Photochromic Compounds with N=N and C=N Chromophores

Fanghänel, D.; Timpe, G.; Orthman, V.

doi:10.1007/978-1-4615-8585-5_3

Cited by 18 publications

(31 citation statements)

References 341 publications

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“…[10][11][12][13][14][15] For a comprehensive review, the reader is referred to the work of Fanghänel et al, 16 and references cited therein. In particular the dependence of the switching kinetics on the type, number, and positioning of substituents has been investigated experimentally.…”

Section: Introductionmentioning

confidence: 99%

Quantum Chemical Investigation of Thermal Cis-to-Trans Isomerization of Azobenzene Derivatives: Substituent Effects, Solvent Effects, and Comparison to Experimental Data

et al. 2009

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Quantum chemical calculations of various azobenzene (AB) derivatives have been carried out with the goal to describe the energetics and kinetics of their thermal cis f trans isomerization. The effects of substituents, in particular their type, number, and positioning, on activation energies have been systematically studied with the ultimate goal to tailor the switching process. Trends observed for mono-and disubstituted species are discussed. A polarizable continuum model is used to study, in an approximate fashion, the cis f trans isomerization of azobenzenes in solution. The nature of the transition state(s) and its dependence on substituents and the environment is discussed. In particular for push-pull azobenzenes, the reaction mechanism is found to change from inversion in nonpolar solvents to rotation in polar solvents. Concerning kinetics, calculations based on the Eyring transition state theory give usually reliable activation energies and enthalpies when compared to experimentally determined values. Also, trends in the resulting rate constants are correct. Other computed properties such as activation entropies and thus preexponential rate factors are in only moderate agreement with experiment.

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Section: Introductionmentioning

confidence: 99%

Quantum Chemical Investigation of Thermal Cis-to-Trans Isomerization of Azobenzene Derivatives: Substituent Effects, Solvent Effects, and Comparison to Experimental Data

et al. 2009

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“…In contrast, for stilbenoid compounds the thermal back reaction is unlikely since the activation barrier (E a ) is on the order of 1.9 eV [1][2][3][4] and thus much higher as compared to azobenzenes (E a ≈ 1 eV; see Figure 1b). [4][5][6][7] Recently, increasing interest has been directed toward research on molecular switches at surfaces due to their potential use in nanotechnology ranging from information storage and processing to adaptive surfaces. 4,[8][9][10] A major goal, relevant to the development of future applications, is to understand and control structural changes of molecular switches, such as azobenzenes and stilbenes adsorbed on solid substrate surfaces.…”

Section: Introductionmentioning

confidence: 99%

Photoisomerization Ability of Molecular Switches Adsorbed on Au(111): Comparison between Azobenzene and Stilbene Derivatives

et al. 2009

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High resolution electron energy loss spectroscopy and two-photon photoemission was employed to derive the adsorption geometry, electronic structure, and the photoisomerization ability of the molecular switch tetratert-butyl-stilbene (TBS) on Au(111). The results are compared with the azobenzene analogue, tetra-tertbutyl-azobenzene (TBA), adsorbed on Au(111). TBS was found to adsorb on Au(111) in a planar (trans) configuration similar to TBA. The energetic positions of several TBS-induced electronic states were determined, and in comparison to TBA, the higher occupied molecular states (e.g., the highest occupied molecular orbital, HOMO) are located at similar energetic positions. While surface-bound TBA can be switched with light between its trans and cis configurations, in TBS this switching ability is lost. In TBA on Au(111), the trans f cis isomerization is driven by a substrate-mediated charge transfer process, whereby photogenerated hot holes in the Au d band lead to transient positive ion formation (transfer of the holes to the TBA HOMO level). Even though the energetic positions of the HOMOs in TBA and TBS are almost identical and thus a charge transfer should be feasible, this reaction pathway is obviously not efficient to induce the trans f cis isomerization in TBS on Au(111). Quantum chemical calculations of the potential energy surfaces for the free molecules support this conclusion. They show that cation formation facilitates the isomerization for TBA much more pronounced than for TBS due to the larger gradients at the Franck-Condon point and the much smaller barriers on the potential energy surface in the case of the TBA.

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“…Reaktionszeit: 10 Stunden 800 mg (70%) F. 6-Bis{methylthio) -4, &bis (isopentylthio) -1,3,5,7-tetrathia 6,6'-oioxo-4,4',8,8'-tetrakis(methylthio)-2,2'-bi-1,3,5,7-tetrathias-indacenyliden (13a) und 6,6'-Dioxo-4,4',8,8'-tetrakis(isopentylthio)-2,2'-bi-1,3,5,7-tetrathia-s-indacenyliden (13d) wurden nach [12] synthetisiert. 6'-Dioxo-4,4', 8,8'-tetrakis(ethylthio) -2,2'-bi-1,3,5,7- 6'-Dioxo-4,4',8,8'-tetrakis (pentylthio) -2,2'-bi-1,3,5,7-tetrathias-indacenyliden ( 1 3~) 6'-Dioxo-4,4',8,8'-tetrakis(dodecylthio)-2,2'-bi-1,3,5,7 6'-Dioxo-4,4',8,8'-tetrakis[(3',5'-di-tert-butyl) -benzylthio]-2,2'-bi-1,3,5,7-…”

Section: Bis(ethylthio)-tetrathia-s-indacen-26-dion (Lob)unclassified

“…Analog [12] werden 300 mg (0.45 mmol) 13a in einer 120°C heiBen Suspension von 400 mg NaOH in 15 ml DMSO gelost. Nach dem Abkiihlen wird das entsprechende Alkylierungsmittel im UberschuB zugesetzt und 2 Stunden nachgeriihrt.…”

Section: Allgemeine Arbeitsvorschrift Fur Die Peralkylthio-dibenzo-unclassified

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Peralkylthio-substituierte Dibenzotetrathiafulvalene (DBTTF) aus Benzolhexathiolat

et al. 1995

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Peralkylthio‐substituted Dibenzotetrathiafulvalenes (DBTTF) from Benzenehexathiolate Electrophilic and nucleophilic methylation of peralkylbenzo‐1,3‐dithiol‐2‐thiones are reported. The stable tetrakis(methylthio)‐benzo‐1,3‐dithiolium triiodide 8a is characterized by X‐ray structure analysis. The syntheses of novel 2,2′‐bi‐1,3,5,7‐tetrathia‐s‐indacenylidenes 13, 16 and mixed substituted peralkylthio‐dibenzotetrathiafulvalenes 15 are described. From selected representatives of 13, 15, 16 the ct‐complex formation, the oxidation potentials and the uv‐vis absorption range of the radical cations are reported and discussed with respect to the structures of the molecules. The electrical conductivities of the TCNQF4 complexes of 15 lie in the range of semiconductors (7·10−2–8·10−4 Scm−1).

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Photochromic Compounds with N=N and C=N Chromophores

Cited by 18 publications

References 341 publications

Quantum Chemical Investigation of Thermal Cis-to-Trans Isomerization of Azobenzene Derivatives: Substituent Effects, Solvent Effects, and Comparison to Experimental Data

Quantum Chemical Investigation of Thermal Cis-to-Trans Isomerization of Azobenzene Derivatives: Substituent Effects, Solvent Effects, and Comparison to Experimental Data

Photoisomerization Ability of Molecular Switches Adsorbed on Au(111): Comparison between Azobenzene and Stilbene Derivatives

Peralkylthio-substituierte Dibenzotetrathiafulvalene (DBTTF) aus Benzolhexathiolat

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