Evgeny N. Ushakov

Synthesis, Structure, Spectroscopic Studies, and Complexation of Novel Crown Ether Butadienyl Dyes

Butadienyl dyes of the benzothiazole series with various fragments of benzocrown ethers 1a-c were synthesized for the first time. The structures and spectral properties of crown-containing butadien ...

Synthesis, photochromic behaviour and light-controlled complexation of 3,3-diphenyl-3H-benzo[f]chromenes containing a dimethylamino group or an aza-15-crown-5 ether unit

Synthesis of 3,3-diphenyl-3H-benzo[f]chromenes containing an aza-15-crown-5-ether unit or a dimethylamino group and spectrokinetic study of light-controlled complexation of these compounds with Ca2+ in acetonitrile are reported. The affinity of the azacrown chromene to Ca2+ decreases substantially upon a photoinduced ring-opening reaction. In contrast, dimethylamino chromene, which is unable to bind Ca2+ in the dark, shows a low cation-binding capacity upon UV irradiation. The spectroscopic and kinetic behaviour of the photomerocyanine isomers of these chromenes is strongly affected by complexation with Ca2+. A semi-empirical quantum-chemical study of the merocyanine isomers was applied to interpret the experimental data.

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.

Photosensitive molecular tweezers. 3.* Synthesis and homoditopic complex formation of a bisstyryl dye containing two crown-ether fragments with diammonium salts

A new molecular tweezers, viz., bisstyryl dye containing two 18-crown-6-ether moieties and one p-phenylenedimethylene spacer group, was synthesized. Complex formation of this dye and a model monostyryl dye with ions EtNH3+ and NH3+(CH2)nNH3+ (n = 2−6) in MeCN was studied using spectrophotometry and 1H NMR spectroscopy. The homoditopic bisstyryl dye and diammonium salts form strong supramolecular complexes with pseudocyclic structure.

Prospects of electroanalytical investigations of supramolecular complexes of a bis-crown stilbene with viologen-like compounds bearing two ammonioalkyl groups

Abstract Complexation of the bis-(18-crown-6) stilbene with viologen-like compounds, 1,2-bis{4-[ N -(3-ammoniopropyl)pyridylium]}ethylene, 1,2-bis{4-[ N -(2-ammonioethyl)pyridylium]}ethylene, 1,2-bis{4-[ N -(3-ammoniopropyl)pyridylium]}ethane, and 1,2-bis{3-[ N -(3-ammoniopropyl)pyridylium]}ethylene, bearing two ammonioalkyl groups has been studied in MeCN solutions using cyclic voltammetry and UV–vis spectroscopy. The bis-crown stilbene was found to form strong 1:1 charge-transfer complexes, with the viologen-like diammonium compounds via two-site H-bonding. The complexation results in a considerable positive shift of the first oxidation potential of the electron donor bis-(18-crown-6) stilbene molecule ranging from 160 to 240 mV depending on the nature of the diammonium viologen-like compounds. The magnitude of this shift was used as a measure of the thermodynamic stability of bimolecular complexes between bis-crown stilbene and these viologen-like compounds. The relative contributions of H-bonding and charge-transfer interactions on the complex stability are discussed.

Synthesis, structure, and characterization of chromo(fluoro)ionophores with cation-triggered emission based on N-methylaza-crown-ether styryl dyes.

Novel 2-benzothiazole-, 4-pyridine-, and 2- and 4-quinoline-based styryl dyes containing an N-methylbenzoaza-15(18)-crown-5(6)-ether moiety were synthesized. A detailed electronic spectroscopy study revealed high performance of these compounds as optical molecular sensors for alkali and alkaline-earth metal cations. They were shown to considerably surpass analogous chromoionophores based on N-phenylaza-crown ethers regarding both the ionochromism and the cation-binding ability. In addition, they act as fluorescent sensors for the metal cations by demonstrating cation-triggered emission. Upon complexation with Ba(2+), the fluorescence enhancement factor reaches 61. The structural features of dyes and their metal complexes were studied by NMR spectroscopy and X-ray diffraction. The high degree of macrocycle preorganization was found to be one of the factors determining the high cation-binding ability of the sensor molecules based on N-methylbenzoaza-crown ethers.

Crown-containing styryl dyes: cation-induced self-assembly of multiphotochromic 15-crown-5 ethers into photoswitchable molecular devices

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.

CROWN ETHER STYRYL DYES : 22. SYNTHESIS AND COMPLEXATION OF THE CIS-ISOMERS OF PHOTOCHROMIC AZA-15-CROWN-5 ETHERS

New crown ether-containing styryl dyes of the benzothiazole series containing an aza-15-crown-5-ether moiety were synthesized. Thetrans-cis-photoisomerization of these dyes and their analogs was studied; the effect of metal cations on the kinetics of darkcis-trans-isomerization was elucidated. The stability constants of the complexes of thecis-isomers of these dyes with Ca(ClO4)2 were estimated. The dramatic increase (by more than three orders of magnitude) in the stability of the complexes on passing from a cationic dye to a betaine was attributed to the formation of an intramolecular bond in thecis-complexes between the sulfo group of theN-substituent and the metal cation located in the cavity of the azacrown-ether moiety.

Photochromic crown ether complexes: A Raman spectroscopic study

Abstract Resonance and preresonance Raman spectra have been obtained in the region 400–1700 cm −1 for some benzothiazolium and indolinium steryl dyes containing a crown ether ring. Spectra arising from the trans isomers are observed selectively due to the resonance effect, and the principal features can be attributed to modes of the central conjugated PhN + CCCPh unit present in each of these molecules. Complex formation between the dye molecules and Mg 2+ in acetonitrile solution results in intramolecular electron transfer. This is observed in the Raman spectra as a downshift of a band assigned to PhO vibration in the crown ether unit, and upshifts of several bands associated with the PhN + CCCPh unit, including the phenyl ring, CC and + NC stretches. The results demonstrate the sensitivity of the Raman spectra to changes in the structure and bonding within these photochromic complexing agents on binding to metal ions, and indicate that they may serve as a useful probe for the complicated photoisomerization and complexation reactions of these interesting systems.

Matrix Isolation, Zero-Field Splitting Parameters, and Photoreactions of Septet 2,4,6-Trinitrenopyrimidines

The key intermediates of decomposition of high-energy 2,4,6-triazidopyrimidine and its 5-chloro-substituted derivative, the detonation of which is used for preparation of carbon nitrides, were investigated using electron paramagnetic resonance (EPR) spectroscopy in combination with quantum chemical calculations. The decomposition of the triazides was carried out photochemically, using the matrix isolation technique. The photodecomposition of both triazides with 254 nm light in argon matrices at 5 K occurred selectively to subsequently give the corresponding triplet 4,6-diazido-2-nitrenopyrimidines, quintet 4-azido-2,6-dinitrenopyrimidines, and septet 2,4,6-trinitrenopyrimidines. The latter were photochemically unstable and decomposed to form triplet nitrenes NCN and NNC as well as triplet carbenes NCCCN, HCCN, and HCCCCN. The results obtained provide important information about exchange interactions in high-spin nitrenes with the pyrimidine ring and the mechanism of the formation of carbon nitrides during thermolysis of 2,4,6-triazidopyrimidine.