Novel asymmetric dihetarylethenes derived from N-isopropylindole and thiophene: synthesis and photochromic properties

Novel asymmetric dihetarylethenes, viz., 3-(1-isopropyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)furan-2,5-dione and 1-alkyl/aryl-3-(1-isopropyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)-1H-pyrrole-2,5-diones, were obtained. These dihetarylethenes exhibit photochromism in solutions. Replacement of the N-methyl group in the indole fragment by the N-isopropyl group imparts photochromic properties to the resulting furan-2,5-dione derivative. The open forms of (N-isopropylindol-3-yl)pyrrole-2,5-diones are characterized by lower quantum yields of fluorescence, and their cyclic forms are thermally more stable.     

Synthesis,crystal structure,and electroluminescent properties of zinc and cadmium tetradentate azomethine complexes

Chemical and electrochemical syntheses of zinc(II) and cadmium(II) complexes based on tetradentate Schiff bases (H₂L¹ and H₂L²) resulting from condensation of 2-tosylaminobenzaldehyde with 3,6-dioxa-1,8-octanediamine or 4,9-dioxa-1,12-dodecanediamine were performed. The structure, composition, and properties of the complexes were studied by elemental analysis, IR, ¹H NMR, and UV spectroscopy, X-ray absorption spectroscopy, and X-ray diffraction. The zinc(II) and cadmium(II) complexes luminesce in a DMF solution in the blue spectral region (λ_PL = 425–433 nm), the photoluminescence quantum yield φ being 0.25–0.30. Multilayer zinc(II)- and cadmium(II)-based electroluminescent structures with green-blue emission of the exciplex nature were fabricated.     

Zinc complexes of 1-Propyl-2-(2-tosylaminophenyl)-5-aminobenzimidazole: Synthesis,structure, and luminescence properties

1-Alkyl-2-(2-tosylaminophenyl)-5-aminobenzimidazole and related zinc complexes are synthesized. The structure of the complex with zinc pivalate is determined by X-ray diffraction analysis. The fluorescence with the anomalous Stokes shift of the benzimidazole ligand system in solution is transformed into the fluorescence with the normal Stokes shift upon complex formation due to blocking the mechanism of intramolecular proton transfer in the excited state or upon the transition to the crystalline state formed by zwitterionic forms that are generated due to the proton transfer from the sulfonamide group to the amino group.     

Photoinitiated Processes in Molecules of Schiff Bases Having an NH···N Intramolecular Hydrogen Bond

Study of the absorption and luminescence spectra of Schiff bases derived from o-(p-tolylsulfonylamino)benzaldehyde has shown that these systems, like those derived from salicylaldehyde, are characterized by intramolecular proton transfer in the excited and ground electronic states. This process is responsible for the appearance at 77 K of fluorescence with an anomalous Stokes shift and formation of ketone structures. Unlike o-[alkyl(or aryl)iminomethyl]phenols, o-[alkyl(or aryl)iminomethyl]anilines do not give rise to acoplanarization of the ketone fragment, which could follow intramolecular proton transfer in the excited state and is responsible for fluorescence with an anomalous Stokes shift and formation of colored structures.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Photodynamic chromogenic system based on photo- and ionochromic 8-(1,3-benzoxazol-2-yl)-substituted spirobenzopyran

8-(1,3-Benzoxazol-2-yl)-substituted spirobenzopyran is a new chromogenic system in which complexation with metal ions accompanied by a change in color can be controlled by photoirradiation. According to X-ray crystallography, the merocyanine ligand in the zinc complex has the TTT conformation.     

Synthesis and studies of new photochromic spiropyrans containing a formylcoumarin fragment

A computer search for new photoactive compounds among indoline spiropyrans of coumarin series was carried out using DFT B3LYP/6-31G(d,p) method. Based on the data obtained, the spiropyrans containing a formylcoumarin fragment annulated to the 2H-pyran ring and possessing photochromic properties were synthesized. The structure and photochromism of these compounds were studied by ¹H NMR, IR, and UV/Vis spectroscopy. The introduction of a formyl group into the coumarin moiety of spiropyrans led to a bathochromic shift of the long wavelength absorption maxima of merocyanine isomers, as well as to a considerable increase in their lifetime.     

Synthesis,structure, and photoluminescence properties of <Emphasis Type="Italic">N</Emphasis>-{2-[5-(2-hydroxyphenylmethyleneamino)-1-alkylbenzimidazol-2-yl]phenyl}-4-methylbenzenesulfamides and their zinc complexes

N-{2-[5-(2-Hydroxyphenylmethyleneamino)-1-alkylbenzimidazol-2-yl]phenyl}-4-methyl-benzenesulfamides (H₂L) and their zinc complexes Zn₂L₂ were synthesized. The structure of the ligands and complexes was studied by IR, UV, ¹Н NMR, X-ray absorption spectroscopy, and X-ray diffraction analysis. The complexes show green photoluminescence (λ_fl = 492 nm) with quantum yields φ = 0.07–0.17.     

Spiropyrans and spirooxazines 8. 5��-(1,3-Benzothiazol-2-yl)-substituted spiro[indoline-2,3��-naphthopyrans]: synthesis and spectral and photochromic properties

Novel photochromic 5??-(1,3-benzothiazol-2-yl)-substituted spiro[indoline-2,3??-naphthopyrans] possessing luminescence properties in both the cyclic and merocyanine forms were synthesized. Unlike the 8??-(1,3-benzothiazol-2-yl)-substituted benzopyran analogs, the synthesized compounds are characterized by the lower relative stability of the merocyanine isomers.     

Spiropyrans and spirooxazines 6. The spectral and kinetic properties of 5-(4,5-diphenyl-1,3-oxazol-2-yl)-substituted spironaphthopyrans: an experimental and theoretical study

The spectral and kinetic properties of 5-(4,5-diphenyl-1,3-oxazol-2-yl)spiro[indoline-naphthopyran] derivatives were studied by experimental and theoretical methods. The additional long-wavelength maximum in the absorption spectra of compounds studied is due to the introduction of a diphenyloxazole fragment and corresponds to a π-π* electronic transition with a partial charge transfer character. Substituents have little effect on the kinetic parameters of the spironaphthopyrans studied.