Facile Quantum Yield Determination via NMR Actinometry

Ji, Yining; DiRocco, Daniel A.; Hong, Cynthia; Wismer, Michael K.; Reibarkh, Mikhail

doi:10.1021/acs.orglett.8b00391

Cited by 60 publications

(62 citation statements)

References 20 publications

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“…Lastly, the NMR actinometry methodology has been successfully applied to a ferrioxalate actinometer (Scheme ) despite its paramagnetic nature through direct CO 2 detection . The avoidance of a step involving derivatization of weakly absorbing photolysis products to strongly absorbing compounds significantly simplifies experimental procedures compared to the classical ferrioxalate actinometry protocol.…”

Section: Applicationsmentioning

confidence: 99%

“…It is worth to note that the concentration dependence curve also allows for the extraction of the operating linear absorption regime for the study of intrinsic reaction kinetics (Figure ) . In order to avoid the photon‐limited regime, the concentration of the light‐absorbing molecules should be low enough relative to the photon flux to ensure the reaction rate was not limited by a lack of photons.…”

Section: Applicationsmentioning

confidence: 99%

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LED‐Illuminated NMR Spectroscopy: A Practical Tool for Mechanistic Studies of Photochemical Reactions

DiRocco

Kind

et al. 2019

ChemPhotoChem

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This Concept article highlights the development of a novel analytical tool, LED-NMR (a combination of in situ light illumination using a light-emitting diode and NMR spectroscopy) and its variant UVNMR (LED-NMR coupled with UV/Vis absorption spectroscopy), as well as their applications in the mechanistic investigation of light-induced transformations. The utility of these new tools has been demonstrated by providing rich kinetic and structural data of reaction species offering mechanistic insights into photochemical and photocatalytic reactions. Furthermore, NMR actinometry has been recently developed as a practical and simple method for quantum yield measurements. Quantum yield is an important parameter in photoinduced processes, but is rarely measured in practice because of the barriers associated with traditional actinometry. These new tools and techniques streamline measurements of the quantum efficiency while affording informative mechanistic insights into photochemical reactions. We anticipate these techniques will enable chemists to further advance the rapidly emerging photochemistry field. adoption of LED-NMR will make this powerful technique a standard method in the field of photochemistry.

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Section: Applicationsmentioning

confidence: 99%

Section: Applicationsmentioning

confidence: 99%

LED‐Illuminated NMR Spectroscopy: A Practical Tool for Mechanistic Studies of Photochemical Reactions

DiRocco

Kind

et al. 2019

ChemPhotoChem

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“…Actinometers can be used to characterize a light source by using a reaction with a known quantum yield to calculate the number of photons absorbed. A number of actinometry reactions have been reported, but we have failed to identify a simple way to operate the system that covers a wide range of wavelengths 9,10 . With this in mind, we are calling for a procedurally simple homogeneous actinometry reaction that is applicable to both batch and flow photoreactors.…”

Section: Stark-einstein Law or Photoequivalence Lawmentioning

confidence: 98%

Photons as a 21st century reagent

et al. 2020

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A pharmaceutical industry viewpoint on how the fundamental laws of photochemistry are used to identify the parameters required to implement photochemistry from lab to scale. Parameters such as photon stoichiometry and light intensity are highlighted within to inform future publications. Photochemistry employs photons to drive chemical transformations. Traditional approaches rely on the direct excitation of bonds with light 1,2. In contrast, photoredox catalysis uses a photosensitizer to facilitate electron transfer, generating reactive intermediates under mild conditions 3. From a pharmaceutical industry point-of-view, photochemistry is a powerful tool to access highenergy intermediates that can provide novel reactivity and enables new disconnections, allowing target-and diversity-oriented synthesis to be explored 4. Photochemistry is extensively used within medicinal chemistry projects, but has not yet been extensively employed for the commercial manufacture of pharmaceutical agents 5. The scientific community has published new and exciting photochemical methods, but in our experience these transformations can be challenging to reproduce 3,6. We believe that this difficulty results from an under-emphasized importance of fundamental photochemical concepts, which renders translation of methods between setups challenging. Most authors try to describe the key features of the photochemical system used in their experiments; however, the description may not be completely sufficient to ensure reproducibility in a different lab or comparable reactor system. It can be quite common to find little technical detail about the equipment setup in the Supplementary Information and many summaries fall short of fully characterizing the photo-physical properties of their setup. We believe that careful characterization and description of the photochemistry equipment is essential; more systematic and better documented experimentation will enable greater mechanistic understanding, leading to facile identification of the key scale-up factors. From a review of the fundamentals of photochemistry, we will detail the minimum information to include in any photochemistry-related publication. This will enable the chemistry community to more readily assess and adopt photochemical transformations. We will then look toward the future of photochemistry for a manufacturing system that applies this technology. Grotthuss-Draper law Light must be absorbed by a chemical substance for a photochemical reaction to occur. Photon absorption excites a molecule from its ground state to an excited state. Chemical substances only absorb at specific wavelengths, so it is critical that the right wavelength is selected for the desired transformation.

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“…This method of calibration is not only easier, but also more accurate than the regular method, which only employs the use of an actinometer and has typical error margins of around 10%. [7,24,25] In this case, by using spectrometric methods to determine the received photon flux, the margin of error is reduced significantly.…”

Section: Cross-currentmentioning

confidence: 99%

Principles of coaxial illumination for photochemical reactions: Part 2. Model validation

Meir

Leblebici

Kuhn

et al. 2020

J Adv Manuf & Process

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This study reports the principles and model equations for co-and counter-current illumination, validated by experimental data. Current photochemical reactors which are homogeneously illuminated suffer from a light efficiency problem resulting in low light absorption and subsequent low productivity. Hence, the use of co-and counter-current illuminated reactors, implementing larger path lengths, without altering the reactor's geometry, is of interest. In this article, we report a simple model to determine the conversion obtained by co-and counter-current illumination techniques and compare against the current state-of-the-art. Via experimental validation, we report the use of co-and counter-current illumination to significantly boost the PSTY, a measure for photochemical reactor productivity, by a factor of 5 to 6 for same input concentration of reagent, solemnly by illuminating the reactor via co-and countercurrent (axially) instead of cross-current (radially). Furthermore, we report that simply increasing the reagent concentration, thus absorbance, has a large influence on productivity, thus PSTY, of the reactor. By assessing the reactor's performance parameters, derived by modeling, which are the initial absorbance value (A) and the quantum photon balance (ρϕ), the reactor's operating point can be determined and adapted to operate in a more productive and efficient regime.

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Facile Quantum Yield Determination via NMR Actinometry

Cited by 60 publications

References 20 publications

LED‐Illuminated NMR Spectroscopy: A Practical Tool for Mechanistic Studies of Photochemical Reactions

LED‐Illuminated NMR Spectroscopy: A Practical Tool for Mechanistic Studies of Photochemical Reactions

Photons as a 21st century reagent

Principles of coaxial illumination for photochemical reactions: Part 2. Model validation

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