77251-17-3Relevant academic research and scientific papers
The Thermal Cis-to-trans Isomerization of N,N'-Diacylindigos. Kinetic Pressure, Solvent, and Substituent Effects.
Sueishi, Yoshimi,Ohtani, Kazuo,Nishimura, Norio
, p. 810 - 814 (1985)
The kinetics of the thermal cis-to-trans isomerization of N,N'-diacylindigos(DAI) in various solvents and under high pressures has been studied.N,N'-Dibenzoylindigos(DBI) isomerize about 10 times slower than molecules not having a benzene ring in the acyl groups.The values of the activation volumes were about 8.0 cm3 mol-1 for the former and about 3.0 cm3 mol-1 for the latter.It was suggested that the thermal isomerization proceeds via the biradical mechanism.The positive values of the activation volume have been interpreted in terms of the increase in theintrinsic volume upon activation.The differences in the isomerization rates and the activation parameters between DBI and the others have been ascribed to an additional interaction between the two phenyl rings in the acyl groups in the cis-ground state.
Trans to cis photoisomerization of N,N'-disubstituted indigo dyes via excited singlet states; a laser flash photolysis and steady state irradiation study
Goerner, Helmut,Pouliquen, Joseph,Kossanyi, Jean
, p. 708 - 717 (2007/10/02)
The relaxation pathways of excited trans-N,N'-diacylindigo dyes (trans-1-trans-4) and of the rigid trans (5) and cis (6) indigo analogues have been studied by nanosecond flash photolysis and steady state measurements.In fluid solution the trans to cis photoisomerization of 1-4 occurs via a singlet excited state mechanism on direct excitation, and the triplet state appears to be reached only by sensitized reaction.The lower quantum yield for trans --> cis isomerization of 2-4 at room temperature, as compared to 1, is due to a thermally activated internal conversion step leading to the trans ground state.This pathway competes with fluorescence and twisting of the molecule around the central double bond in the excited singlet state.Increasing the viscosity of the medium decreases the twisting of the flexible molecules and, as a consequence, increases the population of the lowest triplet state.A triplet transient, the intensity of which increases with the viscosity of the medium, could be characterised at low temperature under direct excitation.A transient species, which can be assigned to a triplet state on the basis of quenching experiments and on the fact that the same transient could be found under sensitized conditions, also has been observed at room temperature for the rigid 5 and 6 molecules.Quenching measurements of triplet sensitizers by 5, trans-1, and trans-2 enables the localization of the triplet energy at around 40 kcal/mol.
Photoisomerization of N,N'-disubstituted indigos. A search for energy storage
Pouliquen, Joseph,Wintgens, Veronique,Toscano, Vicente,Jaafar, Brahim Ben,Tripathi, Sadhana,et al.
, p. 2478 - 2486 (2007/10/02)
The photochemical behaviour of N,N'-disubstituted indigo dyes has been investigated.The trans to cis and cis to trans photoisomerization quantum yields are found to be of the order of 0.25 or less (down to 0.03).These dyes, which fluoresce only weakly in solution and at room temperature, show a drastic increase in their fluorescence when inserted into a polymer matrix or at 77 K in butyronitrile glass.This has been interpreted in terms of the inhibition of formation of a twisted excited intermediate as well as of the rotation of the substituent on the nitrogen atom.An important electron transfer occurs from the singlet excited state when the indigo dyes are placed in the presence of electron-donating molecules.When irradiating with visible light, the photostationary state is always in favour of the trans isomers.This, and kinetic as well as thermodynamic considerations, excludes these compounds as candidates for solar energy storage.
