80631-72-7Relevant articles and documents
Supercritical Carbon Dioxide. The Cis to Trans Relaxation and ?,?* Transition of 4-(Diethylamino)-4'-nitroazobenzene
Sigman, Michael E.,Leffler, John E.
, p. 3123 - 3126 (1987)
Rates of the cis-trans isomerization of 4-(diethylamino)-4'-nitroazobenzene (DENAB) have been determined for supercritical CO2 media at 32.4 deg C and several densities and DENAB concentrations.A plot of ΔG (excit.) against the Kamlet-Taft ?* parameter has two linear parts, one for the CO2 media and alkanes and another for more polar solvents.The slope for the CO2 and alkanes is positive and small, and that for the other solvents is large and negative.It is suggested that the reaction mechanism in the CO2 media and in alkanes is inversion at one of the azo nitrogens, while in the more polar solvents it is rotation about the bond between the azo nitrogens, for which the transition state is much more polar.The point of intersection of the two lines is at a ?* value of about +0.2.Unlike the ΔG (excit.) values, the Emax of the ?,?* internal charge-transfer band of DENAB are adequately accommodated by a single line
Effect of head group size on the photoswitching applications of azobenzene Disperse Red 1 analogues
Goulet-Hanssens, Alexis,Corkery, T. Christopher,Priimagi, Arri,Barrett, Christopher J.
supporting information, p. 7505 - 7512 (2014/11/08)
We investigate the effect of the increased molecular bulk in the 'head' group for a class of newly synthesized azobenzene chromophores with a clickable ethynyl group para and a nitro group ortho to the azo bond on the distal benzene ring. This 'variable-head' functionalization provides a family of dyes with photophysical characteristics very similar to those of Disperse Red 1, one of the most commonly used azo dyes in materials science. Phenyl, naphthyl, and anthracyl derivatives were synthesized as small molecules, monomers, homopolymers, and copolymers in a rapid and facile manner using click chemistry, confirming the versatility of this parent chromophore. Photochemical and spectral studies indicate that this strategy is suitable to build a 'bulkiness series' of stimuli-responsive materials, as the various material derivatives retain the absorption and kinetic characteristics of the parent chromophore necessary for all optical patterning applications that DR1 dyes have been optimized for. In thin films, larger head group size was found to increase the stability of light-induced birefringence in copolymers. The homopolymers formed stable surface-relief gratings upon interference irradiation, whose grating depths correlate with head group size, demonstrating that this new class of polymers can also undergo tailored macroscopic photoinduced motions, which could have applications in all optical nano-patterning. the Partner Organisations 2014.
Rate constants of the thermal cis-trans isomerization of azobenzene dyes in solvents, acetone/water mixtures, and in microheterogeneous surfactant solutions
Gille, Kathrin,Knoll, Helmut,Quitzsch, Konrad
, p. 337 - 350 (2007/10/03)
Rate constants kiso of the thermal cis-trans isomerization of four 4,4′-nitro-aminoazobenzenes with different amino groups have been determined in homogeneous aprotic solvents and polyglykol oligomers, primarily by means of conventional flash photolysis. The rate constants have been correlated with polarity (according to λmax from UV/Vis absorption spectra of the trans isomers) and bulk viscosity of the solvents. Qualitative conclusions about the influence of varying concentrations of water with respect to polarity and hydrogen bonding on kiso- and λmax-values in acetone/water mixtures were derived. Based on these results the data from microheterogeneous solutions have been interpreted. In microheterogeneous water/surfactant solutions kiso-values of selected azo dyes were strongly dependent on the concentrations of SDS, Triton X-100, C12EO8 in water, and varied with the composition of bicontinuous microemulsions of Igepal CA-520/heptane/water. The large spread of isomerization rate constants is in part due to varying microviscosity. Replacement of H2O by D2O in aqueous surfactant solutions produced surprisingly large kinetic solvent isotope effects.
Solvent-Induced Mechanism Change in Charge-Transfer Molecules. Inversion versus Rotation Paths for the Z -> E Isomerization of Donor-Acceptor Substituted Azobenzenes
Shin, Dong-Myung,Whitten, David G.
, p. 5206 - 5208 (2007/10/02)
-
