95121-98-5Relevant academic research and scientific papers
Photoisomerization and Fluorescence of Surfactant and Hydrophobic 4- and 4,4'-Substituted Stilbenes in Homogeneous Solution. Observation of Strong Fluorescence Enhancement by Dialkyl Substitution
Brown, Patti Eller,Whitten, David G.
, p. 1217 - 1220 (1985)
Several stilbenes substituted at one (4-) or both (4,4'-) para positions with linear alkyl chains terminating in hydrogen or carboxyl groups have been prepared.These surfactant or hydrophobic stilbenes have been studied primarily in organized assemblies; this paper reports on their behavior in homogeneous (benzene and methylcyclohexane) solution.The behavior of these stilbenes on direct irradiaton is characterized by strong increases (4-5-fold) in both fluorescence and singlet lifetimes for all of the disubstituted or "intrachain" deriatives compared to trans-stilbene; in contrast, relatively little effect is observed for the monosubstituted derivatives.Although the quantum yield for direct trans -> cis isomerization is reduced as a consequence of the enhanced fluorescence, the cis/trans excited singlet decay ratio is unaffected.Studies of the sensitized isomerization indicate that triplets of the substituted stilbenes have similar energies and cis/trans decay ratios to trans-stilbene; however, a somewhat longer triplet lifetime is indicated.The primary changes noted can be accounted for in terms of an enhanced sensitivity of the intrachain stilbenes to viscosity-torsional interactions between solute and solvent.
Nickel-Catalyzed Stereodivergent Synthesis of E- and Z-Alkenes by Hydrogenation of Alkynes
Murugesan, Kathiravan,Bheeter, Charles Beromeo,Linnebank, Pim R.,Spannenberg, Anke,Reek, Joost N. H.,Jagadeesh, Rajenahally V.,Beller, Matthias
, p. 3363 - 3369 (2019/06/28)
A convenient protocol for stereodivergent hydrogenation of alkynes to E- and Z-alkenes by using nickel catalysts was developed. Simple Ni(NO3)2?6 H2O as a catalyst precursor formed active nanoparticles, which were effective for the semihydrogenation of several alkynes with high selectivity for the Z-alkene (Z/E>99:1). Upon addition of specific multidentate ligands (triphos, tetraphos), the resulting molecular catalysts were highly selective for the E-alkene products (E/Z>99:1). Mechanistic studies revealed that the Z-alkene-selective catalyst was heterogeneous whereas the E-alkene-selective catalyst was homogeneous. In the latter case, the alkyne was first hydrogenated to a Z-alkene, which was subsequently isomerized to the E-alkene. This proposal was supported by density functional theory calculations. This synthetic methodology was shown to be generally applicable in >40 examples and scalable to multigram-scale experiments.
Synthesis and characterization of stilbene derivatives for possible incorporation as smart additives in polymers used as packaging films
Day, Gary M.,Howell, Owen T.,Metzler, Michael R.,Woodgate, Paul D.
, p. 425 - 434 (2007/10/03)
Several series of stilbene derivatives for possible use as smart additives in polymers used as packaging films have been prepared and characterized. Differential scanning calorimetry was performed on some of the stilbenes in order to determine any liquid crystal properties. Those compounds which had multiple phase transitions were also shown to have two liquid crystalline phases according to optical microscopy.
Surfactant and Hydrophobic Derivatives of trans-Stilbenes as Probes of Vesicle and Micelle Solubilization Sites. Studies Using Fluorescence and Photoisomerization as Probes
Suddaby, Brian R.,Brown, Patti E.,Russell, John C.,Whitten, David G.
, p. 5609 - 5617 (2007/10/02)
An investigation of the fluorescence and photoisomerization of several surfactant trans-stilbene derivatives in aqueous micelles and vesicles is reported.The temperature dependence of Φf was determined for several media over the range 5-70 deg C.The results present a picture of similar micellar solubilization sites for the trans-stilbene chromophore in every case; the micelle is "seen" by the stilbene as a moderately viscous fluid medium with slightly higher values for Φf and slightly reduced Φt->c compared to nonviscous homogeneous solutions.For vesicles considerably more complex behavior is observed.Generally Φf is considerably higher than in solution and Φt->c is much lower.Several, but not all, of the surfactant and hydrophobic stilbenes show a sharp sensitivity in Φf as a function of T when passing through Tc, the vesicle phase transition temperature.Arrhenius plots for the process competing with fluorescence as a function of temperature show relatively high values for Ea and log A, above Tc, consistent with the high temperature phase providing a microenvironment for the stilbene chromophore like a viscous solvent.Below Tc, the variation of Φf gives much lower values for EA and log A which suggest escape from the fluorescence state is "order limited" rather than viscosity dominated.These results suggest that the low-temperature phase of vesicles presents an environment for the stilbene chromophore more like an inclusion complex than a fluid medium.The effect of cholesterol addition on DODAC vesicles containing the stilbenes is to increase fluidity below Tc and to effectively increase viscosity above Tc.
