This study focuses on the synthesis of a new spiropyran with an azomethine moiety. The synthesis was carried out by a condensation reaction between formyl-substituted spiropyran and para-anisidine. A detailed study using NMR, FT-IR, and mass spectroscopy was carried out to confirm the structure of the resulting azomethine. Particular attention was paid to single crystal X-ray diffraction analysis. Hirshfeld surface calculations were performed to elucidate the nature and relative contributions of the intermolecular interactions that govern crystal packing. Since the molecule has two fragments prone to photoisomerization, one of the main objectives of the study was to study its behavior under UV irradiation. Establishing the relationship between the structure and properties of such compounds is an important and actual task for the molecular design of organic photochromes. During spectral-kinetic studies the target compound showed unexpected photochromic behavior different from standard formation of a merocyanine isomer. With support of quantum chemical calculations, the predominant photoactivation path through azometine fragment cis-trans isomerization was established. Due to the fact that the molecule contains several structural fragments that determine its potential activity against bacteria and biofilms, as well as the inhibition of β-secretase, we have given a preliminary assessment of the prospects for using the resulting azomethine for pharmaceutical purposes using the molecular docking method.

Novel azine-fused [6]helicenes were prepared in five synthetic steps starting from commercially available 2,3-dihaloazines (2,3-dibromopyridine, 2,3-dichloropyrazine and 2,3-dichloroquinoxaline). The X-ray structures, UV-vis absorption and fluorescence spectra of the helicenes were investigated and compared to those of the parent [6]carbohelicene. It was shown that pyrazine-fused [6]helicenes, bearing a pyren-1-yl or 1,8-bis(dimethylamino)naphthalen-4-yl side substituent, contain both helical and axial stereogenic elements and exist as a mixture of stable (P,Sa)-, (M,Ra)-, (P,Ra)- and (M,Sa)-isomers at room temperature. The barriers to R/S- and P/M-isomerizations, as well as the relative stabilities of the isomers, were estimated theoretically.

The exploitation of molecular self-assembly, which leads to the formation of aggregates, represents one of the most crucial approaches in the fabrication of advanced functional materials. A fundamental aspect in this area is the development of novel strategies to construct supramolecular architectures with new (unusual) properties, in particular, strongly fluorescent H-aggregates. Using 2-(2-carboalkoxy-3,4,5-trichloro-6-hydroxyphenyl)benzoxazoles (HBOs) as building blocks, H-aggregates were successfully obtained in both aqueous binary mixtures and the crystalline state. These aggregates exhibit intense fluorescence despite the prohibition imposed by Kasha's rule. This violation seems to result from the deactivation mechanism of the excited excitonic state in HBO H-aggregates, which involves, along with internal conversion, a photochemical channel induced by excited-state intramolecular proton transfer (ESIPT) rather than a radiative one. The consequence of ESIPT is monomeric fluorescence from the keto forms of HBOs. The fluorescence quantum yields of HBOs in the crystalline state are significantly higher than those in solution, ranging from 0.81 to 0.91. This enhancement is due to intramolecular hydrogen bonds as well as the dense molecular packing of HBOs, which suppresses conformational transformations.

New F16 derivatives – (E)-4-(1H-indol-3-ylvinyl)-N-alkylpyridinium salts containing phenyl substituents on the pyridine ring were prepared by the reaction of (E)-4-(1-(1-methyl-1H-indol-3-yl)prop-1-en-2-yl)-2,6-diphenylpyrylium perchlorate with amines. The use of pyrylium salts as starting compounds is an advantage over traditional F16 syntheses, based on the reactions of pre-synthesized pyridines, since it allows the introduction of any aromatic and/or aliphatic substituents into the pyridine ring. The obtained compounds exhibit properties of dual-state emission (DSE). The extremely low fluorescence quantum yields in solution (ϕf ≤ 0.004) significantly limit their practical applications. However, the substantially higher quantum yields observed in the solid state (ϕf = 0.023–0.045) suggest their potential utility for imaging in aggregated or membrane-bound systems. Photoinitiated processes in F16 derivatives, along with the fluorescence of the original E-isomeric forms, include photochromism, which allows them to be considered as fluorescent molecular switches. The optical properties of one of the compounds allow it to be used to assess membrane potential in isolated mitochondria and observe its accumulation in mitochondria of living cells by fluorescent microscopy. A comparison of the penetration of the lipophilic cations, both those obtained in this study and known in the literature, through an artificial lipid bilayer membrane in response to the application of a transmembrane electrical potential is carried out.

6-Bromo- and 6,7-dibromo-1,3-dimethyl-1H-perimidin-2(3H)-ones were arylated with arylboronic acids under Suzuki-Miyaura reaction conditions to afford 6-aryl-, 6-bromo-7-aryl- and 6,7-diaryl-1,3-dimethyl-1H-perimidin-2(3H)-ones. A comparison of the X-ray structural parameters of peri-diaryl derivatives of 1,3-dimethyl-1H-perimidin-2(3H)-one, naphthalene and 1,8-bis(dimethylamino)naphthalene (proton sponge) was performed. Based on the data of dynamic 1H NMR spectroscopy and quantum-chemical calculations, barriers to syn/anti-isomerization of 6,7-diaryl-1,3-dimethyl-1H-perimidin-2(3H)-ones were estimated. The optical properties of 6-aryl- and 6,7-diaryl-1,3-dimethyl-1H-perimidin-2(3H)-ones as structural analogs of fluorophoric 6-aryl- and 6,7-diaryl-1,8-naphthalimides were studied.

Spiropyrans are a promising class of organic photochromic compounds that are currently of great interest, especially in the fields of molecular electronics, chemosensing, photopharmacology and theranostics. One of the key challenges hindering the widespread practical application of these compounds involves enhancing the stability of the active form and shifting its absorption maximum toward the far-red or even near-infrared (NIR) region of the spectrum. In this study, a series of new spiropyran derivatives with elongated conjugation chains and halogen atoms was obtained. These derivatives exhibit exceptional spectral and kinetic properties, such as NIR-absorption and emission, as well as an extended lifetime of the active form. Of particular interest is the complex case of multiple electronic effects observed in these compounds, which was extensively studied by theoretical modeling. Additionally, we conducted initial photodriven toxicity studies of target compounds using bacterial lux-biosensors, which confirmed their potential as theranostic agents. The results obtained provide valuable insights into the structural factors that determine the properties of spiropyrans, contributing to the rational design of photochromic compounds for various applications.

Novel double aza- and diaza[4,5]helicenes, the two helical units of which have a common naphthalene core, have been prepared through a five-step synthetic sequence using commercially available 2,3-dihaloazines (2,3-dibromopyridine, 2,3-dichloropyrazine and 2,3-dichloroquinoxaline) as starting materials. The X-ray structures, UV-vis absorption and fluorescence spectra of the helicenes were investigated and compared to those of the parent phenanthrene, single aza[4]- and [5]carbohelicenes, and a double [4,5]carbohelicene.

Chromo-fluorogenic phenomena, well investigated in certain phase states of a substance, become a subject of interest for studying the possibility of their manifestation in several phase states, as well as during the transition from one phase state to another. Synthesis methods have been developed and several derivatives of 6-nitro(formyl)-8-formyl(nitro)spirobenzopyran-indoline have been obtained, which is a molecular platform that makes it possible to realise a number of unique properties, including the barochromic effect in the gas phase, dual-state photochromism, dual-state photochromic cycle and highly efficient fluorescent molecular switches in solution. When studying the barochromic effect, the criteria for a molecular platform that determine the possibility of its manifestation were determined.

Photopharmacology is a young and rapidly developing field of research that offers significant potential for new insights into targeted therapy. While it primarily focuses on cancer treatment, it also holds promise for other diseases. The key feature of photopharmacological agents is the presence of a photosensitive and biologically active component in the same molecule. In our current study, we synthesized a spiropyran-based meta-stable state photoacid containing a fragment of β-estradiol. This compound exhibits negative photochromism and photocontrolled fluorescence under visible-light irradiation due to the initial stabilization of its self-protonated form in solution. We conducted comprehensive biological studies on the HeLa cells model to assess the short- and long-term cytotoxicity of the photoacid, its metabolic effects, its influence on signaling and epithelial-mesenchymal transition super-system pathways, and the proportion of the population enriched with cancer stem cells. Our findings reveal that this derivative demonstrates low cytotoxicity to HeLa cells, yet it is capable of dramatically reducing malignant cells side population enriched in cancer stem cells. Additionally, appropriate structural modification lead to an increase in some other biological effects compared to β-estradiol. In particular, our substance possesses rare properties of AP-1 suppression and demonstrates some pro-oxidant and metabolic effects, which can be regulated by visible light irradiation. As a result, the new estradiol-based photoacid may be considered a promising multi-acting photopharmacological agent for the next-generation anti-cancer research & development.

In recent years, the introduction of one or more heteroaromatic rings into a polyaromatic backbone has attracted growing interest as it allows significant control over optical, electronic and supramolecular characteristics. Polyheteroaromatic compounds are potential optoelectronic conjugate materials due to their photo- and electrochemical properties. This work describes the structure and photophysical properties of the first representatives of azaoxahelicenes of the furoquinoline series, synthesized from readily available starting compounds. Using X-ray diffraction analysis and DFT calculations, it was established that furan-fused aza [5]helicenes, unlike their carbon analogues, do not undergo Mallory-type photocyclization due to an increase in the distance between the terminal carbon atoms, which determines their greater resistance to UV light. A study of the acidochromic properties of the obtained compounds showed that protonation with trifluoroacetic acid (TFA) leads to an increase in the fluorescence intensity of most fluorophores. The best fluorescence enhancement was obtained for a fluorophore containing a methoxy substituent in the peripheral phenyl moiety, with a 10-fold increase in quantum yield. The introduction of a furoquinoline residue into the helicene skeleton leads to an improvement in fluorescent properties, as well as the possibility of their modulation by acidic agents. In the future, the first representatives of azaoxahelicenes of the naphthofuroquinoline series will be used to design new materials for optoelectronics and study their performance properties.

An efficient approach to the synthesis of novel 2,3-diaryl-3,4-dihydro-2H-benzo[4,5]imidazo[2,1-b][1,3,4]thiadiazines via a base-catalyzed intramolecular cyclization of 2-arylmethylthio-N-arylidene-1H-benzo[d]imidazol-1-amines has been developed. The use of alkali is critical for the annulation of the thiadiazine ring. In the absence of strong bases, the starting compounds undergo deamination with elimination of benzonitrile and formation of 2-arylmethylthiobenzimidazoles.

By the condensation of 4-amino-5-R-2,4-dihydro-3H-1,2,4-triazole-3-thiones with anthracene-9- carbaldehyde, respective 4-[(anthracene-9′-ylmethylene)amine)]-5-R-2,4-dihydro-3H-1,2,4-triazole-3-thiones are prepared and structurally characterized by NMR, UV, IR spectroscopies, high-resolution mass spectrometry, and single crystal XRD. The effect of a substituent at position 5 in triazole moieties of azomethines obtained on their head-to-head or head-to-tail crystal packings is determined.

Spiropyran salts containing a cationic vinyl-3H-indolium moiety are characterized by NIR absorption and fluorescence of their merocyanine forms. This feature makes them promising fluorescent probes and markers for bioimaging. The article focuses on the synthesis and study of the spectral, kinetic and toxic characteristics of such compounds with respect to various substituents in different moieties and the type of anion. A detailed analysis of the acquired data made it possible to draw some important conclusions regarding the influence of structural factors, which will be very useful for the further rational design of such derivatives. In particular, it was shown that the counterion has minimal effect on the spectral and kinetic characteristics of the dyes but dramatically affects the toxicity of the compounds. Following selection of the most appropriate compounds, bioimaging experiments were carried out to visualize planktonic bacteria and bacterial biofilms of E. coli and A. calcoaceticus. The ability to visualize biofilms is critical for the diagnosis of chronic diseases. By the results of molecular docking a theoretical interaction pattern between spiropyran molecules and DNA was proposed.

The synthesis of a new symmetric bis(spiropyran) of the indoline series existing as an equilibrium mixture of isomeric forms in various organic solvents is described. This equilibrium was in detail studied by dynamic NMR spectroscopy. In particular, the equilibrium constants were found at various temperatures, and the thermal effects of isomerization processes were calculated. The thermal transformations were studied by quantum chemical modeling. As a result, possible isomerization pathways were proposed and the observed ratio of the forms in the NMR spectra was explained. Photo- and thermochromic transformations were studied by UV spectroscopy, which revealed positive photochromic properties of the target compound. The observed changes in the absorption spectra with increasing temperature are completely consistent with the results of NMR studies. The nature of the absorption bands observed in the spectra was explained using time-dependent density functional theory (TD-DFT) calculations. The surface-enhanced Raman scattering (SERS) spectra of the synthesized compound on the surface of silver nanoparticles were detected and analyzed before and after UV irradiation to determine prospects for using similar bis(spiropyrans) as SERS markers and probes.

Recently the need for smart materials has been extremely growing, and the development of materials with appropriate characteristics has become one of the main challenges. Heptamethine cyanine dyes are widely used in theranostics and photovoltaics due to their remarkable optical properties. However, they are characterized by "rigid" non-changable properties. The main aim of the current study is to unveil correlation between structure and optical properties in the range of vinyl-3H-indolium substituted spiropyrans, which can be considered as the closest analogs of heptamethine cyanines with the photocontrolable optical and fluorescent properties. The effects of substitution in indoline and 2H-chromene cycles, as well as anion change are under the study. To achieve this goal, a series of spiropyran iodides and perchlorates with methyl, methoxy substituents or fluorine atom in position 6 ', as well as a conjugated vinyl-3H-indolium fragment in position 8 ', were synthesized. The structure of the compounds was carefully studied using SC XRD, NMR, IR and mass spectroscopy. Then, studies on absorption and photoluminescence characteristics, as well as photochromic behavior were carried out. A series of spiropyran iodides and perchlorates with methyl, methoxy and fluorine substituents in position 6 ', as well as a conjugated vinyl-3H-indolium fragment in position 8 ', were synthesized. The structure of the compounds was carefully studied using NMR, IR and mass spectroscopy, as well as SC XRD. Studies on absorption and photoluminescence characteristics, as well as photochromic behavior were carried out. image

Molecular platforms, capable of exhibiting various well-known properties, allow us to observe under certain structural modifications, due to the combination of these properties, the formation of new effects or phenomena, for example, photochromic balance. The 6-bromo-substituted spiro[indoline-pyranoquinolines] were found to exhibit the properties of photochromic balance, exhibiting both positive and negative T-type photochromism. A detailed study was carried out on the thermodynamics and kinetics of processes, the combination of which forms the effect of photochromic scales: the equilibrium of cyclic and merocyanine isomers of spiropyrans, thermal opening of the pyran ring and thermal recyclisation, and photocolouring and photobleaching of spiropyran solutions. Based on experimental data and quantum chemical modelling, directions for structural tuning have been established for the most pronounced manifestation of the effect of photochromic balances based on spiro[indoline-pyranoquinolines], which include enhancing the electron-withdrawing properties of the substituents in the pyridobenzopyran part of spiropyrans and the introduction of strong electron-donating groups into the indoline fragment.

Конденсацией 4-амино-5-R-2,4-дигидро-3H-1,2,4-триазол-3-тионов с антрацен-9-карбальдегидом были получены соответствующие 4-[(антрацен-9‵-илметилен)амин)]-5-R-2,4-дигидро-3H-1,2,4-триазол-3-тионы, которые структурно охарактеризованы с привлечением методов спектроскопии ЯМР, УФ, ИК, масс спектрометрии высокого разрешения и РСА. Установлено влияние заместителя в положении 5 триазольного фрагмента полученных азометинов на их кристаллическую упаковку «голова к голове» или «голова к хвосту».

Spiropyrans modified with reactive polyfunctional substituents are of great interest as building blocks for the creation of various smart systems with controllable properties for materials science and biomedicine. In this study, a new highly modified spiropyran of the indoline series, methyl 5′-chloro-8-formyl-5-hydroxy-1′,3′,3′-trimethyl-spiro[chromene-2,2′-indoline]-6-carboxylate, was obtained via the cyclocondensation reaction from 5-chloro-1,2,3,3-tetramethyl-3H-indolium perchlorate and methyl 3,5-diformyl-2,4-dihydroxy-benzoate. The molecular structure of the target compound was confirmed by 1H, 13C NMR, and IR spectroscopy, as well as LC/MS and elemental analysis. Photochemical studies revealed photochromic activity for the obtained spiropyran at room temperature. The photoinduced merocyanine form demonstrated an enhanced lifetime and fluorescent properties in the red region of the spectrum.

4-Bromo- and 4,5-dibromo-1,8-bis(dimethylamino)naphthalenes were arylated with arylboronic acids under Suzuki reaction conditions to provide 4-aryl- and 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes, respectively. The interaction of 4,5-dibromo-1,8-bis(dimethylamino)naphthalene with pyridin-3-ylboronic acid was accompanied by heterocyclization leading unexpectedly to the formation of N3,N3,N4,N4-tetramethylacenaphtho[1,2-b]pyridine-3,4-diamine. Dynamic 1H NMR experiments showed fast interconversion between syn and anti conformers of 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes in CDCl3 solution at room temperature. The free energy of the rotational isomerization was determined to be ∼14.0 kcal mol-1 for 4,5-di(m-tolyl) and 4,5-di(naphthalen-2-yl) derivatives. X-ray analysis of 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes revealed a high degree of structural deformation due to internal steric repulsions between both peri-dimethylamino and peri-aryl groups. In crystals, 4,5-di(naphthalen-1-yl)-1,8-bis(dimethylamino)naphthalene molecules exist exclusively in the most stable anti-out form, while for 4,5-di(naphthalen-2-yl) and 4,5-di(m-tolyl) counterparts, only the syn-form is realized. The introduction of two peri-aryl substituents in the 1,8-bis(dimethylamino)naphthalene scaffold affected the basic properties, making the 4,5-diphenyl derivative 0.7 pKa units less basic. The protonation of 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes leads to dramatic changes in their structures. Compared to the corresponding bases, the inter-nitrogen distance in these salts noticeably decreases whereas peri-aromatic rings move away from each other demonstrating the so-called "clothespin effect". This lowers the barriers of syn/anti-isomerization; as a result, protonated molecules with peri-m-tolyl and even peri-(naphthalen-2-yl) substituents exist in crystals as mixtures of rotamers.

The S(O,N)-benzyl ethers of N-arylquinone imines undergo cyclization under the action of bases to form products of the benzothiazol, benzoxazole, and benzimidazole series, while under thermal conditions they undergo a non-catalyzed rearrangement to form spiro-cyclohexadiene derivatives of benzazines. The benzimidazole, spirobenzothiazine, and spirobenzoxazine structures were supported by the x-ray diffraction method. The possibility of intramolecular photochemical cyclization was investigated; ortho-S(O,N)-benzyl-substituted N-arylquinone imines show high photostability under UV irradiation. The features of the cyclization processes of quinone imine derivatives were revealed by DFT calculations using the wB97XD/6-311++G** method.