Crown Ether Styryl Dyes Research Articles

Supramolecular Dimerization and [2 + 2] Photocycloaddition Reactions of Crown Ether Styryl Dyes Containing a Tethered Ammonium Group: Structure-Property Relationships.

Molecular self-assembly is an effective strategy for controlling the [2 + 2] photocycloaddition reaction of olefins. The geometrical properties of supramolecular assemblies are proven to have a critical effect on the efficiency and selectivity of this photoreaction both in the solid state and in solution, but the role of other factors remains poorly understood. Convenient supramolecular systems to study the structure-property relationships are pseudocyclic dimers spontaneously formed by styryl dyes containing a crown ether moiety and a remote ammonium group. New dyes of this type were synthesized to investigate the effects of structural and electronic factors on the quantitative characteristics of supramolecular dimerization and [2 + 2] photocycloaddition in solution. Variable structural parameters for the styryl dyes were the size and structure of macrocyclic moiety, the nature of heteroaromatic residue, and the length of the ammonioalkyl group attached to this residue. Quantum chemical calculations of the pseudocyclic dimers were performed in order to interpret the relationships between the structure of the ammonium dyes and the efficiency of the supramolecular photoreaction. One of the dimeric complexes was obtained in the crystalline state and studied by X-ray diffraction. The results obtained demonstrate that the photocycloaddition in the pseudocyclic dimers can be dramatically affected by the electronic structure of the styryl moieties, as dependent on the electron-donating ability of the substituents on the benzene ring, and by the conformational flexibility of the pseudocycle, which determines the mobility of the olefinic bonds. The significance of electronic factors is highlighted by the fact that the photocycloaddition quantum yield in geometrically similar dimeric structures varies from ≤10(-4) to 0.38. The latter value is unusually high for olefins in solution.

Synthesis, Structure, and Properties of Supramolecular Photoswitches Based on Ammonioalkyl Derivatives of Crown Ether Styryl Dyes

The synthesis of new styryl dyes derived from 4-pyridine and 4-quinoline and having an ammonioalkyl N-substituent and benzocrown ether moieties of different sizes and with different sets of heteroatoms was developed. Spontaneous "head-to-tail" dimerization of these dyes via the formation of numerous hydrogen bonds between the terminal NH3(+) groups and crown ether moieties was detected in MeCN solutions. The stability constants of the dimeric complexes having pseudocyclic structure were studied by (1)H NMR titration. The most stable complexes (log Kd up to 8.2) were found in the case of dyes with the 18-crown-6 ether moiety, which is most complementary for binding a primary ammonium group. Stacking interaction of the conjugated systems in the dimeric complexes contributes to their stability to a much lesser extent. In dimeric complexes, the ethylene bonds of the dyes are preorganized for stereospecific [2 + 2] photocycloaddition (PCA) induced by visible light. PCA yields only rctt isomers of bis-crown-containing cyclobutane derivatives. The dyes were studied by X-ray diffraction; it was found that the dimeric arrangement is also retained in the crystalline state. The possibility of topochemical PCA of the dyes in single crystals without their destruction was demonstrated. The possibility of retro-PCA of the obtained cyclobutane derivatives to give the starting dyes was shown. The elucidated regularities of PCA can be used to fabricate optical data recording systems based on ammonioalkyl derivatives of crown ether styryl dyes.

Formation of dimeric and cation-‘capped’ complexes by crown-ether styryl dyes: A DFT and X-ray study

DFT calculations for the benzothiazole styryl dyes containing a benzo-18-crown-6-ether fragment and an ammonioalkyl or ammonio- p-xylylenyl substituent at the quaternary nitrogen atom of the benzothiazolium residue were carried out. The effect of the length and rigidity of the N-substituent on the structure and the formation energy of the cation-‘capped’ Z isomers of the dyes arising on exposure to light as a result of intramolecular interaction involving the hydrogen bonds of the N-substituent ammonium group (spacer) with the oxygen atoms of the crown-ether fragment was studied. It was found that the dyes in solution are likely to exist predominantly as ion pairs with one perchlorate anion and the most pronounced stabilization of cation-‘capped’ complexes is attained for dyes having rather long ammoniohexyl or ammonio- p-xylylenyl spacer. The DFT results are in good agreement with X-ray diffraction data for the dimeric complex of the dye with an N-ammoniohexyl substituent.

Cucurbit[7]uril Complexes of Crown-Ether Derived Styryl and (Bis)styryl Dyes

In this paper, we report the interaction of the CB[7] molecular container with crown ether styryl and (bis)styryl dyes 1-6. The interaction of monostyryl dyes (1 and 2) with CB[7] results in the formation of 1:1 complexes where the CB[7] molecule is located on the region of the guest encompassing the pyridinium ring, C=C double bond, and a portion of the aryl ring of benzocrown ethers 1 and 2. For (bis)styryl dyes (3-5), the formation of two types of complexes with composition dye.CB[7].dye and CB[7].dye.CB[7] was confirmed by a combination of optical and electrospray ionization mass spectroscopy (ESI-MS) methods. In the case of (bis)styryl dye (6), both 2:1 and 1:1 compositions 6.CB[7].6 and CB[7].6 were formed. Complex formation is accompanied by substantial changes in the optical characteristics of the dyes and formation of long-lived excimer species. We tested the stimuli responsiveness of this system in response to metal ions. We find that the metal ions prefer to bind to the electrostatically negative ureidyl C=O portals of the CB[7] rather than with the crown ether moiety of the styryl dyes.

Polymer films with an amphiphilic crown-ether styryl dye as a prototype of chemosensing materials

A combination of the photosensitive and ion-selective properties of thin polymer films with immobilised amphiphilic crown-ether styryl dye (in particular dye interaction with alkaline earth metal ions) gives evidence that such films can serve as a prototype of chemosensors with optical signal detection.

Synthesis and Fluorescence Properties of a Novel Supramolecular Complex Containing [60]Fullerene Moiety

A new crown ether styryl dye containing [60]Fullerene moiety has been synthesized, and characterized by FT-IR, NMR and Mass spectra. Fluorescence spectra of the compound have also been studied. The results indicate a strong hypsochromic shift from 548 nm to 526 nm is observed on cation complexation, and the intensity of peaks at 504 nm, 548 nm and 590 nm decrease as the metal cation concentration is increased at 77K.

Crown ether styryl dyes

Regio- and stereoselectivity of [2+2]-photocycloaddition in complexes containing crown ether styryl dyes and alkaline-earth metal cations were studied using molecular mechanics. The main assumption is that the rate of the allowed concerted photocycloaddition correlates with the relative energies of the ground states of dimeric adducts, which are treated as pre-reaction complexes, and the resulting cyclobutanes. These energies are estimated by molecular mechanics within the MMX parameterization. The calculated characteristics of different dyes are studied as functions of the structure of the heterocyclic moiety, the structure and size of the N-substituent, the size of the crown ether cycle, and the nature of the metal cation. A comparison between the computational results and the experimental data showed that the observed quantum yield of the reaction is governed by the relative energies of the dimeric complexes and the resulting cyclobutanes as well as by the mutual arrangement of dye molecules in the dimeric complexes. Both factors are closely interrelated. The approach used in this work furnishes an explanation for the experimental data and provides a guideline for supramolecular control of regio- and stereochemistry of cation-dependent [2+2]-photocycloaddition.

ChemInform Abstract: Crown Ether Styryl Dyes. Part 24. Synthesis of Multiphotochromic 15‐Crown‐5 Ethers with Rigid Spacers, Their Anion‐Capped Complexes, and Stereospecific [2 + 2] Autophotocycloaddition.

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Monolayers of an amphiphilic crown-ether styryl dye

The crown-ether styryl dye ( I) was synthesized and its monolayers were prepared. The surface-active and optical properties of dye I were investigated. The surface pressure-molecular area and surface potential-molecular area isotherms for mixed monolayers of dye I and dipalmitoylphosphatidic acid at various aqueous salt subphases were measured.

ChemInform Abstract: Crown Ether Styryl Dyes. Part 22. Synthesis and Complexation of the cis‐Isomers of the Photochromic Aza‐15‐crown‐5‐ethers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Crown Ether Styryl Dyes. Part 20. Synthesis, Spectral Properties, and Complex Formation of Photochromic Dyes Based on a 15‐Crown‐5‐ substituted Benzothiazole (cf. (IV)).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Crown Ether Styryl Dyes. Part 21. Synthesis, Spectral Properties, and Complex Formation of trans‐Isomers of the Chromogenic Dithia‐15(18)‐ crown‐5(6)‐ethers (cf. (III)).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Nondisturbing and Stable SERS-Active Substrates with Increased Contribution of Long-Range Component of Raman Enhancement Created by High-Temperature Annealing of Thick Metal Films

High-temperature annealing of thick silver films (TSFs) deposited onto a smooth dielectric substrate leads to high-order self-organization of metal clusters on the film surface. A comparative atomic force microscopic (AFM) analysis of “as-deposited” and annealed TSFs (aTSFs) shows that uniform ellipsoidal roughness ∼41 × 25 nm in lateral cross section and ∼45 nm in height results after annealing. These metal clusters are mutually oriented so that the main lateral axes of the ellipsoids are nearly parallel. UV−visible data demonstrate a ∼300 nm hypsocromic shift of the bands corresponding to the collective surface plasmon modes. Additionally, a new (∼350 nm) band related to the normal component of the plasmon oscillations appears after annealing. This band was found to be strongly angle-dependent for p-polarized light. The aTSFs appeared extremely time- and organic solvent-stable versus as-deposited films. The aTSFs were found to be nondisturbing surface-enhanced Raman scattering (SERS)-active substrates in the application to studies of complexation of crown ether styryl dyes with metal ions. A pronounced SERS signal of the analyte rhodamine 6G was observed with aTSFs, even when the analyte was separated from the silver surface with five Langmuir−Blodgett monolayers of stearic acid. At the same time, depositing only a monolayer of stearic acid on the as-deposited film completely suppressed the SERS signal of the analyte. Finally, the self-assembling of Ag clusters on the surface of the aTSF, stimulated by the high-temperature annealing, results in the creation of a time- and organic solvent-stable SERS substrate with nanometer-scale quasi-periodical roughness, and this substrate exhibits an increased contribution of the electromagnetic component to the overall Raman enhancement.

Photosensitive supramolecular systems based on amphiphilic crown ethers

An amphiphilic crown-ether styryl dye was synthesized and its properties at the interfaces were investigated. This dye, which in monolayers interacts with some cations and shows reversible changes of the light reflection after photoactivation near the absorption maximum, is an excellent component of functional organized systems.

Complexation of Photochromic Crown Ether Styryl Dyes with Mg2+ As Probed by Surface-Enhanced Raman Scattering Spectroscopy

Complexation with magnesium cations of 2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin (1), as well as derivatives of crown ether styryl dyes perchlorate 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-ethylbenzothiazolium (2), betaine 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-(3-sulfopropyl)benzothiazolium (3), betaine 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-(3-sulfoethyl)benzothiazolium (4) was studied by surface-enhanced Raman scattering (SERS) spectroscopy. Comparative studies of isomerization and complexation of photochromic ionophores 2−4 with Mg2+ in solution and when adsorbed on the silver surface were performed. The aim was to characterize parameters of these processes depending on the nature (alkyl versus sulfo-alkyl) as well as the length (sulfoethyl versus sulfopropyl) of the N substituent in the benzothiazolium residue. The data obtained indicate stabilization of the trans conformation and prevention of the trans−cis isomerization for the adsorbed molecules as well as for their complexes with Mg2+ due to fast nonradiative energy transfer from the dye excited state to metal surface. Adsorption of a dye having initially cis conformation in solution is accompanied by surface-induced cis−trans relaxation. Adsorption constants calculated from the Langmuir isotherms revealed slightly preferential adsorption of 2−4 complexed with Mg2+ as compared to the free dyes. Desorption of the dyes was found to occur on the hours time scale, whereas reversible capture/release of metal ions by adsorbed molecules is quite fast and may serve as an indicator of a cation level and/or complexation processes in bulk solution. The SERS titration procedure was developed permitting the complexation of the ionophores with metal cations to be followed and equilibrium constants of these processes to be measured in a wide range (down to 10-7 M) of ligand concentrations. By the measurement of the equilibrium constants, adsorption on the silver surface was concluded not to affect the complexation of 1 and trans-2 with Mg2+. Association of the Mg2+ cation with the sulfonate group was found to be more favorable than binding with the crown ether moiety for the adsorbed (trans-3)Mg2+ and (trans-4)Mg2+ complexes. Appearance of the (trans-3)(Mg2+)2 and (trans-4)(Mg2+)2 species was detected in the solution at increased metal/ligand molar ratios. These complexes were found to be unperturbed if absorbed on the silver surface. Since the measurement of equilibrium constants are intractable by other techniques, measuring equilibrium constants for (trans-3)(Mg2+)2 and (trans-4)(Mg2+)2 complexe formation is readily acquired by SERS spectroscopy.

Aggregation and photoisomerization of amphiphilic crown-ether styryl dye in monolayers at the interface

The molecules oftrans-isomer of styryl dye1a, containing the benzo-18-crown-6 moiety and the methoxybenzothiazole residue with theN-octadecyl substituent, were shown to form stable, highly ordered monolayers at the water/air interface. Increasing the surface pressure of the monolayer results in the formation of the H-aggregated molecules of compound1a. The H-aggregates tend to dissociate to the monomerictrans-form, when the monolayer forms in the Langmuir-Blodgett film (LB film). The light irradiation of the LB films leads to the partially reversibletrans-cis-photoisomerization of compound1a, whose efficiency is much lower than that observed in an acetonitrile solution of1a. The aggregation of cis-1a isomers in the LB film is suggested to hamper the reversecis-trans-isomerization. The aggregation oftrans-1a molecules in the LB films does not occur in air, but, after dipping in an aqueous solution, molecules of the LB film slowly form J-aggregates. A model of the structural organization oftrans-1a molecules in the LB films was proposed.

ChemInform Abstract: Crown Ether Styryl Dyes. Part 18. Synthesis, Anion‐“Capped” Complexes, and Ion‐Selective Stereospecific (2 + 2) Autophotocycloaddition of Photochromic 18‐Crown‐6‐ethers (V).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Crown Ether Styryl Dyes. Part 15. Synthesis and Two Pathways for Regio‐ and Stereospecific Cation‐Dependent (2 + 2)‐Autophotocycloaddition of Chromogenic 15‐Crown‐5 Betaines in the Quinoline Series.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Crown Ether Styryl Dyes. Part 14. Synthesis, Luminescence and Complex Formation of trans‐Isomers of Chromogenic 15‐Crown‐5‐ether.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Surface-Enhanced Resonance Raman Spectra of Photochromic Crown Ether Styryl Dyes, Their Model Chromophores, and Their Complexes with Mg2+

The complexation of the derivatives of crown ether styryl dyes betaine 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-(3-sulfopropyl)benzothiazolium (1a) and perchlorate 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-ethylbenzothiazolium (1b) and their molecular fragment 2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin (2) with magnesium cations has been studied by the surface-enhanced Raman scattering (SERS) spectroscopy at very low (down to 10-8 M) concentrations. A detailed comparison of the Raman and SERS spectra of 1a,b and their molecular fragments 2 and perchlorate 2-Me-3-ethyl benzothiazolium (3) enabled one to assign the vibrational modes and propose the model of dye interaction with the silver SERS-active surface. Benzo-15-crown-5 chromophore of 1a,b was found to be adsorbed through its crown ether part so that the plane of benzene ring is nearly perpendicular to the surface of silver electrode. The CC bond as well as the benzothiazolium chromophore being situated far from the electrode surface does not contribute noticeably to the SERS spectra. The sulfonate group of 1a and alkyl group of 1b do not affect the geometry of adsorption. The SERS spectra of trans-1a,b and their complexes with Mg2+ are observed selectively studying the photostationary mixtures of cis and trans isomers. The complexation of Mg2+ leads to the remarkable frequency shifts of several bands associated primarily with the benzo-15-crown-5 fragment of 1a,b. The spectral effects which reflect the cation-induced intramolecular electron transfer were found to be very similar in both resonance Raman and SERS spectra of the dyes. Hence, the adsorption on the surface of silver electrode does not perturb the complexation of the dyes with Mg2+. The results demonstrate that the SERS spectroscopy enables one to study the complexation of the photochromic crown ether styryl dyes with the metal cations, ensuring selective detection of trans isomers and high sensitivity to structural changes of the dyes in a wide range of concentrations.