A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• setup for isomerization quantum yield determination is reported. The setup combines fiber-coupled LEDs, a commercially calibrated thermopile detector for measurement of the photon flux, and a fiber-coupled UV–vis spectrometer. By solving the rate equations numerically, isomerization quantum yields can

• actinometry, thus demonstrating the reliability of our setup. Keywords: isomerization; molecular photoswitches; photochemistry; photon flux; UV–vis spectroscopy; Introduction Photoswitches are molecules that can undergo a light-driven structural rearrangement to populate a metastable state of the initial

• photon flux, i.e., the number of photons impinging a unit area of the sample in a unit of time [10]. Potassium ferrioxalate [39][40] is one of the most used actinometers while also some azobenzene derivatives have been reported as reaction quantum yield standards [11][22]. Although new chemical

Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• evolution using a Pt-loaded polymeric carbon nitride photocatalyst under 365 nm irradiation in the presence of sacrificial reducing agents. The fluid flow pattern of the developed photoreactor was characterized experimentally and the photon flux incident to the loop photoreactor was measured by chemical

• actinometry. The system displayed exceptional stability, with operation sustained over 70 hours. A design of experiment (DOE) analysis was used to systematically investigate the influence of key parameters – photon flux, photocatalyst loading, stirring speed, and inert gas flow rate – on the hydrogen

• generation rate. Linear relationships were found between hydrogen evolution rate and photon flux as well as inert gas flow rate. Photocatalyst loading and stirring speed also showed linear correlations, but could not be correctly described by DOE analysis. Instead, linear single parameter correlations could

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• from Shimadzu (GC-2030) equipped with two barrier discharge ionization detectors (BID). Every test was repeated at least twice. The photon flux was evaluated with actinometry, according to a previously published procedure [42], and it was 0.025 µE s−1. Therefore, an apparent photoluminescent quantum

Heterogeneous metallaphotoredox catalysis in a continuous-flow packed-bed reactor

• Wei-Hsin Hsu,
• Susanne Reischauer,
• Peter H. Seeberger,
• Bartholomäus Pieber and
• Dario Cambié

Beilstein J. Org. Chem. 2022, 18, 1123–1130, doi:10.3762/bjoc.18.115

• uniformity and activity, while partially homogeneous systems would need downstream separations. We used in-line reaction monitoring to study several process parameters, such as time, temperature and the photon flux, to maximize the throughput and evaluate the long-term stability of this catalytic approach

• the free induction decay (FID) files, respectively. The reaction was run until stable conditions were obtained, defined as seven consecutive spectra in which the coefficient of variation (CV) of the auto-integrated product yield was below 3%. Residence time, photon flux and temperature studies Having

• distribution significantly improves the transformation compared with the batch reaction. Next, we investigated if the reaction rate significantly depends on the received photon flux (Table 1). For these studies, we chose a residence time of 3 hours (i.e., 10 µL/min flow rate) as a compromise between conversion

Control over size, shape, and photonics of self-assembled organic nanocrystals

• Chen Shahar,
• Yaron Tidhar,
• Yunmin Jung,
• Haim Weissman,
• Sidney R. Cohen,
• Ronit Bitton,
• Iddo Pinkas,
• Gilad Haran and
• Boris Rybtchinski

Beilstein J. Org. Chem. 2021, 17, 42–51, doi:10.3762/bjoc.17.5

• of the exciton–exciton annihilation process, occurring when a high photon flux results in multiple excitons, which can efficiently diffuse through the aggregated material, resulting in exciton annihilation [51]. In order to validate the observed behavior and prove that the measured differences

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

• , energy efficiency is not a concern. Optimal photon flux should be provided to make sure that the reactor is operated without light transfer limitations. In addition, the utilization of one microchannel or a capillary tube would be enough as long as there is adequate mixing to overcome mass transfer

• increased the apparent reaction rate by a 4-fold compared to an iron packing material [68]. Therefore, a translucent material should be preferred in photoreactors. The photon flux received by the absorbing species needs to be determined accurately in order to characterize photochemical reactors. The

• serpentine-shaped photomicroreactor. The photon flux per liquid volume was shown to increase exponentially with the amount of gas inside the channels. The conversion was significantly affected by the liquid distribution inside the channels rather than the light scattering or the liquid mixing. In that work

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• in mol L−1 s−1, Φco is the ring opening quantum yield, i.e., the number of events divided by the number of photons absorbed and Ia is the rate of photon absorption, in mol L−1 s−1, i.e., the photon flux per volume of solution to be measured. Note that for a given reactor of volume V, the photon flux

• per volume of solution is related to the photon flux J by a simple multiplication J = I × V. The difficulty is then to relate the rate of absorbed photons Ia to the incident photon flux J0 emitted by the UCNPs. A way to circumvent this issue is to adapt actinometer solution absorbance to the reactor

• the ratio where J0 is the above measured photon flux and JaNIR is 976 nm laser photon flux absorbed by the nanoparticles: where P is the laser power in Watts and J0NIR the NIR photon flux. Additionally, one can access the number of emitted photons per particles J0/nNP (in photon s−1), or, using the

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• chain mechanism was further confirmed by calculating the quantum yield (Φ) because a chain process provides multiple equivalents of product per photon absorbed by the photocatalyst (Φ > 1). The photon flux of blue LED (λmax = 469 nm) was determined using the potassium ferrioxalate actinometer [57][58

Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

• Serge Pérez and
• Daniele de Sanctis

Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

• concept of photons and the ability to overcome the inherent dilution problems encountered in batch. The ability to control residence times and hence decrease secondary transformations whilst using the small dimensions of the microreactor flow streams to enhance the photon flux has been claimed to increase

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• photochemical reaction in the studied system: Φ = (rate of substrate conversion)/(absorbed photon flux) Theoretically, if a simple photocatalytic process is considered, the quantum yield would be in the range 0 < Φ ≤ 1. It approaches unity as the efficiency of the photocatalytic step increases. In reality

• answers to the distinction between photocatalytic and radical chain mechanisms can be derived directly from Φ. A quantification of the photon flux is rather problematic. Recently, devices became available which use solar cells for the direct measurement of photon fluxes [33]. However, chemical actinometry

• constitutes a prevalent indirect method of photon flux measurement [34]. Several effective chemical actinometers are known for UV spectral studies whereas similar experiments in the visible range are much more limited by the availability of chemical actinometers. Even more challenging are photon flux

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• -pressure lamp, if operating at 30% efficiency will have a total UV power of 4.5 W at 254 nm. According to Equation 3 this corresponds to a photon flux of 34 mmol photons per hour. When multiplied by the quantum yield of a reaction driven by 254 nm UV, a figure is obtained that represents the maximum

• as a stream (flux). As the reactant solution is also introduced as a stream, the flow rate can be precisely tailored to match the photon flux of the lamp and the quantum yield of the substrate. The main aim of this review is to illustrate the advances made in flow photochemistry over the last 10