A Raman spectroscopic study of photochromic benzothiazolium dyes
摘要:
Resonance Raman spectra using several excitation wavelengths have been obtained in the region 300-1750 cm-1 for two photochromic benzothiazolium dyes containing a crown ether ring. Bands arising from both cis- and trans-isomers have been distinguished by comparing the spectra observed at different resonances and under different sample conditions. Preliminary assignments of the bands have been made, allowing insight into the changes in structure and bonding which occur on photoisomerization.
Accumulation of the photonic energy of the deep-red part of the terrestrial sun irradiation by rare-earth metal-free <i>E</i>–<i>Z</i> photoisomerization
Here, drastic shortening of the syntheticroute of crown ether functionalized hemicyanine dyes, suitable for efficient E–Z photoisomerization under extremely low excitation light intensities compared with unconcentrated sunlight is reported. The higher energetic form was successfully stabilized by rare earth free cations – in this case by styryl dye-Ba2+ complexes. For the first time E–Z photoisomerization
Precious metal-free molecular machines for solar thermal energy storage
作者:Meglena I Kandinska、Snejana M Kitova、Vladimira S Videva、Stanimir S Stoyanov、Stanislava B Yordanova、Stanislav B Baluschev、Silvia E Angelova、Aleksey A Vasilev
DOI:10.3762/bjoc.15.106
日期:——
and elemental analysis. The steady-state photophysical properties of the dyes were elucidated. The stability constants of metal complexes were determined and are in good agreement with the literature data for reference dyes. The temporal evolution of trans-to-cis isomerization was observed in a real-time regime. The dyes demonstrated a low intrinsic fluorescence of their Ba2+ complexes and high yield
A Cation-Specific, Light-Controlled Transient Chromoionophore Based on a Benzothiazolium Styryl Azacrown Ether Dye
作者:Igor K. Lednev、Ronald E. Hester、John N. Moore
DOI:10.1021/ja964154j
日期:1997.4.1
A benzothiazolium styryl azacrown ether dye (1) and its complexation with Ba2+ and Na+ cations in acetonitrile solution have been studied by UV-vis absorption and emission spectroscopy, trans-1 is found to act as a normal chromoionophore for Ba2+ and Na+ at high concentration (greater than or equal to 10(-2) M) by complexation with the azacrown and as a light-controlled, transient chromoionophore specific for Ba2+ at low concentration (10(-5)-10(-3) M). A quantitative analysis of the complexation and thermal reactions following photolysis has enabled a detailed mechanism to be proposed: trans-1 photoisomerization produces cis-1, which is stabilized in the presence of Ba2+ by dual intramolecular complexation of the cation with both azacrown and sulfonate groups.
Direct Observation of Photocontrolled Ion Release: A Nanosecond Time-Resolved Spectroscopic Study of a Benzothiazolium Styryl Azacrown Ether Dye Complexed with Barium
作者:Igor K. Lednev、Ronald E. Hester、John N. Moore
DOI:10.1021/jp972360n
日期:1997.10.1
A benzothiazolium styryl azacrown ether dye (1) and its photocontrolled complexation with Ba2+ in acetonitrile solution have been studied by nanosecond time-resolved UV-visible absorption spectroscopy. Continuous visible irradiation of trans-1 in the presence of Ba2+ was used to generate a photostationary-state mixture with ''closed'' cis-1-Ba2+ present in high concentration: in this form, the barium cation is complexed with both the azacrown and a propylsulfonate group pendant to the benzothiazolium dye. A nanosecond UV photolysis pulse was used to induce photoisomerization of this ''closed'' cis-1-Ba2+ species. Time-resolved UV-visible absorption studies have revealed that the barium cation initially remains complexed to the azacrown in the trans-isomer formed <50 ns after UV photolysis and that the cation is subsequently released from the azacrown on a time scale of ca. 700 ns, consistent with the equilibrium composition of the solution expected from the thermal chemistry under these conditions. Along with time-resolved and steady-state studies of the effect of temperature and cation concentration, these studies have enabled a quantitative mechanism to be proposed for the thermal and photochemical ion-complexing properties of this dye. These direct observations demonstrate that sustained, photocontrolled ion release from an azacrown ether dye can be achieved within 1 mu s of photolysis.