Novel conjugates of rhodamine B with 2-chloro-, 2-chloro-6-methyl-and 2-chloro-6-methoxyquinoline were synthesized. Their structure and ion-induced switching properties were studied using 1 & Ncy;, COSY, 13 & Scy;, HSQC and HMBC NMR, UV-Vis/fluorescence spectroscopy, X-ray diffraction analysis and DFT quantum chemical calculations. The compounds obtained exist in the spirolactam form, which is characterized by the lack of absorption in the region > 500 nm and the absence of emission properties. However, in the presence of Hg2+ cations, they exhibit a selective and contrasting naked eye effect, as a result of which the colorless acetonitrile solution becomes purple. Simultaneously, the appearance of intense emission at 584-588 nm is observed. These changes are due to the opening of the spirocycle, which was confirmed by an additional 1H NMR experiment. The reverse transformation occurs under the action of CN-anions. The observed ion-controlled off-on-off switching of the fluorescence properties was used to develop the logic circuit. For the first time, using PCM/DFT/M06-2X-D3/ Def2-SVP calculations in acetonitrile and AIM analysis, it was shown that the interaction with mercury(II) cations is a multistage process.

The photochromic behavior of N-acetyl (2) and N-propionyl (3) derivatives of 2-((phenylamino)methylene)benzo[b]thiophen-3(2H)-one was investigated in both the solid state and in solution using IR, 1H, 13C NMR spectroscopy, high-resolution mass spectrometry, UV-Vis/fluorescence spectroscopy, and X-ray diffraction analysis, complemented by DFT quantum chemical calculations. Solid-state irradiation of N-acetyl derivative 2 triggers [2+2] photocycloaddition to yield dimer 4, whereas the N-propionyl analog 3 remains photostable under these conditions. Conversely, in acetonitrile solution, irradiation of both 2 and 3 with light of 436 nm induces a multi-step 1,5-sigmatropic N→O acyl migration, resulting in the formation of O-acetyl 5 and O-propionyl 6 isomers. DFT calculations at the M06-2X/Def2-TZVP level, incorporating the PCM solvation model and AIM analysis, were successfully utilized to rationalize the observed phase-dependent photochemical phenomena.

A series of previously unknown coumarin-rhodamine derivatives was synthesized. The resulting compounds exhibit long-wavelength absorption in the range of 408–443 nm in acetonitrile. However, the presence of a methyl group in the bridge connecting the coumarin and rhodamine fragments of the molecule leads to a hypsochromic shift to 310 nm due to a steric effect that weakens conjugation. The obtained compounds exist in the cyclic spirolactam form, which is further confirmed by the absence of fluorescence above 520 nm. The ionochromic and sensory properties of coumarin-rhodamines were studied in the presence of d-metal cations in acetonitrile solutions. A highly selective interaction of the obtained compounds with Hg2+ cations was discovered, accompanied by the appearance of a characteristic red color due to the appearance of new absorption maxima in the region of 560 nm, as well as the appearance of intense fluorescence at 580-584 nm. This spectral response is due to the cation-induced opening of the spirolactam ring. Furthermore, the addition of cyanide ions (CN⁻) to the in situ formed Hg2+ complexes initiates a selective reverse isomerization back to the non-fluorescent spirolactam form, effectively restoring the original spectral characteristics. The described transformations can be repeated at least 4-5 times, which ensures effective modulation of the emission properties. To facilitate practical applications, test strips impregnated with the coumarin-rhodamine hybrids were developed, enabling rapid, real time and instrument-free detection of Hg2+ ions. Thus, coumarin-rhodamine derivatives can be used as effective molecular switches of optical properties, as well as in the production of materials for monitoring the composition of the environment. For citation: Dubonosov A.D., Nikolaeva O.G., Popov L.D., Shepelenko Е.N., Dubonosova I.V., Bren V.A. Synthesis, ionochromic properties of coumarin-rhodamine derivatives and their application in test strips. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2026. V. 69. N 8. P. 25-32. DOI: 10.6060/ivkkt.20266908.7005.

New photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophen-3(2H)-ones containing a terpyridine receptor have been synthesized. They absorb in the visible region of the spectrum at 423-426 nm and exhibit emission at 463-468 nm. Their irradiation in acetonitrile with light of 436 nm leads to a multi-stage rearrangement, including Z/E isomerization about the C--C bond, N -> O migration of the acyl group and the formation of non-emissive O-acylated E-isomers, which were isolated preparatively. Their structure was established unambiguously by IR, 1H, 13C NMR spectroscopy and HR mass spectrometry. The reverse thermal reaction with O -> N migration of the acyl group is catalyzed by acid catalysts. N-Acylated compounds in acetonitrile selectively form non-fluorescent complexes with Fe2+ cations, which is accompanied by the naked-eye effect with changing the color from yellow to maroon. A successful selective interaction with AcO- led to the restoration of the initial absorption and emission properties. Density functional theory (DFT) calculations at the M06-2X/def2TZVP level with the PCM solvation method were used to explain the observed photoisomerizations and ionochromic transformations. The obtained compounds represent multifunctional on-off-on molecular switches of optical and fluorescent properties upon sequential exposure to light and H+ or sequential addition of Fe2+ and AcO- ions. A combinatorial logic gate was designed based on the basis of these switching properties.

Bifunctional hybrids of a new type containing photochromic indolyl(thienyl) diarylethenes with a pyrroldione bridge directly linked by a dimethylene spacer to an ionochromic rhodamine moiety were synthesized. The synthesized hybrids in toluene exhibit absorption at 450-455 nm and fluorescence at 560 nm. Irradiation with UV light leads to the formation of ring-closed non-fluorescent diarylethene isomeric fragments. Under visible light (or gradually in the dark conditions), reverse isomerization to the initial forms occurs. The spectral and kinetic characteristics of the processes have been studied. In the presence of H+ cation, a striking naked eye effect is observed due to the opening of the rhodamine-spirolactam ring and appearance of a characteristic pink-crimson coloration at 561 nm along with intense long-wavelength emission at 586 nm. This process is completely reversible upon exposure to triethylamine. The mechanism of this transformation was confirmed by additional 1H and 13C NMR experiments. The M06-2X/Def2-TZVP method and AIM analysis were successfully used to explain observed light-induced isomerizations as well as proton-induced transformations. Thus, revers-ible switching of the fluorescent properties of hybrid molecules can be operated by light irradiation and proton.

A series of novel photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline receptor substituent was synthesized. Upon irradiation in acetonitrile or DMSO with light of 436 nm, they underwent Z–E isomerization of the C=C bond, followed by very fast N→O migration of the acyl group and the formation of nonemissive O-acylated isomers. These isomers were isolated preparatively and fully characterized by IR, 1H, and 13C NMR spectroscopy as well as HRMS and XRD methods. The reverse thermal reaction was catalyzed by protonic acids. N-Acylated compounds exclusively with Fe2+ formed nonfluorescent complexes with a contrast naked-eye effect: a color change of the solutions from yellow to dark orange. Subsequent selective interaction with AcO− led to the restoration of the initial absorption and emission properties. Thus, the obtained compounds represent dual-mode “on–off–on” switches of optical and fluorescent properties under sequential exposure to light and H+ or sequential addition of Fe2+ and AcO− ions.

Синтезирована серия кумарин-терпиридиновых иминных конъюгатов. Полученные соединения обладают флуоресценцией в районе 504-568 нм с большой величиной сдвига Стокса (9050-12500 см-1), обусловленной быстрым внутримолекулярным О->N переносом протона в возбужденном состоянии с образованием короткоживущего кетоаминного изомера. Они представляют собой полифункциональные ионохромные naked-eye-системы, способные к детектированию катионов Fe2+ за счет комплексообразования с терпиридиновым фрагментом (изменение окраски раствора со светло-желтой на малиновую) и Zn2+ (комплексообразование по о-гидроксииминовому фрагменту). При этом наблюдается уменьшение интенсивности исходной эмиссии конъюгатов до нулевых значений или появление интенсивной флуоресценции комплекса с цинком(II). Кроме того, кумарин-терпиридиновые конъюгаты селективно реагируют на фторид и цианид-анионы с изменением окраски раствора со светло-желтой на оранжевую. Таким образом, полученные соединения представляют собой удобную платформу для разработки хромогенных и флуорогенных сенсоров для определения катионов и анионов. Авторы благодарны ЦКП «Нанотехнологии» ЮРГПУ (НИИ) за проведение ЯМР-экспериментов.

A series of rhodamine 6G derivatives with o-hydroxyarylimine substituents have been synthesized. The obtained compounds in acetonitrile have been found capable of the H+-induced transformation of the spirolactam form into the open one. The process has been accompanied by the formation of a new long-wave absorption maximums at 527–529 nm and fluorescence bands at 557–560 nm. The compound containing 2-hydroxy-4-dimethylaminophenyl substituent has exhibited switching of emission at 429 nm in the presence of Zn2+ cations. This fluorescence has been quenched selectively by the CN− anions. Copper(II) cations have caused the transformation of the spiro structure of rhodamine bearing 2-hydroxy-3-tert-butylbenzofuran group into the open form. The isomerization has been accompanied by chromogenic naked-eye effect: change in the solution color from pale yellow to pink and the appearance of fluorescence at 556 nm. The observed ion-induced spectral transformations can be used in the design of optical and fluorescent chemosensors.

Diarylethenes containing coumarin and thiophene substituents in the thiazole bridge and quinoline receptor fragments have been synthesized. 2-Chloroquinoline diarylethenes have afforded colored cyclic hexadiene forms under UV irradiation, which have undergone reverse isomerization when exposed to visible light. 2-Hydroxyquinoline diarylethenes have been found nonphotochromic. The ionochromic effects of interaction with fluoride anions as well as copper(II) and nickel(II) cations have been studied.

Синтезированы имины 4-формил-3-гидрокси-2-нафтойной кислоты. Исследованы их спектрально-люминесцентные и ионохромные свойства. В спектрах ариламинов в ацетонитриле наблюдается небольшой гипсохромный сдвиг полосы поглощения при добавлении катионов d-металлов без заметного изменения окраски раствора. Спектры испускания близки к исходным спектрам флуоресценции лигандов, лишь в случае иона меди(II) наблюдается практически полное тушение флуоресценции. Бензилимин демонстрирует селективное относительное увеличение интенсивности эмиссии I/I0 в 180 раз в присутствии катионов цинка. Все синтезированные имины проявляют отчетливый «naked-eye» эффект с изменением ярко-желтого цвета раствора на бледно-желтый в случае фторид- и цианид-анионов, тогда как остальные анионы незначительно влияют на характер абсорбции. В случае бензилимина отмечены рекордные значения относительного увеличения интенсивности эмиссии I/I0 – 470 и 575 для цианид- и фторид-анионов соответственно. Таким образом, бензилимин 4-формил-3-гидрокси-2-нафтойной кислоты представляет собой эффективный и селективный полифункциональный флуоресцентный сенсор для детектирования ионов Zn, F и CN.

A series of N-acylated 2-aminomethylenebenzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline receptor substituent was synthesized. Upon irradiation in CH3CN or DMSO with light of 436 nm, they undergo Z/E isomerization around the C=C bond followed by rapid N→O migration of the acyl group and the formation of non-emissive O-acylated isomers. These isomers were separated preparatively and fully characterized by IR, 1H, 13C NMR, HRMS and XRD methods. The reverse thermal reaction is catalyzed by protonic acids. N-Acylated compounds exclusively with Fe2+ ions form non-fluorescent complexes with a contrast naked eye effect - color change of the solutions from yellow to pink-crimson. Subsequent selective interaction with acetate anions leads to the restoration of the initial absorption and emission spectra. Thus, the obtained compounds represent dual-mode “on-off-on” switches of optical and fluorescent properties under sequential exposure to light/H+ or sequential addition of Fe2+/AcO- ions.

Novel "naked eye" chromofluorogenic chemosensors for biologically important anions F-, CN-, AcO- and H2PO4- based on 5-chloro-2-hydroxy- (1), 3,5-dichloro-2-hydroxy- (2) and 3-bromo-2-hydroxy-5-methoxybenzylidene (3) azomethine imines were synthesized. Their structure and sensing properties were studied using H-1, COSY, C-13, HSQC, HMBC and N-15 NMR, UV-Vis/fluorescence spectroscopy, X-ray diffraction analysis and DFT calculations. Compounds 1-3 exhibit low-intensity emission at 537-574 nm with an anomalous Stokes shift of 7830-8420 cm(-1). In the presence of F-, CN-, AcO- and H2PO4- ions, this emission is completely quenched and a new intense fluorescence appears at 540-590 nm with values of the relative enhancement in fluorescence intensity (I/I-0) 15-79 ((F)-) and 10-137 (CN-). Simultaneously "naked-eye" chromogenic effect is observed with a color change from pale yellow to intense yellow or orange. These spectral responses were attributed to the OH center dot center dot center dot An(-) bonding up to the deprotonation. The association constants found for fluoride anion are 5.5 x 10(8) M-2 (1), 1.3 x 10(3) M-1 (2) and 5.3 x10(8) M-2 (3), and to cyanide anion - 2.8 x 10(3) M-1 (1), 2.0 x 10(3) M-1 (2) and 2.8 x 10(3) M-1 (3). UV-Vis limits of detection for the F- ion are 2.0-6.0 mu M (1), and for the CN- ion - 1.0-2.0 mu M. (c) 2022 Elsevier B.V. All rights reserved.

The solvent-dependent selective "naked eye " chromofluorogenic multifunctional rhodamine-based probe 3 for Al3+, Cu2+, Hg2+, S2- and CN- ions was synthesized and its spectral, luminescent and ion-ochromic properties were studied. The compound obtained exists in the spirolactam form, confirmed by data of H-1, COSY, HSQC, HMBC and C-13 NMR spectroscopy. In ethanol, Al3+ ions selectively, even in the presence of other metal cations (Na+, Ba2+, Zn2+, Cd2+, Ni2+, Co2+, Cu2+, Hg2+ and Fe3+) initiate the opening of the spirolactam ring, accompanied by the appearance of a new absorption band at 556 nm and the "naked eye " effect with a change in the yellow-green color of the solution to orange-pink. At the same time, the initial fluorescence 3 at 539 nm shifts to the longer 579 nm spectral region. The use of acetone as a solvent allows the selective detection of copper(II) cations that turn the yellow color of a solution of 3 to pink-purple (lambda(abs) 563 nm) due to the formation of the ring-open complex 3.Cu2+ that exhibits emission at 580 nm. Selective detection of Hg2+ in acetonitrile results in the "naked eye " effect characterized by a change in the color of the solution from bright yellow to pink-cherry (lambda(abs) 564 nm). The fluorescence of the mercury(II) complex is observed at 587 nm. Complexes 3.Cu2+ and 3.Hg2+ were used for the sequential selective recognition of S2- and CN- anions, respectively. A combinatorial molecular logic gate was designed based on the cation/anion sensing ability of probe 3. (c) 2022 Elsevier Ltd. All rights reserved.

A novel photochromic system based on an alkylideneisochromanedione core with heterocyclic substituents was synthesized, and its spectral luminescent and photoinduced properties were studied. The obtained iso-chromandiones containing the hexatriene fragment exist in a ring-open E-form, confirmed by the data of H-1, C-13 NMR spectroscopy and X-ray diffraction studies. The observed photoinitiated processes depend fundamentally on the nature of the heterocyclic substituents. Thiophenyl, benzo[b]thiophenyl and 1H-indolyl derivatives 5c-f are non-photochromic in the solid state, and in solutions their transformations are limited by thermally reversible E/Z-photoisomerization. Compound 5a with a furanyl substituent is photochromic in crystalline form due to the light-induced rearrangement of the ring-open hexatriene isomer into the ring-closed cyclohexadiene structure. Upon irradiation with light of 436 nm, the yellow crystals of 5a turn dark blue-green. The reverse reaction of the cycle opening and restoration of the original color of the crystals occurs extremely easily upon irradiation with visible light of 578 nm. In contrast to crystals, solutions of compounds 5a and 5b with furanyl substituents in hexane, 2-propanol, acetonitrile and DMSO are discolored when irradiated with light of 365 nm. The irreversible photorearrangement 5a,b -> 6a,b includes the stages of cyclization, the opening of the furan cycle and the formation of highly fluorescent naphthalic anhydride derivatives 6 (the quantum yield of fluorescence reaches 0.69 in hexane)), which can be used for the production of optical memory media for archive 3D discs.

A series of rhodamine B derivatives containing hydroxyimine receptor fragments was synthesized. The reaction of a 1-hydroxynaphthalene-2-carbaldehyde derivative in acetonitrile proceeds selectively with copper(II) cations and is accompanied by chromogenic naked-eye effect, a change in color from pale yellow to crimson red (λabs 548 nm) due to the cation-induced opening of the spirolactam ring, and the appearance of fluorescence in the region of 578 nm. The subsequent addition of CN– ions to the in situ formed complex leads to its selective anion-induced reverse isomerization into the spiro form, and the original spectral parameters are restored. In ethanol, o-hydroxy(dihydroxy)naphthalenecarbaldehyde derivatives selectively detect Al3+ cations that induce the rhodamine spirolactam ring opening with the attendant chromogenic naked eye effect, a change in the color of the solution from pale yellow to crimson violet, and a burst of strong fluorescence (λfl 584 nm).

Осуществлен синтез серии тиосемикарбазонов замещенных хинолин-3-карбальдегидов. 2-фенилэтинилхинолиновый тиосемикарбазон селективно ионохромен по отношению к ионам Cu и Hg в ацетонитриле. При этом бесцветный раствор окрашивается в желтый цвет, а исходная эмиссия лиганда смещается в длинноволновую область и становится более интенсивной. Тетразол[1,5-a]хинолиновое производное демонстрирует контрастный ионохромный naked-eye эффект в присутствии катионов Cd, Hg и Cu окраска раствора в случае ионов меди меняется на ярко-желтую. 2-оксо-1,2-дигидрохинолиновое производное также проявляет ионохромные свойства по отношению к указанным катионам, однако новые максимумы поглощения находятся в более коротковолновой области спектра. В присутствии ионов кадмия(II) наблюдается селективное увеличение интенсивности эмиссии (I/I) в 90 раз, что превосходит параметры чувствительности большинства известных флуоресцентных сенсоров на Cd2+. Обнаруженные закономерности свидетельствуют о большом потенциале замещенных тиосемикарбазонов в области сенсорики и могут быть использованы при создании ионохромных и флуоресцентных хемосенсоров для экспресс-анализа катионов.

Azomethine imine-coumarin mono- and bis-conjugates have been synthesized for the first time. The obtained compounds represent multifunctional chromogenic and fluorescent species capable of detecting fluoride, acetate, dihydrophosphate, and cyanide anions as well as d-metal cations (Zn2+, Pb2+, Hg2+, and Cu2+) owing to the ionochromism (the naked-eye effect) and enhancing/quenching of initial ESIPT emission with anomalous Stokes shift. The monoconjugate based on 6,7-dihydroxy-4-methyl-2-oxo-2H-chromene-8-carbaldehyde has been found capable of selective detection of CN– anions in the presence of competing F–, AcO–, H2PO4–, Cl–, NO3–, and HSO4–ions. It has exhibited selective sensor activity towards Hg2+ cations in the presence of Na+, K+, Ca2+, Ba2+, Zn2+, Cu2+, Cd2+, Ni2+, Cu2+, and Pb2+ ions.

An effective approach to the synthesis of diarylethene-amino acid hybrids DE-Gly, DE-AABA and DE-DAA (5a-d - 7-a-d) was developed via condensation of furan-2,5-dione-based diarylethenes (DE) and ethyl esters of glycine (Gly), alpha-aminobutyric acid (AABA) and D-aspartic acid (DAA) with moderate to good yields. According to X-ray diffraction data, DE-Gly hybrid 5a exists in an antiparallel conformation with a distance of 4.549 angstrom between the reactive carbon atoms C(1)-C(11), potentially capable of forming a single bond, which is suitable for the conrotatory photocyclization reaction allowed by the Woodward-Hoffman rules. The structures of the obtained compounds were proved by H-1, COZY, HSQC, HMBC and C-13 NMR spectroscopy. The hybrids DE-Gly, DE-AABA and DE-DAA absorb at 443-456 nm, which corresponds to their existence in a ring-open form O, and display fluorescence at 531-612 nm. Irradiation with light of 436 nm results in their rearrangement into ring-closed colored nonfluorescent isomers C. Backwards re-opening occurs under the action of visible light (lambda > 500 nm). Spectral kinetic investigation of 5a,c revealed that the efficiency of photocyclization, as well as the emission quantum yield, decreases with the growth of solvent polarity. The ring-closed isomer C of sterically hindered 5a (R-2 = R-3 = Me) is stable at room temperature, whereas for 5c (R-3 = H), ring opening readily occurs with the speed increasing with the polarity of the solvent. The internal emission of sterically hindered hybrids 5a, 6a and 7a (R-2 = R-3 = Me) is reversibly modulated in a binary response with good fatigue resistance under successive irradiation with light of 436 and 540 nm. (C) 2021 Elsevier B.V. All rights reserved.

Here, we report a new photosensitive metal–organic framework (MOF) that was constructed via the modification of UiO-66-NH2 with diarylethene molecules (DAE, 4-(5-Methoxy-1,2-dimethyl-1H-indol-3-yl)-3-(2,5-dimethylthiophen-3-yl)-4-furan-2,5-dione). The material that was obtained was a highly crystalline porous compound. The photoresponse of the modified MOF was observed via UV–Vis and IR spectroscopy. Most of the DAE molecules inside of the UiO-66-pores had an open conformation after synthesis. However, the equilibrium was able to be shifted further toward an open conformation using visible light irradiation with a wavelength of 520 nm. Conversely, UV-light with a wavelength of 450 nm initiated the transformation of the photoresponsive moieties inside of the pores to a closed modification. We have shown that this transformation could be used to stimulate hydrogen adsorption–desorption processes. Specifically, visible light irradiation increased the H2 capacity of modified MOF, while UV-light decreased it. A similar hybrid material with DAE moieties in the UiO-66 scaffold was applied for hydrogen storage for the first time. Additionally, the obtained results are promising for smart H2 storage that is able to be managed via light stimuli.