Cyclobutane-cleavage of anti-head-to-head coumarin and quinolinone homo- and cross-dimers via single- and two-photon-absorption photochemistry

Bieniek, Nikolai; Inacker, Sebastian; Kim, Hee Cheol; Hampp, Norbert

doi:10.1016/j.jphotochem.2021.113286

Cited by 5 publications

(5 citation statements)

References 28 publications

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“…The process of dimer splitting occurs via a two-photon absorption (TPA) mechanism. The efficiency of this process depends on several factors, e.g., the molecules’ electronic structure or symmetry, the used wavelength, and the pulse duration. − Typically, short-wavelength UV light (λ < 300 nm) is used for the splitting of coumarin dimers, although this has a disadvantage: Short-wavelength UV light does not penetrate samples’ depth because of the monomeric coumarin motifs’ high absorption, as already mentioned above. Additionally, an equilibrium between cycloaddition and cycloreversion reaction is reached, leading to in complete dimer-conversion.…”

Section: Resultsmentioning

confidence: 99%

“…In detail, the sigmoidal trend can be parted into four different regimes: the first regime at low conversions is described by classical TPA-induced dimer splitting, in accordance with comparable experiments in solution. For these low conversions, a pseudo-zeroth order kinetic with linear behavior can be assumed . This process (Scheme a) is dominant for the area up to approx.…”

Section: Resultsmentioning

confidence: 99%

“…For these low conversions, a pseudo-zeroth order kinetic with linear behavior can be assumed. 47 This process (Scheme 5a) is dominant for the area up to approx. 0.2 kJ•cm −2 .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Intramolecular Coumarin-Dimer Containing Polyurethanes: Optical Tuning via Single- and Two-Photon Absorption Processes

et al. 2022

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The synthesis of an isomer-pure intramolecular coumarin dimer (ICD) in virtually unlimited amounts using a photo flow reactor is described. Based on this compound, polyurethanes with different ratios of hexamethylene diisocyanate and polytetrahydrofuran were synthesized and characterized. The reversibility of the photoinduced cycloaddition and cycloreversion reactions, one of the critical features, was compared for polymers prepared from closed ICDs and open ICDs. It was found that closed ICDs lead to a pre-orientation of the photoactive groups in the polymers, which results in a reduced loss in photoswitchable absorption. By varying the ICD content of the polymers, refractive indices ranging from 1.47 to 1.59 were achieved. With illumination, refractive index changes of Δn ≥ 0.02, as well as fluorescence changes, were achieved. Photoreactions induced by both single-photon absorption (SPA) and two-photon absorption (TPA) were studied. For the TPA-induced reaction, an autocatalytically sensitized mechanism was found. These novel polymers based on an intramolecular dimeric coumarin compound have great potential as optical materials with light-switchable properties, in particular, by TPA processes.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Intramolecular Coumarin-Dimer Containing Polyurethanes: Optical Tuning via Single- and Two-Photon Absorption Processes

et al. 2022

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“…As the process is rather inefficient, a high photon flux from intense ns-laser pulses is required to trigger the cycloreversion reaction. 15 To investigate the two-photon induced cycloreversion reaction, the same thin film of the polymer was illuminated under one photon absorption (λ = 265 nm) and two photon absorption (λ = 532 nm) characteristics. By UV-Vis measurements, the reaction was monitored in analogy to the experiments above.…”

Section: Two Photon Induced Reactionmentioning

confidence: 99%

Photo-switchable optical properties polymers with enhanced reversibility

Inacker

Hampp²

2023

Organic Photonic Materials and Devices XXV

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In the field of light-responsive polymers, coumarin is one of the most commonly used structural motifs. By applying different wavelengths, materials' properties can be changed. Hereby, limited reversibility of the reaction is reported in many cases. By introducing a novel intramolecular coumarin dimer (ICD) based polymer architecture, the reversibility of the reaction is increased significantly. The photoreaction of the reversion and addition reaction is performed over several illumination cycles with alternating UV-wavelength light (λ = 265 nm for cycloreversion, λ = 345 nm for cycloaddition). A high degree of reversibility is reached by keeping the mobility low. Performing the illumination cycles at low temperatures and using a highly crosslinked material for structural confinement, the clean photochemical reaction path is maintained. Loss of the preferred molecular orientation, e.g. by heating, resembles the coumarin moieties, which results in non-defined photoreaction and decreased reversibility. By incorporating the ICD structure in different polymers, a bunch of applications are presented. Besides light-induced refractive index modulation, also fluorescence changes in polymer thin films were achieved. In addition, the cycloreversion reaction was performed under two-photon absorption (TPA) conditions using intense visible light laser pulses. For the TPA-induced reaction, a different reaction mechanism compared to the UV-light-induced reaction was found. The TPA-induced reaction offers great potential in further applications in the field of light-responsive polymers, e.g. for optical data storage or waveguide technologies.

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“…Therefore, the value of the absorbance maximum above 300 nm can be used to follow the cycloreversion and -addition reaction. 23 In Fig. 2, two exemplary illumination series (top: cycloreversion, illumination wavelength 265 nm; bottom: cycloaddition, illumination wavelength 345 nm) and the corresponding trend in the absorbance spectra are shown.…”

Section: Monitoring Of the Intrinsic Reversible Reactionmentioning

confidence: 99%

Enhancing the photochemical reversibility of coumarin-containing polymers by molecular orientation control

2022

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Cyclobutane-cleavage of anti-head-to-head coumarin and quinolinone homo- and cross-dimers via single- and two-photon-absorption photochemistry

Cited by 5 publications

References 28 publications

Intramolecular Coumarin-Dimer Containing Polyurethanes: Optical Tuning via Single- and Two-Photon Absorption Processes

Intramolecular Coumarin-Dimer Containing Polyurethanes: Optical Tuning via Single- and Two-Photon Absorption Processes

Photo-switchable optical properties polymers with enhanced reversibility

Enhancing the photochemical reversibility of coumarin-containing polymers by molecular orientation control

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