54515-64-9Relevant academic research and scientific papers
Phototransformation of stilbene in van der Waals nanocapsules
Ananchenko, Gennady S.,Udachin, Konstantin A.,Ripmeester, John A.,Perrier, Thomas,Coleman, Anthony W.
, p. 2441 - 2447 (2008/02/08)
We have utilized para-hexanoylcalix[4]arene nanocapsulcs as hosts to carry out phototransformations of cis- and trans-stilbene. Single-crystal X-ray diffraction studies were performed to define precisely the location of encapsulated stilbenes inside the capsule and to analyze possible pathways of pholotransformation. cis-Stilbene stacks as a π-π dimer located at the center of the capsule, whereas trans-stilbene does not form such a dimer. Irradiation of the crystalline inclusion complexes of each isomer of stilbene in the solid state leads to the appearance of the second isomer, and after prolonged photolysis, photodimerization also occurs. syn-Tetraphenylcyclobutane is formed as the major product of dimerization and its yield depends on the time and intensity of irradiation. In most cases, the single crystals of the complexes remain intact during irradiation; hence, the nanocapsules have the potential to serve as robust nanoreactors in the solid state. The confinement in the nanocapsules is sufficient to keep the reacting molecules together, although this is less restrictive than for trans-stilbene crystals, in which the molecules cannot achieve a favorable orientation for dimerization.
Accelerated Photodimerization of Stilbenes in Methanol and Water
Ito, Yoshikatsu,Kajita, Toru,Kunimoto, Kazuhiko,Matsuura, Teruo
, p. 587 - 591 (2007/10/02)
Photodimerization of stilbenes 1a-f, especially that of 4- and 3-acetylstilbenes (1c and 1d, respectively), is more efficient when a hydroxylic solvent (methanol or water) is employed as the reaction medium than when a nonhydroxylic solvent (hexane, benzene, or acetonitrile) is employed.The stilbenes 1a-f are more strongly fluorescent in methanol than in benzene.It is proposed that this accelerated photodimerization in the hydroxylic solvent originates from formation of a fluorescent solute-solute aggregate.
Azastilbenes. 2. Photodimerization
Vansant, J.,Toppet, S.,Smets, G.,Declercq, J. P.,Germain, G.,Meerssche, M. Van
, p. 1565 - 1573 (2007/10/02)
The photochemical behavior of several azastilbenes has been followed in concentrated solution and in the solid state.In acetonitrile and benzene isomerization and dimerization occur, the reactions being generally faster in acetonitrile.In methanol, however, photoreduction as well as photoaddition of the solvent intervene and are important processes.With irradiation in the solid state, dimerization occurs only for some azastilbenes and their quaternary salts, depending on the orientations of the molecules within the crystal lattice and the distances between adjacent double bonds (3.5-4.2 Angstroem).X-ray analysis has shown that trans-1,2-di(2-pyrazinyl)ethylene crystallizes in two distinct modifications of which only one has a crystal stacking suitable for topochemical dimer formation.The dimers were characterized by 1H and 13C NMR, IR, and mass spectroscopy.The crystalline and molecular structures of five of them were determined by X-ray diffraction, namely cyclobutane dimers of 1,2-di(4-pyridyl)ethylene, 1,2-di(2-pyridyl)ethylene, 1,2-di(2-pyrazinyl)ethylene (all three r-ctt dimers), and 1-(3-pyridyl)-2-(2-pyrazinyl)ethylene (r-ctt head-to-head and head-to-tail dimers).
