductor matrix.

New functionalized dithia-12(13)-crown-4 ethers: Synthesis, complex formation, and extraction capacity

Abstract1,4-Dioxa-7,10-dithiacyclododecane-8-carbonitrile, 1,4-dioxa-7,11-dithiacyclotridecan-9-one, its 2,4-dinitrophenylhydrazone, and unsubstituted 7,10-dithia-12-crown-4 were synthesized. The complexing ability of the four synthesized dioxadithiacrown compounds toward Ag(I), Pb(II), Hg(II), and Cd(II) ions was assessed by 1H NMR. The extracting ability of the three dioxadithiacrown compounds with respect to the Sn(II) ion from aqueous solutions was studied. The thermal stability of 1,4-dioxa-7,10-dithia-cyclododecane and the corresponding 8-carbonitrile was investigated.

Planar supramolecular systems based on geometrical isomers of crown-containing oligothiophenes

The properties of ultrathin films of two geometric isomers of oligothiophene derivatives containing two crowned styryl fragments in 2- (I) or 3- (II) positions of thiophene rings (Fig. 1) are studied in this work. The ability of these compounds to form stable monolayers at the air/water interface is shown. The structural organization of crown-substituted oligothiophenes in monolayers is determined by the π-π-stacking interaction of hydrophobic styrylthiophene fragments and interaction of hydrophilic macrocycles with the water subphase. Analysis of ultrathin film physicochemical characteristics has shown that the difference in the structure of oligothiophene molecules leads to the formation of distinct monolayer architectures with various electrochemical and optical characteristics. Two types of aggregates (H and J) are generated in monolayers formed from different geometrical isomers at the air/water interface. The effect of barium cation presence in the subphase on the oligomer aggregation in monolayer is discussed. The phase diagrams characterizing the behavior from two-dimensional mixtures of studied crown-substituted oligothiophenes and amphiphilic spreader are plotted basing on compression isotherms accompanied by absorbance and fluorescence spectra of monolayers of different composition. The ability to fine tune the emitted radiation parameters is demonstrated. The obtained results show the efficiency of application of geometrical isomers for investigation of the fundamental “structure-property” ratio of planar supramolecular systems, which is important for organic optics and electronics.

Pseudorotaxane Structures Based on Thiophene-Containing Dibenzo-24-crown-8 Ether Derivatives

Разработан метод получения дибензо-24-краун-8-эфиров (ДБ24К8), содержащих один или два 3,4-диоксиэтилентиофеновых заместителя, с помощью реакции кросс-сочетания по Стилле. Исследование комплексообразования монозамещенного ДБ24К8 с виологеном с использованием спектральных и электрохимических методов подтвердило образование псевдоротаксановой структуры. Строение синтезированных соединений доказано с помощью комплекса физико-химических методов.