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Isomerization, photo-induced

DAE-based compounds have attracted great attention because of their unique characteristic, consisting of a reversible photo-induced isomerization under irradiation at two different wavelengths (see Fig. 13 and a detailed discussion in Sect. 4.2.1). [Pg.95]

Atmospheric oxygen may initiate in situ polymerization [55] as well as hght as exemplified by the photo-induced isomerization/polymerization of (Z,Z)-muconate anions in the gallery space of LizAl LDH [61] and the photoisomerization of indolinespirobenzopyran [62]. [Pg.135]

The main drawback of the trans complexes discussed earlier is their thermal and photo-induced isomerization back to the cis configuration. In an effort to stabilize... [Pg.317]

Using the above definition, the process of a photo-induced isomerization involves an excitation followed by a deexcitation involving a rearrangement. Rearrangement and dissociation were two of the few possibilities for deexcitation known during the 1920-30 s. [Pg.5]

Allosteric control of a ligand-gated ion channel75 and light-controlled expulsion of molecules from mesostructured silica nanoparticles,76 both based on the photo-induced isomerization of azobenzene, have also been reported. [Pg.510]

Acetylene is one of the simplest hydrocarbons and a fundamentally important chemical in organic chemistry. The electronic structure of acetylene and its related compounds have been extensively studied both experimentally and theoretically, and a number of interesting observations have been reported. For example, a trans-bent structure has been reported for acetylene in an excited state [42, 43] and also in a radical anion form [34, 44]. The interaction between acetylene and metal atoms such as A1 and Li has been studied by inert gas matrix isolation (MI) ESR and IR methods [45-48]. Here we present our ESR study on the structural distortion in acetylene radical anion in the glassy 2-MTHE matrix, which is another example showing a mixing of the k and higher-lying a orbitals at the C=C carbons similar to that at the C=C carbons for the perfluoroalkene radical anions. In addition photo-induced isomerization reaction of the acetylene radical anion in the matrix is briefly presented. [Pg.224]

In the biochemistry of vision (see Chapter 17), the interaction of rhodopsin, a GCPR, with light results in the photo-induced isomerization of cis retinal imine to trans retinal imine. This causes conformational changes in rhodopsin, which ultimately result in the closing of an ion channel, polarization of the cell membrame, and a nerve impulse that is transmitted to the brain in vision. [Pg.1165]

The helical sense of polyisocyanates 147 and 148 can be controlled in terms of photo-induced isomerization of the side-chain chromophores. For 147, photoirradiation causes cis-trans isomerization of the azo moiety, which induces a change in the helix population of the main chain. In the case of 148 having a chiral bicyclo[3.2.1] octan-3-one group in the side chain, photoirradiation results in rotation around the styryl double bond in the side chain.When (+)- or (-)-circularly polarized light (CPL) is used for irradiation, the chirality of the bicyclo... [Pg.657]

The phase transitions starting from the smectic phase were also observed in several doped systems [57-60]. The smectic LC host 8CB, doped with chiral molecules and azobenzene compounds, showed the phase transition from smectic to cholesteric due to the photo-induced isomerization of azobenzene molecules, and the prolonged irradiation drove the phase transition further to the isotropic phase. Matsui et al. also reported a chiral smectic C (SmC )-cholesteric (N ) phase sequence in azo-dye-doped ferroelectric LCs [57]. [Pg.154]

Many experimental results have suggested that the conformational modification of the polythiophene backbone can be induced through order-disorder transitions of the side-chains [59]. It was then postulated that various external stimuli could pertuib the side-chain organization and consequently induce some chromic effects. These side-chain transitions can be induced by heating (thermochromism), varying the solvent quality (solvatochromism), ion complexation (ionochromism), photo-induced isomerization (photochromism) and affinity binding (affinity or biochromism) giving rise to a novel class of field responsive materials. [Pg.116]

Among cycloalkenes, cyclohexenes, cycloheptenes, and cyclooctenes and their 1-methyl derivatives imdergo ci -tram-isomerization on irradiation. Trans-isomers of cyclohexenes and cycloheptenes are veiy unstable because of high ring strain and hence are isolated by trapping in hydroxyhc solvents like methanol [4]. For example, the photo-induced isomerization of cis-l-methylcyclohexene 2 to transisomer is trapped in methanol as methanol adduct [4]. [Pg.217]

Douberly GE, Merritt JM, Miller RE. (2005) IR-IR double resonance spectroscopy in helium nanodroplets Photo-induced isomerization. Phys. Chem. Chem. Phys. 7 463-468. [Pg.392]

The examples of photo-induced trans-to-cis isomerization of azobenzene dyes described above are very rare and valuable in supramolecular assembled systems, because the difficulty of the photoisomerization of the azobenzene moiety has been recognized in micellar and monolayer supramolecular systems [86,87]. In addition, other azobenzene-containing organogels, in which the trans-azobenzene moieties are tightly packed in the organogel supramolecular structme, did not show any photo-induced trans-to-cis iso-merizations [59]. Presiunably, in 22b and 44 there is sufficient room for the isomerization aroimd the azobenzene moiety. Thus, photo-induced isomerization is very sensitive to the organogel structure. [Pg.151]

The mechanism (3) is the most simple one. Trans-cis isomerization of organic molecules about an unsaturated linkage is a well known photochromic phenomenon. When we incorporate the trans-cis photoisomer izable chromophores into the backbone of a polymer chain, photo-induced isomerization of the chromophores is expected to induce a conformational change of the polymer chain. Table I summarizes polymers having photoisomerizable unsaturated linkages in the polymer backbones... [Pg.272]

A wide variety of photo-responsive aromatic polyethers containing azo linkages in the main chain were prepared by nucleophilic aromatic displacement reactions. These polymers undergo cis-trans isomerism in solution when exposed to ultraviolet light. This photo induced isomerization was found to have a profound affect on solution viscosity of the polymers. The polymers were amorphous in nature and undergo crosslinking reactions at elevated temperatures. [Pg.250]

Retinal molecules are the basic element in human eyes that initiates our vision. Malfunctioning of these molecules could lead to eye illness or even blindness. In order to avoid such malfunctioning, one must first understand the so-called photo-induced isomerization in retinal, or conformation change of the molecule upon excitation of light. [Pg.248]


See other pages where Isomerization, photo-induced is mentioned: [Pg.733]    [Pg.289]    [Pg.216]    [Pg.101]    [Pg.336]    [Pg.57]    [Pg.471]    [Pg.217]    [Pg.34]    [Pg.79]    [Pg.167]    [Pg.1836]    [Pg.147]    [Pg.333]    [Pg.147]    [Pg.1098]    [Pg.250]    [Pg.265]   
See also in sourсe #XX -- [ Pg.438 ]




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