1, 8a‐Dihydroindolizine als Komponenten neuer photochromer Systeme

Hauck, Gerd; Dürr, Heinz

doi:10.1002/ange.19790911218

Cited by 45 publications

(12 citation statements)

References 7 publications

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“…It is evident from Table that rate constant of 4.40 × 10 −3 < k < 5.42 × 10 −3 s −1 at 293 K corresponds to k 2 in Scheme unimolecular thermal back reaction. Note that these values are in excellent agreement with the literature 4.90 × 10 −3 s −1 21d, 27 . According to our results, the kinetics of the electrocyclic back reaction of the betaines to the DHI are dictated by the ring closure of the betaine.…”

Section: Resultsmentioning

confidence: 99%

“…[4][5][6][7][8][9][10] So far, a variety of photochromic materials, such as spirobenzopyrans, [11] chromenes, [12] diarylethenes, [13] and dihydroindolizine and tetrahydroindolizine, [14][15][16][17][18][19][20][21][22] have been developed to meet the requirements of optoelectronic devices. Among the well-known photochromic families, dihydroindolizines (DHIs), which discovered and developed by Dürr in 1979, are promising candidates for optoelectronic devices, data storage, dental filling materials, and DNA markers. [17] They are exhibiting excellent fatigue resistance, good thermal stability, high sensitivity, and rapid response in solution, polymeric thin films, and in solid media.…”

Section: Introductionmentioning

confidence: 99%

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Photochromism of dihydroindolizines Part XIX. Efficient one-pot solid-state synthesis, kinetic, and computational studies based on dihydroindolizine photochromes

Ahmed

Guesmi

Asghar

et al. 2016

J. Phys. Org. Chem.

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For the first time, one‐pot solid‐state synthesis of 12 photochromic materials based on photochromic dihydroindolizine system substituted in both fluorene part (region A) and the heterocyclic part (region C) has been established. This method has immense advantages, which are short‐time reaction, high‐yield and low‐yield by‐products, and easily purification and separation processes. In addition, this method will help in getting over the tremendously purification and low‐yield problems faced since the worth‐finding of this family of photochromic materials. The absorption maxima (λmax) and the half‐lives (t1/2) of the colored betaines were detected in all cases using multichannel UV/Vis spectrophotometric measurements. The rate constants of the thermal back reaction of the betaines were determined at constant temperature by measuring the decrease in the maximum absorption intensity (λmax) with time. The half‐lives (t1/2) and rate constants (k) of betaines under examination were calculated by plotting lnA against time (t). The kinetic measurements could be detected by both spectra scan and time‐dependent decay measurements. Examination of the Arrhenius parameters reveals an underlying compensation between Ea and log A, whereby an increase in Ea is opposed by an increase in log A. The compensation appears in the corresponding Eyring parameters, ΔH≠ and ΔS≠; betaine structural changes that lead to lower, more favorable enthalpies of activation engender opposing entropic changes. At the isokinetic temperature Tiso = β, structural changes do not affect the rate constant of a reaction series because the changes of ΔH≠ are counterbalanced by changes of ΔS≠. The existence of an isokinetic relationship indicates a common structure of the transition state of all thermal back reaction of betaine under investigation. The computational results suggest that the decoloration reaction is a two‐step mechanism. The first step corresponds to the transoid–cisoid isomerization with an activation barrier of 10.3 kJ mol−1, and the second step is the ring closure from the cisoid intermediate with a barrier 71.3 kJ mol−1, which represent the rate determining step for thermal decoloration. The photochemical ring opening of DHIs to betaines is a disrotatory 1,5‐electrocyclic reaction, whereas the thermal ring‐closing occurs in the conrotatory mode. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photochromism of dihydroindolizines Part XIX. Efficient one-pot solid-state synthesis, kinetic, and computational studies based on dihydroindolizine photochromes

Ahmed

Guesmi

Asghar

et al. 2016

J. Phys. Org. Chem.

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“…It is possible to analyze the thermal relaxation of the photochromism in a polymer matrix above its glass transition temperature on the basis of the WLF eq~ati0n.l~ Indeed, this equation correlates the viscosity-temperature coefficient of a polymer to its T ' , and was already applied previously to the photochromism of azobenzenes and spirobenzopyrans linked to amorphous bulk polymers.". 1 On the basis of the expression" plots of the left-hand term against (2' -Tg)-' are linear with the intercept at the ordinates and slope permitting the evaluation of the constants C, and C,.…”

Section: Resultsmentioning

confidence: 99%

Photochromism of spirofluorenylindolizines

Deblauwe

Smets

1989

J. Polym. Sci. A Polym. Chem.

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The decoloration kinetics of three spirofluorenylindolizines have been followed in solution and in polymer matrix. They are the 5′‐methyl‐spiro[9H‐fluorene‐9.1′(1′H)‐indolizine]‐2′‐3′‐bis‐methoxycarbonyl (I), its methacryloyl oxymethyl (II) derivative, and the copolymers of (II) with ethyl acrylate. In solution the reactions follow first‐order kinetics and show pronounced negative solvatochromism. In solid polymer film, the incorporation of the photochrome as side group of polyethylacrylate affects strongly the decoloration below Tg of the film. Above Tg the decoloration was interpreted on the basis of the WLF equation.

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“…Molecular switches can be built using supramolecular or LC photochromic materials. 1 Photochromic polymers can be used in phototropic glasses or as a basis for information recording. IR-sensitive materials have been made using biphotochromic molecules.…”

Section: Discussionmentioning

confidence: 99%