Photochemistry of di-tert-butyl ketone and structural effects on the rate and efficiency of intersystem crossing of aliphatic ketones

Yang, N. C.; Feit, E. D.; Hui, Man Him; Turro, Nicholas J.; Dalton, J. Christopher

doi:10.1021/ja00726a046

Cited by 96 publications

(23 citation statements)

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“…Given the lack of an obvious IR absorbance component due to R6G -with its contributions overwhelmed by the polymer -it is difficult to say definitively that observed changes are due to the dye and/or host. However, we find that the observed changes are consistent with previous studies of photodegradation in neat PU [56][57][58][59][60][61][62] and therefore we proceed with the assumption that the changes in the IR absorbance spectrum are due to the polymer and not the dye. Figure 16 shows the change in IR absorbance of the sample due to conditioning and degradation.…”

Section: Ftir Measurementssupporting

confidence: 84%

Photodegradation and self-healing in a Rhodamine 6G dye and $$\hbox {Y}_{2}\hbox {O}_{3}$$ nanoparticle-doped polyurethane random laser

2015

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One of the fundamental difficulties in implementing organic dyes in random lasers is irreversible photodegradation of the dye molecules, leading to loss of performance and the need to replace the dye. We report the observation of self-healing after photodegradation in a Rhodamine 6G dye and nanoparticle doped polyurethane random laser. During irradiation we observe two distinct temporal regions in which the random lasing (RL) emission first increases in intensity and redshifts, followed by further redshifting, spectral broadening, and decay in the emission intensity. After irradiation the emission intensity is found to recover back to its peak value, while still being broadened and redshifted, which leads to the result of an enhancement of the spectrally integrated intensity. We also perform IR-VIS absorbance measurements and find that the results suggest that during irradiation some of the dye molecules form dimers and trimers and that the polymer host is irreversibly damaged by photooxidation and Norrish type I photocleavage.

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Section: Ftir Measurementssupporting

confidence: 84%

Photodegradation and self-healing in a Rhodamine 6G dye and $$\hbox {Y}_{2}\hbox {O}_{3}$$ nanoparticle-doped polyurethane random laser

2015

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“…The actual error is likely to be larger as a result of errors in the fixed parameters; most notably, in the rate constant of intersystem crossing for adamantanone and the rate constant for the nonradiative decay of triplet adamantanone (see the Supporting Information). Modeling also revealed that the contribution to the sensitized chemiluminescence from triplets formed by intersystem crossing from the singlets is negligible, thanks in part to a relatively slow intersystem crossing rate compared with other alkyl ketones 34…”

Section: Resultsmentioning

confidence: 99%

Dioxetane Scission Products Unchanged by Mechanical Force

Clough

Sijbesma

2014

ChemPhysChem

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Dioxetane-based force-induced light emission from polymers, or mechanoluminescence, is a powerful new way of characterizing the behavior of polymeric materials under stress. Here, we reveal that breaking the dioxetane mechanically gives strikingly similar products to those formed on thermal activation, with a singlet/triplet ratio of 1:9.9 and a total quantum yield of 9.8%. A sensitized relay scheme ensured high reproducibility in the detection of the short-lived triplet products. In addition to guiding the design of more sensitive mechanoluminescent probes, the similarity in the scission products indicates that once mechanical force releases the steric lock between the adamantyl groups, the dioxetane undergoes scission in a pathway that resembles the thermal process. Excited states are formed only after the main transition state in a region in which the excited- and ground-state surfaces are nearly degenerate, which, thus, accounts for the remarkable similarity in the scission products.

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“…On the other hand, the rate of bond breaking in the parent triplet of the related molecule CH3COCH(CH3) 2 is known to be sufficiently fast to compete with spin-lattice relaxation in the triplet, so as to make this a potential source of TM spin polarization [24]. Unequivocal experimental evidence for a TM contribution is given in radicals created from chlorine-substituted propanone molecules, below.…”

Section: Dialkyl Ketonesmentioning

confidence: 99%

The photochemistry of propanone and its derivatives as studied using flash-photolysis ESR; electron spin polarization (CIDEP) in radical products

Batchelor¹,

Kay²,

McLauchlan³

et al. 1994

Molecular Physics

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By direct observation of the transient radical products of the flash photolysis of ketones related to propanone, three different primary reactions have been demonstrated. Propanone and butanone exhibit both Norrish type 1 and hydrogen-abstraction reactions whose relative contributions depend upon the solvent used, but 3,3-dimethyl-2-butanone exhibits a dominant bond scission (Norrish type 1) reaction. Ketones with hydroxyl substituents exhibit only the latter reaction, as it appears do those with chlorine substituents, but in these, in contrast to the others, it is the 13 bond which breaks. This might suggest a change in the character of the triplet state from which the radicals are produced from n~* to ~rt*. The CIDEP observed is consistent with this interpretation. Most spectra exhibit net polarization whose phase varies with the nature of the substituent, and which originates in the triplet mechanism. The significance of the observations to the controversial polarization observed in the propanone ketyl radical produced in the reactions of propanone with a suitable hydrogen source is discussed. Unusual observations of acyl radicals are reported, with some resolved hyperfine structure,

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Photochemistry of di-tert-butyl ketone and structural effects on the rate and efficiency of intersystem crossing of aliphatic ketones

Cited by 96 publications

References 0 publications

Photodegradation and self-healing in a Rhodamine 6G dye and $$\hbox {Y}_{2}\hbox {O}_{3}$$ nanoparticle-doped polyurethane random laser

Photodegradation and self-healing in a Rhodamine 6G dye and $$\hbox {Y}_{2}\hbox {O}_{3}$$ nanoparticle-doped polyurethane random laser

Dioxetane Scission Products Unchanged by Mechanical Force

The photochemistry of propanone and its derivatives as studied using flash-photolysis ESR; electron spin polarization (CIDEP) in radical products

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