Photochemische Umlagerungen in der Triphenyl‐methan‐Reihe

Lifschitz, J.

doi:10.1002/cber.19190520916

Cited by 31 publications

(12 citation statements)

References 5 publications

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“…leuconitriles where the CN group is bound to the spiro-carbon atom only. The photophysics and photochemistry of triarylmethane leuconitriles (TAMCN) have been a topic of extensive interest and dispute, 25 and it has been known for a long time that these compounds undergo photoinduced dissociation of the C-CN bond to yield dye cations, 26 being the sources of instantaneous colour. The photodissociation reaction in TAMCNs is critically dependent on solvent polarity (no dye formation in solvents with e below 4.5) 27 and proceeds from thermally equilibrated S 1 excited state 28 in competition with fluorescence and intersystem crossing.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced electron transfer in malachite green lactoneDedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays.

Karpiuk

2003

Phys. Chem. Chem. Phys.

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The spectroscopy and photophysics of malachite green lactone (MGL), a lactonic form of the well-know malachite green dye, have been studied as functions of solvent polarity in aprotic and protic solvents at different temperatures in solution and in glass. It has been found that MGL photophysics substantially differs from that of other malachite green leucoderivatives (e.g. leuconitrile, leucohydroxide or halides). In aprotic solvents ultrafast intramolecular electron transfer (estimated t ET 130 fs) between MGL structural components (from initially excited insulated dimethylaniline, DMA, to phthalide, Pd) results in formation of a highly polar (25.0 D) intramolecular CT state which then emits fluorescence. The dynamics of the primary ET are determined mainly by intramolecular vibrational motions and not by the solvation process. The polar nature of the emitting state was verified with the solvatochromic method, and S n S 1 transient absorption spectra prove that charge separation results in formation of DMA radical cation in MGL. The separation of charges is maintained in the charge transfer triplet state, which lies below the local triplet levels of MGL structural components, making MGL a unique candidate for studying both CT triplet state and CT-singlet-triplet dynamics. The electronic structure of the 1 CT state stabilizes charge separation in moderately polar solvents (e.g. F fl and t fl in butyl acetate (BA) are 0.12 and 23.8 ns, respectively) and no evidence has been found for photodissociation of C-O bond in lactone ring in aprotic solvents, which is the dominant photoprocess in malachite green leuconitrile or halides. Further increase of solvent polarity results in dramatic enhancement of MGL nonradiative deactivation from the 1 CT state (increase in k nr by two orders of magnitude on going from BA to ACN) pointing to a solvent polarity-driven deactivation channel. The strong dependence of CT fluorescence quantum yield on CT transition energy found in supercooled and in glassy butyronitrile (BTN), where conformational motions are restricted, suggests that the nonradiative decay is (i) not related to conformational changes and (ii) consists in enhancement of nonradiative return electron transfer (direct radiationless charge recombination), which is proven by the good linear correlation between ln k nr and ñ n fl in more polar solvents (energy gap law). The large temperature-dependent blue shift of the fluorescence maximum in BTN below the melting point (rigidochromism) makes MGL a very sensitive probe for studying reorientation polarization in rigid and semi-rigid supercooled media.y Dedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays.

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Section: Introductionmentioning

confidence: 99%

Photoinduced electron transfer in malachite green lactoneDedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays.

Karpiuk

2003

Phys. Chem. Chem. Phys.

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“…Photochemical reactions involving the intermediary formation of carbocations have long been known . Almost a century ago, Lifschitz and Joffé reported the heterolytic photocleavage of amino‐substituted 2,2,2‐triarylacetonitriles in alcoholic solution to the corresponding tritylium ions and cyanide, and observed the subsequent slow disappearance of the carbocations (Scheme (a)) . However, the rate constants for the reactions of these tritylium ions with cyanide could be measured more conveniently by simply mixing solutions of the tritylium ions with a solution of CN − …”

Section: Historic Perspectivementioning

confidence: 99%

Photogeneration of carbocations: applications in physical organic chemistry and the design of suitable precursors

Ammer

Mayr

2013

J of Physical Organic Chem

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The generation of carbocations by laser flash photolysis of suitable precursors provides information about their reactivities toward nucleophiles on the nanosecond and microsecond time scale that cannot be obtained by conventional methods. We discuss the requirements that must be met by the precursors to achieve sufficient yields of the carbocations under the conditions of kinetic experiments. These include (i) efficient photogeneration of the carbocations; (ii) the stability of the precursor in the sample solution; (iii) the absorption of the precursor at the excitation wavelength; and (iv) sufficient lifetimes of the photogenerated carbocations for the observation of their reactivities toward the nucleophiles of interest. We provide an overview of the advantages and disadvantages of some precursors that are commonly employed for the generation of carbocations R + . This includes alkyl halides R-Cl, acetates R-OAc, aryl ethers R-OAr, ammonium salts R-NR 0 3 + , and phosphonium salts R-PR 0 3 + .

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“…The color produced by the action of light on alcoholic solutions of pararosaniline cyanide was spectroscopically examined and compared with the color of pararosaniline chloride. The conclusion was reached that the two colors were identical (36,42,44). In the same way the colors of a light stimulated solution of rosaniline sulfite and rosaniline chloride were compared, and the conclusion was also the two colors were identical (34).…”

Section: The Color Changementioning

confidence: 96%

“…These ideas have been extended by others, especially as regards the relation of ionization to color (50). Following this idea of dual forms of the dye derivatives, Lifschitz believes that the colorless form is stable in the dark in solution but that the action of light converts it into the colored form (42). He has followed through, as already described, the relation between the development of color in the light and the development of electrical conductivity in the solutions of these dyestuff derivatives.…”

Section: The Color Changementioning

confidence: 99%

Phototropy.

Chalkley¹

1929

Chem. Rev.

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Photochemische Umlagerungen in der Triphenyl‐methan‐Reihe

Cited by 31 publications

References 5 publications

Photoinduced electron transfer in malachite green lactoneDedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays.

Photoinduced electron transfer in malachite green lactoneDedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays.

Photogeneration of carbocations: applications in physical organic chemistry and the design of suitable precursors

Phototropy.

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