Search

Photophysical processes and photochemical reactions of a 15-crown-5-containing styryl dye of the pyridine series and its complexes with barium perchlorate in water in the absence and in the presence of cucurbit[7,8]urils were studied using absorption, luminescence, and laser kinetic spectroscopy. The trans—cis-photoisomerization, interconversion of the dye to the triplet state, and charge transfer were concluded to occur. The formation of a dye inclusion complex with cucurbit[7,8]urils was established.

Mono-, tri-, and pentamethine cyanine dyes containing two terminal ammonium groups in the N-substituents and bis(18-crown-6)- stilbene in MeCN form pseudocyclic 1:1 complexes (log K 1:1 up to 8.1) and triple-decker 1:2 complexes (log K 1:2 up to 2.6).

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.

Synthesis and photochromic properties of a novel spironaphtoxazine (SNO) obtained from a crown-containing dihydroisoquinoline are described. The comparison of spectral and kinetic properties with that of a crown free SNO is performed. For a crown-containing SNO, the complex formation with alkaline earth metal cations occurs both for spiro (S) and merocyanine (M) forms of the molecule. For the cations of large size (for instance, Ba 2+ ) the formation of sandwich complex was found. For a crown free SNO, only M-form complex with metal cation is possible. In all cases, the complex formation affects both on the position of the M-form absorption maximum and the M-form characteristic lifetime.

Two new styryl dyes of the benzothiazole series containing a 18-crown-6 moiety and an N -ammoniohexyl or N -ethyl substituent were synthesised. In acetonitrile, the dye bearing the ammoniohexyl linker forms a stable dimeric complex in the E -form and an intramolecular cation-‘capped’ complex in the Z -form due to ‘host–guest’ hydrogen bonding.

The electronic absorption spectra and fluorescence spectra of 4-(2-naphthyl)pyridine (1), 2-(4-methyl-2-pyridyl)-4-(2-naphthyl)pyridine (2), and 4-(2-naphthyl)-2-phenylpyridine (3) in solutions and in complexes with β-cyclodextrin (β-CD) and well water-soluble hydroxy-propyl-β-cyclodextrin (HP-β-CD) were studied. Fluorescence near 475 nm observed in aqueous solutions of compounds 1–3 arises from protonated forms of these compounds produced in the excited state. Results of DFT quantum chemical calculations show an increase in proton affinity energies of excited-state naphthylpyridines 2 and 3. The formation of inclusion complexes with cyclodextrins makes protonation of compounds 2 and 3 more difficult, which manifests in large hypsochromic shifts of fluorescence band maxima. The stability constants of the complexes 1·HP-β-CD and 2·HP-β-CD determined from their fluorescence spectra are 3425 and 3760 L mol−1, respectively. The stability constant of the complex 3·HP-β-CD (5500±600 L mol−1) was found from the changes in the solubility of naphthylpyridine 3 in water upon complexation. Semiempirical quantum chemical calculations of the molecular structures and thermodynamic characteristics of pseudorotaxane inclusion complexes of trans-2, cis-2, and trans-2·H2O with HP-β-CD were carried out.

The structures of new butadienyl dyes of the benzothiazole series containing the dithia-15-crown-5 (2a) or dithia-18-crown-6 (2b) fragments were established by X-ray diffraction. Complexation of dyes 2a,b with Hg2+, Pb2+, Cd2+, Ag+, Zn2+, and alkaline-earth cations in aqueous-acetonitrile solutions was studied by spectrophotometry. At a high percentage of water in solutions (P w ≈ 50%), these dyes have a very low ability to bind Pb2+ cations (logK < 2) and virtually do not bind Cd2+, Zn2+, and alkaline-earth cations. At the same time, these dyes form stable 1: 1 complexes with Hg2+ and Ag+ cations at all P w. The stability constants of complexes with the Ag+ cation increase with increasing P w because the free energy of hydration of this cation is much lower than the free energy of solvation in acetonitrile. In the P w range from 0 to 75%, the stability constants of the complexes of dyes 2a,b with the Hg2+ cation are larger than those of the corresponding complexes with the Ag+ cation by more than four orders of magnitude.

The novel amphiphilic butadienyl dye, containing a dimethoxybenzene unit instead of benzocrown-ether moiety (dye 1) and the amphiphilic benzodithia-15-crown-5 butadienyl dye (dye 2) form stable insoluble monolayers on distilled water. In order to evaluate the influence of the ionophore size on the molecular organisation, the known amphiphilic benzodithia-18-crown-6 butadienyl dye (dye 3) has also been used. The monolayers have been characterized by surface pressure–area and surface potential–area isotherms as well as Brewster angle microscopy and reflection spectroscopy. Besides monomers of the dyes two types of associates exist in the pure dye monolayers, i.e. dimers and aggregates. The spectroscopic properties of the monomers were obtained by studying mixed monolayers of the dyes with the lipid dimyristoyl-phosphatidylcholin (DMPC). The dimers may be organised as head-to-tail dimers with the intermolecular distances 0.38, 0.45, and 0.49 nm for dyes 1, 2, and 3, respectively. According to the extended dipole model, we propose formation of aggregates in which the chromophores are parallel to each other with the same intermolecular distances as in the dimers, and the centers of their transition moments shifted by 0.95 nm (dye 1) and 1.2 nm (dyes 2 and 3). © 2005 Elsevier B.V. All rights reserved.

Condensation of methyl-substituted six-membered heteroaromatics containing one or two nitrogen atoms with aldehyde derived from benzo-15-crown-5 ether in DMF in the presence of ButOK afforded 15-crown-5-containing hetarylphenylethenes. According to the results of NMR spectroscopy, these compounds exist as mixtures of syn and anti conformers in solution (MeCN-d3). The structures of two compounds were established by X-ray diffraction analysis.

The amphiphilic chromo-ionophore 2-[(1E,3E)-4-(2,3,5,6,8,9,11,12,14,15-decahydro-1,7,10,16,4,13-benzotetraoxadithiacyclooctadecin-18-yl)-1,3-butadienyl]-3-octadecyl-1,3-benzothiazol-3-ium perchlorate (AB211) forms mixed monolayers at the air–water interface with the phospholipid l -α-dimyristoylphosphatidylcholine (DMPC) as deduced from surface pressure–area and surface potential–area isotherms. In contrast to the behaviour of pure monolayers of AB211 on water, no association of the chromophores is observed by reflection spectroscopy. Upon compression of the mixed monolayer AB211:DMPC = 1:5, a re-orientation of the chromophores from flat to tilted is observed, presumably assisted by the stretching of the choline group of the phospholipid molecules acting a matrix.

A strong influence of the counter-anions (such as Cl− and ClO42−) on the behavior of monolayers of an amphiphilic benzodithia-18-crown-6 butadienyl dye (dye 1) on aqueous subphases containing alkali metal or heavy metal cations (K+ or Hg2+) is demonstrated for the first time. Deduced from surface pressure–area and surface potential–area isotherms, reflection spectra and Brewster angle microscopy data, dye 1 monolayers show three types of structures depending on the counter-anion's influence on chromophore association and interactions with heavy and alkali metal cations.

A procedure has been developed for the synthesis of thiaaza podands from (4′-formylbenzo)thiacrown ethers via nucleophilic regioselective opening of the macroring by the action of methylamine and methylamine hydrochloride on heating.

The inclusion complexes of the trans-isomer of2-[2-(6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxa-benzocyclopentadecen-2-yl)-vinyl]-benzothiazole(CSB) with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) were investigatedby electronic absorption and fluorescence spectroscopies in aqueous solution. Theaddition of HP-β-CD has very little effect on the absorption spectra of CSB.A 17-nm blue shift and pronounced fluorescence enhancements in the emissionspectrum of CSB were observed. 1:1 and 1:2 stoichiometries were found forcomplexes of CSB with HP-β-CD, and formation constants of the complexesand other thermodynamic parameters were estimated from fluorescence measurements.In the case of the 1:1 CSB: HP-β-CD complex, the formation constant was equalto 3,802 at 293 K, the complexation reaction was exothermic (Δ H0 = -9.2 ±1.1 kJ mol-1) and presented a positive entropy value (Δ S0 = 37.3 ± 3.8 Jmol-1 K-1). A molecular structure was proposed for the CSB:HP-beta;-CDinclusion complex.

An effective synthetic approach to the preparation of a new crown-ether vinylogs involving the Horner–Emmons olefination of carbonyl precursors with the use of C2- and C5-phosphonates was proposed. The effects of the conjugation chain length and the nature of the terminal polar functions in the phosphonate reagent on the yield and process stereoselectivity were discussed.

We studied the assembly of dithiacrown ether styryl dye (CSD) molecules in crystals, solutions, and films in the presence of metal cations. X-Ray diffraction data allowed us to conclude that the anion affects the supramolecular architecture of CSDs in the crystal, specifically, the type of stacking of the dye molecules. In solution, in the presence of Pb2+, CSD molecules with the betaine structure spontaneously form dimeric complexes consisting of two dye molecules and two metal cations, with a fixed mutual arrangement of the double bonds. The dimer complex is stable due to coordination between the anion substituent of one molecule and the metal cation located in the crown ether cavity of the other molecule. Irradiation of the dimer complexes leads to regio- and stereoselective [2 + 2]-cycloaddition, giving only one cyclobutane derivative of the eleven theoretically possible products. The other photoreaction studied for CSDs is reversible Z–E isomerization. Due to its specific structure, the betaine-type CSD is able to form the ‘anion-capped’ Z-isomer. Intramolecular coordination in the ‘anion-capped’ isomer enhances its stability and causes a sharp deceleration of its dark Z–E isomerization. The amphiphilic CSD forms relatively stable monolayers on distilled water and various aqueous salt subphases. The results obtained indicate that it is possible to distinguish between two types of the dye monolayer structures based on the presence of alkali or heavy metal cations in the aqueous subphase.

The formation of complexes between a bisstyryl dye containing two benzo-15-crown-5 ether groups, 2, and Mg2+, Ca2+, Sr2+, and Ba2+ ions was studied in acetonitrile solution by using a spectrophotometric approach. In contrast to its monostyryl analogue 1, which shows a rather low cation-binding selectivity, the bisstyryl dye 2 selectively binds the Sr2+ and Ba2+ ions because of formation of intramolecular sandwich complexes. Alkaline-earth metal cations induce substantial blue shifts of the absorption maximum of 1 and 2, particularly in the case of sandwich complex formation. The emission behavior of 1 and 2 and their Ba2+ complexes in acetonitrile solution has also been studied. In both cases, complex formation leads to a blue shift of the fluorescence maximum and a decrease in the emission quantum yield. The fluorescence decay is monoexponential for the complex of 1 and biexponential for that of 2. The longer-lived fluorescence component, which corresponds to the lower-energy band in the steady-state spe...

Bis-crown-containing styryl dyes (E,E)-2a,b having the structure and properties of molecular pincers were synthesised. In acetonitrile solution, dye (E,E)-2b is able to form intramolecular sandwich complexes with Ca2+ and Ba2+ cations. These complexes undergo E–Z-photoisomerisation and intramolecular stereoselective [2+2]-photocycloaddition to afford cyclobutane derivatives 6a,b, whose structures were studied by 1H NMR spectroscopy. Molecular-mechanics and semiempirical quantum-chemical calculations were performed to interpret experimental data.

The s-conformations of trans-1b–e were studied by 1H NMR spectroscopy in CD3CN solution. It was shown that in trans-1b–e intramolecular ion pairs between the SO3– group and the positively charged nitrogen atom of the benzothiazolium residue are formed. In the case of trans-1a no ionic association was observed. The complex formation of the trans- and cis-isomers of crown-containing styryl dyes with Mg2+ in CH3CN was studied spectrophotometrically. The anion-“capped” complexes formed by the cis-isomers were found to be more stable than the complexes formed by the corresponding trans-isomers. The stability constants of the complexes formed by the cis-isomers depend markedly on length and type of the N-substituent. Data from PM3 quantum-chemical calculations were used for the interpretation of some experimental data.

The formation of complexes between spirooxazines (SNOs) containing crown-ether and dihydroquinoline moieties and alkaline earth metal ions affects the spectral and kinetic properties of the SNO open form.

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.

A new bis(styryl) dye of the pyridine series containing two 18-crown-6 ether fragments forms a pseudocyclic complex with the 1,3-diammoniumpropane dication, which undergoes [2 + 2]-photocycloaddition affording a single cyclobutane isomer.

Six copper(ii) chloride complexes with crown ethers containing besides oxygen also nitrogen or sulfur atoms in 15- or 18-membered cycle were studied by ESR and electron absorption spectroscopies. Theg and HFI tensor components determined by spectral simulation indicate rhombic symmetry and localization of an unpaired electron on the d xy orbital for all the complexes. The unpaired electron fractions on σ- and π-type metal ion and ligand AO were estimated from ESR and absorption spectra using LCAO MO method. Both σ- and π-type bond covalences were shown to be greater in these complexes compared to only oxygen-containing crown ether complexes. The temperature dependence of g and A components in some complexes may be due to conformational changes.

The synthesis and structure of crown ether styryl dyes representing a novel class of dyes are considered. Data on photoisomerization and photo-induced 1, 2-cycloaddition with formation of cyclo-butane derivatives are briefly analyzed.