Protonation of 2-quinolylthiazoles in the ground and excited states in ethanol

The protonation of some 2-quinolylthiazoles by trichloroacetic, trifluoroacetic, and sulfuric acids in the ground and excited states was studied in ethanol. The formation of the cations was found in the reaction with sulfuric acid. The formation of a mixture of cations and ionic pairs was found in the reactions with trichloroacetic and trifluoroacetic acids. The spectral-luminescence parameters of the reaction products obtained and the kinetic characteristics of the processes were determined.     

Photochemical production of non-equilibrium conformer concentrations in glassy solutions of diarylethylenes at 77 K

Absorption and fluorescence spectra of glassy solutions of some trans-stilbene-like molecules were found to differ remarkably provided trans-diarylethylenes were obtained photochemically at 77 K in situ. The phenomenon has been rationalized as being due to the production of non-equilibrium concentrations of conformers (rotamers) in view of the restrictions imposed by the solid matrix.     

Experimental and theoretical investigation of the spectral and luminescent properties of some acridine compounds

Complex (experimental and quantum-chemical) investigation of the spectral and luminescent properties of acridine, 9-aminoacridine, 2,7-dimethyl-9-ditolylaminoacridine, and their protonated forms was performed. The electronic absorption and fluorescence spectra of the acridine dyes were studied at room temperature in ethanolic solutions at different pH values and in other solvents of different chemical nature and polarity. The energies of the excited states, the deactivation rate constants for the excited states, and the dipole moments are presented, which were obtained by calculations using the method of intermediate neglect of the differential overlap with special spectroscopic parameterization.     

Complex formation of 2,2-diphenyl-2H-benzo[f]chromene containing the aza-18-crown-6-ether fragment in the polymeric layer

The synthesis of 2,2-diphenyl-2H-benzo[f]chromene containing the aza-18-crown-6-ether fragment was described. Its complex formation with alkaline-earth metal ions in dibutyl phthalate and the polymeric gelatin film was investigated. The treatment of the layers containing the ionophore mentioned with aqueous solutions of the corresponding salts in the presence of NaBPh₄ as the phase transfer catalyst results in the extraction of the metal cation into the polymeric layer due to complex formation with crown-containing benzo[f]chromene. The complex formation is accompanied by changes in the spectroscopic characteristics of chromene in the closed and open forms and an increase in the lifetime of the merocyanine form. The effects obtained depend on the metal cation concentration in a solution and the time of layer treatment.     

Computer simulation of band shapes in electronic absorption spectra of dimers of organic dyes

The band shapes in the absorption spectra of dimers of cyanine dyes were simulated using a combination of an empirical molecular force field for the ground state with quantum-chemical calculations of the electron excitation energy as a function of normal nuclear coordinates. The shape and the width of an absorption band strongly depend on the mutual arrangement of the monomers. If the monomers are located one directly above the other, the sublevels arising from intramolecular vibrations disappear in the spectrum, and a large hypsochromic shift of the 0-0-transition band is observed, which results mainly from through-space interaction of monomer orbitals. If the monomers are strongly shifted relative to each other, the sublevels mentioned are also absent in the spectrum, but the bathochromic shift of the 0-0-transition band is small and results from interaction of dipole moments of electron transitions. A rather broad region of intermediate structures is found between these dimer forms, where the interaction of dipole moments of electron transitions in monomers is low, and the shapes of absorption bands are similar to those of the monomers.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1705–1710, September, 1995.This work was financially supported by the Russian Foundation for Basic Research (Project No. 94-03-08539) and the International Science Foundation (Grant M1Z 000).     

Crown-ether styryl dyes

The surface enhanced Raman scattering (SERS) spectra of styryl dyes containing a crown-ether group and a heteroaromatic residue with sulfoalkyl (1a) or alkyl (1b)N-substituent and of their complexes with Mg²⁺ cations were recorded in the 10^–4–10^–8 mol L^–1 concentration range. A model for the interaction of compoundsla,b with a silver surface during their adsorption on an electrochemically treated electrode was suggested. Fastcis-trans relaxation of the adsorbed molecules1a,b and complexes (1a,b)Mg²⁺ was found. It was shown that at [1a] = 10^–5 mol L^–1 and moderate molar ratios (C _Mg/[1a] = 3/1 to 9/1) in acetonitrile solutions, (trans-1a)Mg²⁺ complexes are joined into head-to-tail type dimers. An excess of Mg²⁺ cations (C_Mg/[1a] > 100) leads to dissociation of the dimers yielding (trans-1a)(Mg²⁺)₂ complexes. The formation of dimers from complexes (trans-1a)Mg²⁺ is accompanied by a substantial distortion of the planar structure oftrans-1a. This may be an important factor influencing the efficiency of photocycloaddition involving dimers of (trans-1a)Mg²⁺.For part 15, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2429–2436, December, 1995.The work was carried out with financial support of the Russian Foundation for Basic Research (Project No. 94-03-08760) and, to some extent, of INTAS (Grant No. 93-1829) and of the International Science Foundation (Grant No. MHAOOO).     

Photoisomerization of diarylethylenes

Conclusions The absolute quantum yields of fluorescence and cis trans photoisomerization for naphthylethylenes in liquid and solid solutions at room temperature were measured by the methods of fluorescence and spectrophotometry.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 298–306, February, 1975.