O. A. Fedorova

Effect of metal cations on the photochromic properties of spironaphthoxazines conjugated with aza-15(18)-crown-5(6) ethers

Spironaphthoxazines conjugated with aza-15(18)-crown-5(6)-ether moieties at the 6′-position of the naphthalene fragment (Crown-containing Spironaphthoxazines, CSN) were synthesised and studied for the first time. The addition of Li+ and alkaline earth (Mg2+, Ca2+, Sr2+ and Ba2+) metal cations to CSN solutions results in a hypsochromic shift of the UV absorption band of the spiro form and a bathochromic shift of the absorption band of the merocyanine form in the visible region. In addition, the equilibrium shifts to the merocyanine form, and the lifetime of the photoinduced merocyanine form increases. Analysis of the spectral and kinetic data allows a complexation scheme to be proposed and the stability constants of the resulting complexes to be calculated. According to the results obtained, the complexation with Li+ and alkaline earth nmetal cations in acetonitrile initially involves the crown ether moiety; the participation of the merocyanine oxygen atom in the complexation process occurs at a high metal cation concentration. The UV-induced isomerisation of CSN into the merocyanine form causes a decrease of the cation binding ability.

Crown-containing styryl dyes

Complexation of styryl dyes containing theN-phenylaza-15-crown-5 fragment (trans-2a,b) with Ca2+ ions in MeCN was studied. Unlike cationic dyetrans-2a, betainetrans-2b forms both complexes of 1∶1 stoichiometry and aggregates consisting of four dye molecules and one Ca2+ ion. Cation-induced aggregation was observed also for the analog of dyetrans-2b, which contains a dimethylamino group instead of an azacrown ether fragment (trans-3). Apparently, the interaction between a metal cation and sulfo groups of moleculestrans-2b ortrans-3 makes the main contribution to the stability of aggregates. The dependence of the stability of aggregates on the nature of the metal cation was studied.

CROWN-CONTAINING STYRYL DYES. XIV: SYNTHESIS, LUMINESCENCE, AND COMPLEXATION OF THE TRANS-ISOMERS OF CHROMOGENIC 15-CROWN-5-ETHERS

Novel crown ether styryl dyes containing heterocyclic residues with various substituents were synthesized. The fluorescence and absorption spectra of thetrans-isomers of crown ether styryl dyes and their complexes with metal cations were studied. Based on spectral data, the influence of the nature of a heterocyclic residue, the crown ether fragment, and the temperature on the fluorescence of dyes and their complexes with metal cations was elucidated.

Photochromic Ionophores: Synthesis, Photoinduced Isomerization and Cycloaddition of Crown Ether Styryl Dyes

Abstract 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.

A surface-enhanced Raman spectroscopic study of novel photochromic benzodithiacrown ether styryl dyes

Abstract Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) spectra of two benzothiazolium styryl dyes containing a crown ether ring with sulfur and oxygen heteroatoms have been obtained at low concentration (10 −5 –10 −7 M) in the presence of silver colloids. A preliminary assignment of the observed bands to particular vibrational modes has been made by comparison of infrared (IR), normal Raman (R) and SERS data obtained from thiacrown ether and benzothiazolium molecular fragments with SERRS spectra of a benzothiazolium styryl dye containing a normal crown ether ring and with assignments reported previously for related molecules. The results indicate that the sulfur atoms of both the benzothiazolium and the dithiacrown ether groups participate in adsorption at the silver surface; possible models of adsorption of these dyes and their fragments are discussed.

SYNTHESIS OF FORMYL DERIVATIVES OF BENZOCROWN ETHERS CONTAINING N, S, AND O HETEROATOMS IN THE MACROCYCLE

A method for the synthesis of 4′-bromobenzodithia-15(18)-crown-5(6) and 4′-bromobenzodiaza-15 (18)-crown-5(6) by condensation of 3,4-di(2′-haloethoxy)bromobenzene with polyoxaalkanes containing terminal SH or NHMe groups was suggested. The method for the synthesis of formyl derivatives of benzocrowns containing N, S, and O heteroatoms in the macrocycle based on the metallation of appropriate bromo derivatives with BunLi followed by treatment of the resulting organolithium intermediates with DMF was developed. Oximes and semicarbazones of benzaldehydes containing a crown ether fragment were obtained, and their transformation into the original aldehydes by treatment with KNO2 in an acid medium was studied.

Excited state relaxation processes of crowned styryl dyes and their metal complexes

The fluorescence of novel crowned styryl dyes and their complexes with sodium cation was studied. The fluorescence quantum yield of crowned styryl dye is higher than that of non-crowned ones. While absorption and fluorescence spectra of a styryl dye are shifted to high frequency regions, its fluorescence quantum yield in the absence of photoisomerization is practically unchanged, and the rate constant of its temperature fluorescence qienching rises as it forms a complex with the metal ion. The relaxation processes of photoisomerization and recoordination are considered. The adiabatic change of metal ion coordination in crown cycle may proceed in the excited state. Thetrans-cis photoisomerization of styryl dyes and their metal complexes is a barrierless reaction.

Crown-containing spironaphthoxazines and spiropyrans. 3. Synthesis and investigation of the merocyanine form of crown-containing spirobenzothiazolinonaphthoxazine

A method for the synthesis of the spirobenzothiazolinonaphthoxazine, stable in the merocyanine form and containing a crown-ether fragment was developed. The complexing properties of the prepared merocyanine compound and the spectroscopic and photochromic characteristics of its complexes with alkaline earth metal cations were studied by NMR and UV spectroscopy. The results were analyzed using quantum-chemical calculations. The addition of alkaline earth metal perchlorates to a solution of a crown ether-containing merocyanine dye in MeCN results in the coordination of metal cations to two binding centers, namely, the crown-ether fragment and the merocyanine oxygen atom. This gives rise to two types of complexes, which differ substantially in their structurally. The complexation induces changes in the UV spectra and influences on the photochromic behavior of the prepared compound.

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.

Macrocycle opening in formyl derivatives of benzocrown ethers under the action of methylamine

A new method for synthesizing nitrogen-containing podands by nucleophilic regioselective cleavage of the macrocycle in formyl derivatives of benzocrown ethers by heating with methylamine and methylammonium chloride has been developed. This reaction is the first example of crown ether opening by a nitrogen-containing nucleophile.