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This review is devoted to the features of isomerization reactions of indoline spiropyrans and the possibilities for their applications as building blocks in the design of molecular machines and ensembles capable of self-organization. Nanoscale systems functioning on the base of changes in geometric parameters and molecular dipole moment when switching between the spirocyclic and merocyanine forms have been considered. The factors that alter the system morphology may be electromagnetic irradiation or the acidity of the medium.

New indoline spiropyran was synthesized by the cyclocondensation of 5-chlorine-substituted Fischer base with 2,7-dihydroxy-1-naphthaldehyde. This spiropyran was used to prepare a new derivative of α-lipoic acid with potential biological activity, which can be considered as a promising photopharmacological agent. The structures of the synthesized compounds were determined by NMR and IR spectroscopy and mass spectrometry and were confirmed by X-ray diffraction. Biological assays using HeLa cells showed that the spirocyclic compounds possess low cytotoxicity even at relatively high concentrations.

Abstract Indoline spiropyran containing an σ-acceptor chlorine atom in 6′ position of the 2H-chromene part of the molecule was synthesized and studied. The use of 1,2,3,3-tetramethyl-3H-indolium perchlorate as a starting compound made it possible to achieve higher product yields as compared to previous studies. The molecular structure of the compound was established by single crystal X-ray diffraction analysis. The features of the crystal structure and intermolecular interactions were investigated using CrystalExplorer17 software package. The photochromic behavior in acetonitrile solution was studied for the first time. It was found that the merocyanine form of spiropyran is characterized by an absorption maximum at 592 nm, which is 37 nm closer to the range of the “biological window” in comparison with the nitro-substituted analog.

This work deals with the study of two derivatives of spiropyrans of indoline series and α-lipoic acid, which are considered as potential photopharmacological agents with controllable biological activity. The structure of the compounds has been studied in detail by X-ray diffraction analysis that revealed high lability of lipoic acid fragments. To assess potential biological activity, molecular docking for the possibility of spiropyran molecule to bind to amylin protein in order to inhibit its aggregation has been performed. The results of molecular docking showed a potential increase in the affinity of spirocyclic derivatives toward this protein as compared with α-lipoic acid.

New spiropyrans with chromene and indoline cores bearing alkoxycarbonyl group and cationic π-acceptor in the chromene moiety were synthesized in one step from 1,2,3,3-tetramethylindolinium and isophthalic dialdehyde derivatives. The appending of a 8′-positioned conjugated cationic fragment causes a significant red-shift of the photoinduced isomers absorption maxima and provides them with extremely long lifetimes up to 75 min. The obtained spiropyrans exhibit both positive and negative photochromism in solutions, demonstrating the properties of ‘photochromic balance’.

The three-dimensional NAM-ECRIS model is applied for studying the metal ion production in the DECRIS-PM Electron Cyclotron Resonance Ion Source. Experimentally measured extracted ion currents are accurately reproduced with the model. Parameters of the injection of metal vapors into the source are optimized. It is found that the axial injection of the highly directional fluxes allows increasing the extracted ion currents of the highly charged calcium ions by factor of 1.5. The reason for the gain in the currents is formation of internal barrier for the ions inside the plasma, which increase the ion extraction and production efficiency. Benefits of injecting the singly-charged calcium ions instead of atoms are discussed.

The review is devoted to mechanically sensitive indoline spiropyrans and their structural features. Recent advances in the study of their isomerization processes are considered, special attention is paid to the effect of pressure on the behavior of spiropyrans in the composition of various photochromic materials and dyes, as well as in the process of the formation of J-aggregates in Langmuir–Blodgett films.

Processes of the secondary electron emission (SEE) from the walls are included into the Numerical Advanced Model of Electron Cyclotron Resonance Ion Sources (NAM-ECRIS). It is found that SEE strongly influences electron confinement time and ion production. With the modified model, we observe reactions of the source to changes in a gas flow into the source and in an injected microwave power. The source performance with scaling the hexapole magnetic field is investigated. The calculated tendencies are close to the experimental observations.

The paper describes the preparation of a new salt spiropyran of indoline series containing vinyl-3H-indolium fragment in the 8' position of the 2H-chromene moiety and a chlorine atom in the benzene ring of the indoline fragment. The structure of the reaction product was studied by IR, 1H, and 13C NMR spectroscopy. The data of X-ray diffraction study indicate that the reaction leads to the partial exchange of the indoline hetarene fragment to provide previously described salt spiropyran containing no chlorine atom in the indoline portion of the molecule.

One-pot synthesis and the structure study of a new salt spiropyran of indoline series containing 2H-chromenic vinyl-3H-indolium fragment as a substituent at the position 8 are described. The structure was confirmed by the method of NMR 1H and 13C spectroscopy, IR and high-resolution mass spectrometry. The single crystals of the compound were investigated by X-ray analysis. The structure was compared with the previously known isostructural analogue [10].

A one-pot synthesis and structure study of a new salt spiropyran of the indoline series containing 2H-chromene vinyl-3H-indolium moiety as a substituent at the 8'-position are described. The structure was confirmed by 1H and 13C NMR and IR spectroscopy and high-resolution mass spectrometry. The single crystals of the compound were investigated by X-ray diffraction analysis. The structure was compared with the previously known isostructural analog.

The synthesis and study of the structure and photochromic properties of the new salt spiropyrans of the indoline series containing chlorine and bromine atoms as a substituent at the 6' position in 2H-chromene moiety are presented. The structure of the obtained compounds was confirmed by NMR 1H spectroscopy and X-ray diffraction analysis. The compounds are photochromic; the long-wavelength maximum of the absorption band of their open photoinduced form has a significant hypsochromic shift, and the lifetime substantially increases in comparison with the fluorine analog.

New indoline spiropyrans containing conjugated cationic fragments and bulky substituents in the 2H-chromene moiety were synthesized by a simple one-pot method. The structures of the obtained compounds were confirmed by 1H and 13C NMR (including 2D methods) and IR spectroscopy, as well as by element analysis and HRMS. Molecular structure of 1,3,3-trimethyl-6′-formyl-8′-benzyl-spiro[indoline-2,2′-2H-chromene] was refined by single crystal X-ray. A comparative analysis of the spectral and photochromic properties of salt spiropyrans and similar structures without a cationic fragment was carried out. It was found that the introduction of the cationic substituent at the 6′-position of the 2H-chromene moiety leads to a significant increase in the photoinduced isomer's lifetime.

Synthesis, structure study, and photochromic properties of new salt spiropyrans of indoline series containing chlorine and bromine atoms in the 6'-position of the 2H-chromene moiety have been reported. The structure of the obtained compounds has been confirmed by 1H NMR spectroscopy and X-ray diffraction analysis. The compounds are photochromic; the long-wavelength absorption maximum for photoinduced isomer shows a considerable hypsochromic shift, while the lifetime increases considerably as compared with the fluorine-containing analog.

The three-dimensional particle-in-cell model NAM-ECRIS is used for investigation of how the DECRIS-PM Electron Cyclotron Resonance Ion Source is reacting to changes in the source magnetic configuration. The accent is made on changes in the magnetic field at the magnetic trap center, the minimum-B value. It is calculated that the optimal normalized value of the field is ∼0.8, close to the experimental observations. The reasons for existence of the optimum are discussed. It is observed that the electron energies are increasing with the increased minimum-B values due to enhanced confinement of the energetic electrons in the plasma. Bumps in energy spectra of the radially lost electrons are observed and explained to be due to nonadiabatic losses of electrons.

A new salt spiropyran of indoline series containing benzyl substituent in the 8'-position of the [2H]-chromene moiety of the molecule has been synthesized and studied. The structure of the obtained compound has been confirmed by methods 1H NMR and IR spectroscopy. The study of spectral characteristics and photochromic behavior of the target compound has shown that growing of its single crystal resulted in destruction on account of hydrolysis in acetonitrile. The 1H NMR spectra of the initial salt spiropyran and product of hydrolysis have been compared.

The structure and photochromic transformations of composite organometallic nanosystems composed of Ag nanoparticles covered with a layer of indoline-spiropyran (ISP) molecules from solutions were studied by spectrophotometry, surface Raman scattering spectroscopy (SERS) and quantum chemistry. Analysis of experimental data showed that studied nanostructured systems have photochromic properties, manifested in the reversible photo-induced changes both of the electronic-absorption spectra and of the relative intensity of the SERS bands. The open form of ISP, formed in the organometallic nanostructured film as a result of photochromic transformations, has an adsorption geometry, and, possibly, a conformation different from that formed as a result of chemisorption of ISP molecules on silver colloids.

Synthesis, study of structure and photochromic properties of new salt spiropyran of indoline series containing a fluorine substituent in the 6′-position of the 2H-chromene moiety have been described in the work. The structure of the compound has been confirmed by 1H NMR spectroscopy and X-ray diffraction analysis. Comparison of the structure of the compound with the previously studied analogue containing a methyl group instead of a fluorine atom in the 6′-position of the [2H]-chromene moiety has been made. This compound has been found to be photochromic, long-wavelength absorption maximum of its open form shows a bathochromic shift, and lifetime is increased three times as compared with the methyl analogue.

New spiropyran salts in the row of 1,3,3-trimethylspiro-indoline-2,2'-[2Н]-chromene are prepared and their structures are investigated. Molecular structures of obtained compounds are confirmed by X-ray diffraction and NMR spectroscopy. An open merocyanine isomer is found to be the most stable structure for one of these compounds.

Most often, reagent methods are used to treat wastewater from Cr (VI) compounds. This treatment technology allows reducing the concentration of Cr (VI) in wastewater only. Comparing the composition of wastewater after reagent treatment of chromium compounds using Ca(OH)2 with established standards, it can be concluded that it is necessary to purify a number of pollutants. In this study, wastewater afterpurification of chromium compounds production by the ultrafiltration and reverse osmosis was considered. Modelling processes using WAVE 1.72 software confirmed that the proposed post-treatment scheme was highly efficient and that wastewater could be discharged into a water body without harming it. © Published under licence by IOP Publishing Ltd.

Results of a new series of observations of the anomalous pulsar B0943+10 carried out on the Large Scanning Antenna and DKR-1000 radio telescope of the Pushchino Radio Astronomy Observatory at 112 and 62 MHz, respectively, are presented. Several hundred pulse-arrival times (PATs) obtained on various days in 2013–2016 that correspond to the burst (B) mode emission are analyzed. A method for establishing the many-hour pulse shift in the emission window from 3.5-minute fragments is proposed. The delay of the mean pulse relative to the pre-calculated value follows an exponential law with a relaxation time of about 47 minutes. The pulse delay grows by 6 ms during the five hours following the onset of a burst. The random scatter of the residual PAT deviations is comparable to the amplitude of the systematic variations in these times over the lifetime of the B mode. These observations show that the character of the pulse delay as a function of time is the same at 112 and 62 MHz.

Photochromic molecules which can absorb and emit light within the “biological window” (650–1450 nm) are of great interest for using in various important biomedical applications such as bio-imaging, photopharmacology, targeted drug delivery, etc. Here we present three new indoline spiropyrans containing conjugated cationic fragments and halogen substituents in the 2H-chromene moiety which were synthesized by a simple one-pot method. The molecular structure of the obtained compounds was confirmed by FT-IR, 1H and 13C NMR spectroscopy (including 2D methods), HRMS, elemental and single crystal X-ray analysis. Photochemical studies revealed the photochromic activity of spiropyrans at room temperature which caused photoswitchable fluorescence in the near-IR region after UV-irradiation. While the spirocyclic forms of compounds demonstrated absorption bands in the UV–Vis spectra with maxima in the visible region at about 445 nm and were not fluorescent, the photogenerated merocyanine isomers absorbed in the near-IR range at 708–738 nm and emitted at 768–791 nm. It was found that compound 1a with fluorine substituent possesses the most red-shifted absorption and emission bands of merocyanine form among all the known photochromic spiropyrans with maxima at 738 and 791 nm correspondingly. TD DFT calculations have shown that the longest wavelength absorption maxima of the merocyanine forms correspond to S0-S1 transitions of the isomers with at least one trans-trans-trans-configured vinylindolium fragment which brings them closer to cyanine-like structure and causes an appearance of the absorption and emission bands in the near-IR region.

Indoline spiropyrans containing conjugated cationic vinyl-3H-indolium fragment and their analogues with formyl substituent in the 2H-chromene moiety were synthesized by a simple one-pot method. The structure of the obtained compounds was confirmed by 1H and 13C NMR (including 2D methods) and IR spectroscopy, as well as by element analysis and HRMS. Molecular structures of 1,3,3,6´-tetramethyl-8´-formyl-spiro[indoline-2,2´-2H-chromene] 8 and its cationic derivative 5 were refined by single crystal X-ray and compared. Notably, it was found that the crystals of formyl-substituted spiropyran contain both enantiomers (R- and S-) of the molecule in the unit cell. Photochromic properties of all the compounds were studied and compared using spectral-photokinetic methods. It was found out that electron-withdrawing substituents (vinyl-3H-indolium fragment and formyl group) located at the position 6´ of 2H-chromene moiety stabilize merocyanine isomer more effectively, than at the position 8´, leading even to the appearance of negative photochromism for the compound 3 with cationic substituent, which is quite unusual for this class of organic photochromes. Also, it was shown that chlorine atoms as σ-acceptors at the positions 5 and 5´´ of hetarene moiety and cationic fragment can suppress photochromic behavior.

Four novel bis-spiropyrans possessing two different photochromic units based on indoline and 1,3-benzoxazine heterocycles which are connected through the common 2H,8H-pyrano[2,3-f]chromene moiety and modified with electron donating substituents were obtained by multistep synthesis starting with 2,4-dihydroxy-iso-phthalic aldehyde. The structure of the compounds was confirmed by 1H and 13CNMR, FTIR and HRMS. All bis-spirocompounds exhibited photochromic activity at room temperature. Investigation of photochromic properties of bis-spiropyrans revealed that their once-opened merocyanine isomers were more stable than the double-opened ones under experimental conditions. It was also found that modification of the benzoxazine moiety of the molecule with electron donating substituents along with introduction of bulky benzyl group close to the oxazinespiro-center leads to an increase of the merocyanine lifetime up to 148 s.

Three-dimensional numerical model is developed and applied for studies of physical processes in Electron Cyclotron Resonance Ion Source. The model includes separate modules that simulate the electron and ion dynamics in the source plasma in an iterative way. The electron heating by microwaves is simulated by using results of modelling the microwave propagation in the plasma by the COMSOL Multiphysics® software. Extracted ion currents and other parameters of the source are obtained for different gas flows into the source. It is observed that the currents are strongly influenced by ion transport in transversal direction induced by the plasma potential gradients. Impact of some special techniques on the source performance is investigated. Magnetic field scaling is shown to reduce the ion losses during their movement toward the extraction aperture, as well as use of the aluminum chamber walls and mixing of the working gas with helium.