Photochemical Data Research Articles

Mechanistic Interrogation of Photochemical Nickel-Catalyzed Tetrahydrofuran Arylation Leveraging Enantioinduction Data

Mechanistic Interrogation of Photochemical Nickel-Catalyzed Tetrahydrofuran Arylation Leveraging Enantioinduction Data

Perspective on Theoretical and Experimental Advances in Atmospheric Photochemistry.

Research that explores the chemistry of Earth's atmosphere is central to the current understanding of global challenges such as climate change, stratospheric ozone depletion, and poor air quality in urban areas. This research is a synergistic combination of three established domains: earth observation, for example, using satellites, and in situ field measurements; computer modeling of the atmosphere and its chemistry; and laboratory measurements of the properties and reactivity of gas-phase molecules and aerosol particles. The complexity of the interconnected chemical and photochemical reactions which determine the composition of the atmosphere challenges the capacity of laboratory studies to provide the spectroscopic, photochemical, and kinetic data required for computer models. Here, we consider whether predictions from computational chemistry using modern electronic structure theory and nonadiabatic dynamics simulations are becoming sufficiently accurate to supplement quantitative laboratory data for wavelength-dependent absorption cross-sections, photochemical quantum yields, and reaction rate coefficients. Drawing on presentations and discussions from the CECAM workshop on Theoretical and Experimental Advances in Atmospheric Photochemistry held in March 2024, we describe key concepts in the theory of photochemistry, survey the state-of-the-art in computational photochemistry methods, and compare their capabilities with modern experimental laboratory techniques. From such considerations, we offer a perspective on the scope of computational (photo)chemistry methods based on rigorous electronic structure theory to become a fourth core domain of research in atmospheric chemistry.

Dual role of dissolved black carbon in sensitized ofloxacin photooxidation: Mechanism and influential factors

Dissolved black carbon (DBC) is the more photoactive component of dissolved organic matter (DOM) pool, which plays a dual role in the photoconversion of aquatic contaminants, acting as both a photosensitizer and an inhibitor. However, little is known about the more systematic mechanism by which DBC exhibits a dual effect, which is closely related to the structure composition of DBC. In this study, the differences in characteristics of DBC obtained from 300 °C and 500 °C were compared via UV–vis absorption spectrum, Fluorescence excitation emission matrix spectra (3D-EEM), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS), and evaluated the promoting and inhibiting effects of DBC on ofloxacin (OFL) photodegradation. It was found that higher pyrolysis temperature reduced the UV absorbance, molecular weight, aromaticity, and phenolics of DBC while increasing the content of quinone/aromatic ketone and humic substances. Photochemical data showed that 3DBC*, 1O2 and ·OH were all participated in the DBC-mediated OFL photodegradation. Wherein, DBC300 (DBCT, where T = pyrolysis temperature) had strong light screening and dynamic quenching effect, but the formation ability of 3DBC*, 1O2 and ·OH was poor, which significantly retarded the photodegradation of OFL. While DBC500 exhibited a slight promotion effect due to its higher formation ability of reactive species and weak light screening effect. Moreover, DBC500 had higher steady-state concentration and (kOFL,3DBC⁎) than DBC300, which might be due to the higher contents of quinone/aromatic ketone and the lower contents of phenol in DBC500, thus enhancing the reactivity of 3DBC* and OFL. Our research systematically revealed the trade-off mechanism of DBC on the photodegradation of fluoroquinolones, and provided an important theoretical guidance for the photodegradation of fluoroquinolones under the evolution of DBC composition.

Inferring the Molecular Basis for Dissolved Organic Matter Photochemical and Optical Properties.

Despite the widespread use of photochemical and optical properties to characterize dissolved organic matter (DOM), a significant gap persists in our understanding of the relationship among these properties. This study infers the molecular basis for the optical and photochemical properties of DOM using a comprehensive framework and known structural moieties within DOM. Utilizing Suwannee River Fulvic Acid (SRFA) as a model DOM, carboxylated aromatics, phenols, and quinones were identified as dominant contributors to the absorbance spectra, and phenols, quinones, aldehydes, and ketones were identified as major contributors to radiative energy pathways. It was estimated that chromophores constitute ∼63% w/w of dissolved organic carbon in SRFA and ∼47% w/w of overall SRFA. Notably, estimations indicate the pool of fluorescent compounds and photosensitizing compounds in SRFA are likely distinct from each other at wavelengths below 400 nm. This perspective offers a practical tool to aid in the identification of probable chemical groups when interpreting optical and photochemical data and challenges the current "black box" thinking. Instead, DOM photochemical and optical properties can be closely estimated by assuming the DOM is composed of a mixture of individual compounds.

Marine Plant Growth Promoting Bacteria (PGPB) inoculation technology: Testing the effectiveness of different application methods to improve tomato plants tolerance against acute heat wave stress

Regenerative agriculture aims to boost native biodiversity and ensure sustainable production. Plant Growth Promoting Bacteria (PGPB) enhance crop yield through improved nutrient use efficiency or stress tolerance. Utilizing synthetic bacterial communities (SynCom) tailored to specific challenges holds promise for enhancing plant resilience. However, challenges include designing microbial consortia and selecting SynCom application techniques. This study tested four PGPB SynCom application methods on tomato plants to evaluate their effectiveness in promoting plant resistance and recovery from short extreme heat waves. Non-invasive phenotyping techniques were used to assess plant responses to three delivery methods (watering, foliar spray, and alginate spheres immobilization) under heat stress. Plants treated with the marine PGPB SynCom through methods like leaf spraying or encapsulation in alginate spheres exhibited improved resilience in terms of Kautsky curve intensity and shape, indicating better photochemical apparatus function. These techniques also facilitated post-stress recovery. Deep photochemical analysis revealed SynCom-induced improvements in the plant's photochemical apparatus, particularly the PS II donor side. Moreover, it was also possible to observe that upon stress relief these two techniques, alongside the plants inoculated throughout watering were able to recover their photochemical profiles. Analysing the Fv/Fm values, plants inoculated through watering, alginate beads and leaf spray can be considered heat-tolerant, a characteristic conserved throughout the three sampling moments. Heat-wave exposure led to an increase in the energy absorbed by the non-inoculated plants as a counteractive measure to overcome the low energy use efficiency observed (low trapping and transported energy fluxes). The reduction in stress impact was attributed to SynCom's ACC-deaminase production, which lowered ethylene accumulation, promoting growth and photosynthetic efficiency. The study also noted reduced energy dissipation under stress relief, indicating efficient heat dissipation mechanisms due to SynCom application. Statistical models generated with the attained photochemical data allowed depicting specific fluorescence signatures of each thermal and inoculation treatment with a very high degree of accuracy, reinforcing that these different inoculation treatments have in fact different impacts on plant photochemistry but also provide a tool for future phenotyping assessments using the proposed inoculation techniques. Alginate bead based PGPB release emerged as an efficient, scalable technique with continuous benefits for plant growth and stress response.

Dose-Response Activity-Based DNA-Encoded Library Screening.

Dose-response, or "conforming" behavior, increases confidence in a screening hit's authenticity. Here, we demonstrate dose-response solid-phase DNA-encoded library (DEL) screening. Compound dose in microfluidic droplets is modulated via the UV intensity of photocleavage from DEL beads. A 55,296-member DEL was screened at different UV intensities against model enzyme drug targets factor Xa (FXa) and autotaxin (ATX). Both screens yielded photochemical dose-dependent hit rates (FXa hit rates of 0.08/0.05% at 100/30% UV exposure; ATX hit rates of 0.24/0.08% at 100/20% UV exposure). FXa hits contained structures reflective of FXa inhibitors and four hits inhibited FXa (IC50 = 4.2 ± 0.1, 7.4 ± 0.3, 9.0 ± 0.3, and 19 ± 2 μM.) The top ATX hits (two dihydrobenzamidazolones and a tetrahydroisoquinoline) were validated as inhibitors (IC50 = 7 ± 2, 13 ± 2, and 1 ± 0.3 μM). Photochemical dose-response DEL screening data prioritized hits for synthesis, the rate-limiting step in DEL lead identification.

Molecular and Crystal Structure, Spectroscopy, and Photochemistry of a Dispiro Compound Bearing the Tetraoxane Pharmacophore.

The molecular structure and photochemistry of dispiro[cyclohexane-1,3'-[1,2,4,5]tetraoxane-6',2''-tricyclo[3.3.1.13,7 ]decan]-4-one (TX), an antiparasitic 1,2,4,5-tetraoxane was investigated using matrix isolation IR and EPR spectroscopies, together with quantum chemical calculations undertaken at the DFT(B3LYP)/6-311++G(3df,3pd) level of theory, with and without Grimme's dispersion correction. Photolysis of the matrix-isolated TX, induced by in situ broadband (λ>235 nm) or narrowband (λ in the range 220-263 nm) irradiation, led to new bands in the infrared spectrum that could be ascribed to two distinct photoproducts, oxepane-2,5-dione, and 4-oxohomoadamantan-5-one. Our studies show that these photoproducts result from initial photoinduced cleavage of an O-O bond, with the formation of an oxygen-centered diradical that regioselectivity rearranges to a more stable (secondary carbon-centered)/(oxygen-centered) diradical, yielding the final products. Formation of the diradical species was confirmed by EPR measurements, upon photolysis of the compound at λ=266 nm, in acetonitrile ice (T=10-80 K). Single-crystal X-ray diffraction (XRD) studies demonstrated that the TX molecule adopts nearly the same conformation in the crystal and matrix-isolation conditions, revealing that the intermolecular interactions in the TX crystal are weak. This result is in keeping with observed similarities between the infrared spectrum of the crystalline material and that of matrix-isolated TX. The detailed structural, vibrational, and photochemical data reported here appear relevant to the practical uses of TX in medicinal chemistry, considering its efficient and broad parasiticidal properties.

Photochemical study and vibrational spectra of propiolamide isolated in low-temperature Ar, Xe, and N2 matrices

Propiolamide (HCCCONH2, PA) has been isolated in low-temperature matrices (Ar, Xe, and N2) and studied by matrix isolation infrared (IR) spectroscopy and quantum chemical calculations undertaken at the DFT(B3LYP)/6-311++G(d,p) level of theory. In situ broadband UV light (λ > 235 nm) irradiation of matrix-isolated PA led to the observation of new bands ascribed to different photoproducts resulting from three distinct photoreaction pathways: (i) tautomerization to propiolimidic acid (HCCC(OH)NH), (ii) CC bond cleavage, with formation of acetylene (HCCH) and isocyanic acid (HNCO), and (iii) decarbonylation, leading to generation of ethynamine (HCCNH2). Pathways (i) and (ii) were observed in all matrices, while (iii) was only observed in the matrices of the rare gases. Observation of characteristic bands due to the different photoproducts has been established, and the assignment of the IR spectra for all the species was carried out. As a whole, the detailed structural, vibrational, and photochemical data reported in this article appear relevant to the rational practical use of PA in its multiple application areas (in particular in the pharmaceutical and materials sciences domains) as well as for its analytical determination, including its search in the interstellar space.

A comparison of investigations into the photovoltaic and electronic properties of the zinc-containing photoanodes for DSC applications

The study aimed to explore the possibility of using zinc oxide (ZO), zinc titanate (ZT), and zinc stannate (ZS) as alternative photoanode materials for DSC. The sol-gel process was used to synthesize the three materials. The prepared materials were characterized structurally by PXRD. UV-Visible spectroscopy was used to evaluate the absorption properties, dye loading, and aggregation behaviour of bare dye and dye-adsorbed photoanodes. As a result, ZS-based photoanodes have a high adsorption capacity (44 nmol/mg) and are less prone to aggregation. The photoelectric conversion behaviour of the materials was explored under one sunlight condition. It shows that ZS-based photoanodes have a higher photocurrent of 4.21 mA/cm 2 , a photovoltage of 0.613 V, and a better PCE of 1.66%, which can be attributed to the strong dye adsorption capacity of ZS. Similarly, photochemical data show a low R ct resistance and a high chemical capacitance for ZS. Zinc orientated with tin is viewed as a future DSC material that is less aggregative, low-cost, and high-performance than other derivatives. The details are presented herein. • An efficient comparison in PCE was conducted between several zinc-incorporated photoanodes (ZnO, ZnTiO 3 and ZnSnO 3 ). • The various photoanodes with zinc insertion were thoroughly examined regarding their electrochemistry and optical characteristics. • Zinc stannate (ZS) based photoanode exhibits higher device performance and is noted as a prospective candidate for DSC's future.

Fabrication of Bi4Ti3O12/ZnIn2S4 S-scheme heterojunction for achieving efficient photocatalytic hydrogen production

Photocatalytic hydrogen production from water splitting is a technology that takes advantage of solar energy to produce clean and green hydrogen energy with wide application prospects. Herein, an S-scheme heterojunction photocatalyst with a nanosheets-on-nanosheets structure was successfully prepared by using a simple low-temperature water bath method and ZnIn2S4 nanosheets are generated in situ on Bi4Ti3O12 nanosheets, realizing efficient photocatalytic produce hydrogen under visible light irradiation. The optimal proportion of Bi4Ti3O12/ZnIn2S4 (BTO/ZIS) has extraordinary hydrogen production efficiency of 19.8 mmol h−1 g−1, 2.1 times that of pristine ZIS (9.2 mmol h−1 g−1). The main reasons for the improved activity of BTO/ZIS heterojunction photocatalysts are investigated by a series of photochemical characterization data analyses. Finally, its high photocatalytic performance can be attributed to more reactive active sites provided by the sheet-sheet heterostructure and the formation of S-scheme heterojunction between BTO and ZIS, which promotes the transfer of photogenerated electron-hole pairs.

Electronic Absorption Spectroscopy and Photochemistry of Criegee Intermediates.

Interest in Criegee intermediates (CIs), often termed carbonyl oxides, and their role in tropospheric chemistry has grown massively since the demonstration of laboratory-based routes to their formation and characterization in the gas phase. This article reviews current knowledge regarding the electronic spectroscopy of atmospherically relevant CIs like CH2 OO, CH3 CHOO, (CH3 )2 COO and larger CIs like methyl vinyl ketone oxide and methacrolein oxide that are formed in the ozonolysis of isoprene, and of selected conjugated carbene-derived CIs of interest in the synthetic chemistry community. Of the aforementioned atmospherically relevant CIs, all except CH2 OO and (CH3 )2 COO exist in different conformers which, under tropospheric conditions, can display strikingly different thermal loss rates via unimolecular and bimolecular processes. Calculated photolysis rates based on their absorption properties suggest that solar photolysis will rarely be a significant contributor to the total loss rate for any CI under tropospheric conditions. Nonetheless, there is ever-growing interest in the absorption cross sections and primary photochemistry of CIs following excitation to the strongly absorbing 1 ππ* state, and how this varies with CI, with conformer and with excitation wavelength. The later part of this review surveys the photochemical data reported to date, including a range of studies that demonstrate prompt photo-induced fission of the terminal O-O bond, and speculates about possible alternate decay processes that could occur following non-adiabatic coupling to, and dissociation from, highly internally excited levels of the electronic ground state of a CI.

Unlocking Kautsky’s dark box: Development of an optical toxicity classification tool (OPTOX index) with marine diatoms exposed to emerging contaminants

Chlorophyll a induction curves, or Kautsky curves, have been extensively used to study physiological stress conditions in phototrophic organisms, with the analysis of several derived parameters. Nevertheless, these variables use only about 10 % of the information comprised in the complete Kautsky curve dataset, leaving 90 % of the photochemical data within an underutilized dark box, that is not translated into photochemically relevant variables. By observing the variable fluorescence profiles from marine diatoms exposed to a myriad of emerging and classical contaminants, several fluorescence profile alterations were detected, with significant deviations from the control conditions concomitant with the degree of growth inhibition imposed by the chemical stressor. The Linear Discriminant Analysis (LDA) analysis based on the normalized variable chlorophyll a fluorescence profiles revealed a high discriminatory efficiency of the type of contaminant to which the cultures were exposed, indicating that the exposure to different chemical stressors (contaminants) results in specific fluorescence profiles that can be used as descriptors of these exposure conditions. Analysing the individual contaminant LDA analysis, a very low overlap between samples exposed to different concentrations was observed, indicating a high discriminatory power of the variable fluorescence profiles. When evaluating the blind-test classification efficiencies, provided by this contaminant-specific LDA approach, it was possible to observe a high degree of efficiency in almost all contaminants tested, and for most of the concentrations applied. With this in mind, the produced linear discriminants and proportion of traces was used to compute an optical toxicity classification tool - the OPTOX index. The index revealed a high degree of correlation with the growth inhibition observed and/or with the exogenous dose of contaminant applied. The developed OPTOX index, a unifying tool enclosing all the fluorescence data provided by the chlorophyll a induction curve, proved to be an efficient tool to apply in ecotoxicological assays using marine model diatoms with a high degree of reliability for classifying the exposure of the cells to emerging contaminants. Additionally, the data analysis pipeline, as well as the index development methodology here proposed, can be easily transposed to other autotrophic organisms subjected to different ecotoxicological test conditions calibrated and validated against known biochemical or morphological descriptors of stress, integrating this way a large amount of data that was until know completely overlooked and left within an underutilized and undervalued dark box.

Lipid Data Acquisition for devices Treatment of Coronary Diseases Health stuff on the Internet of Medical Things

Recently, the widespread deployment of smart phones globally, biomedical diagnostics. Smartphone-based devices are expected to be commonly used Intelligent Health Tracking Point-of-Care (PoC) Internet of Medical Things (IoMT) applications. As a result, this paper presents a smartphone-based blood lipid data acquisition dongle for measuring blood lipid levels such as TC, HDL-C, and triglycerides (TG). Blood loss in the fingertip to manage coronary artery disease. A thin photochemical during detection. The test strip, composed of LEDs and detectors, is plugged into a small dongle where the colour switches. The intensities of the calculated reflective coefficient of the lipide determinant are indicated. The product of chromogenics. Such photochemical data acquisition data dongle was focused on smart phones. Validated and achieved a correlation coefficient above 0.843 by reference to a clinical analyzer and summed. 5.017 per unit variance coefficient (CV) for 93 blood lipid patients assessment. The photochemistry Therefore, dongle is promising for the potential treatment of IoMT chronic diseases.

Evaluated kinetic and photochemical data for atmospheric chemistry: volume VIII – gas-phase reactions of organic species with four, or more, carbon atoms ( ≥ C4)

Abstract. This article, the eighth in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers the gas-phase thermal and photochemical reactions of organic species with four, or more, carbon atoms (≥ C4) available on the IUPAC website in 2021, including thermal reactions of closed-shell organic species with HO and NO3 radicals and their photolysis. The present work is a continuation of volume II (Atkinson et al., 2006), with new reactions and updated data sheets for reactions of HO (77 reactions) and NO3 (36 reactions) with ≥ C4 organics, including alkanes, alkenes, dienes, aromatics, oxygenated, organic nitrates and nitro compounds in addition to photochemical processes for nine species. The article consists of a summary table (Table 1), containing the recommended kinetic parameters for the evaluated reactions, and a supplement containing the data sheets, which provide information upon which recommendations are made.

A kinetic study of the photooxidation of water by aqueous cerium(IV) in sulfuric acid using a diode array spectrophotometer

The photooxidation of water by aqueous cerium(IV) has been investigated in dilute sulfuric acid quantitatively using a diode array spectrophotometer. An overview of experimental data on the speciation of cerium(IV) showed that several different absorbing species are present under almost all conditions, which makes straightforward interpretation of photochemical data very difficult. At submillimolar levels of cerium(IV) in 0.10 mol dm–3 sulfuric acid, a consistent quantum yield of 0.12 for the loss of cerium(IV) could be determined, but even under these conditions, clear evidence of a parallel non-photochemical pathway was obtained. At higher concentrations of the metal ion, significant deviations from the expected direct proportionality between the illumination ratio and the initial rate were confirmed, which can only be interpreted by a complicated system of parallel, coupled photochemical and non-photochemical pathways. The inhibitory effect of aqueous cerium(III) in the process was also demonstrated. Based on indirect evidence, it seems likely that sulfate ion radicals play a significant role in the mechanism.

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume VII – Criegee intermediates

Abstract. This article, the seventh in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers an extension of the gas-phase and photochemical reactions related to Criegee intermediates previously published in Atmospheric Chemistry and Physics (ACP) in 2006 and implemented on the IUPAC website up to 2020. The article consists of an introduction, description of laboratory measurements, a discussion of rate coefficients for reactions of O3 with alkenes producing Criegee intermediates, rate coefficients of unimolecular and bimolecular reactions and photochemical data for reactions of Criegee intermediates, and an overview of the atmospheric chemistry of Criegee intermediates. Summary tables of the recommended kinetic and mechanistic parameters for the evaluated reactions are provided. Data sheets summarizing information upon which the recommendations are based are given in two files, provided as a Supplement to this article.

UV/Vis+ photochemistry database: Structure, content and applications

The “science-softCon UV/Vis+ Photochemistry Database” (www.photochemistry.org) is a large and comprehensive collection of EUV-VUV-UV–Vis-NIR spectral data and other photochemical information assembled from published peer-reviewed papers. The database contains photochemical data including absorption, fluorescence, photoelectron, and circular and linear dichroism spectra, as well as quantum yields and photolysis related data that are critically needed in many scientific disciplines.This manuscript gives an outline regarding the structure and content of the “science-softCon UV/Vis+ Photochemistry Database”. The accurate and reliable molecular level information provided in this database is fundamental in nature and helps in proceeding further to understand photon, electron and ion induced chemistry of molecules of interest not only in spectroscopy, astrochemistry, astrophysics, Earth and planetary sciences, environmental chemistry, plasma physics, combustion chemistry but also in applied fields such as medical diagnostics, pharmaceutical sciences, biochemistry, agriculture, and catalysis. In order to illustrate this, we illustrate the use of the UV/Vis+ Photochemistry Database in four different fields of scientific endeavor.

Spectroscopic, photophysical and photochemical properties of newly metallo-phthalocyanines containing coumarin derivative

The new, well-soluble and non-aggregated peripheral or non-peripheral tetra-ethyl 7-oxy-4,8-dimethylcoumarin-3-propanoate substituted magnesium (II), zinc (II) and indium (III) acetate phthalocyanines were synthesized. They were characterized by widely known spectroscopic methods such as UV–vis, IR, MALDI-TOF Mass, 1H NMR spectroscopies and elemental analysis. Photophysical and photochemical properties were studied in N, N-dimethylformamide to determine the usability of each of these phthalocyanines as photosensitizers. The influences of the position and presence of the coumarin derivative at the phthalocyanine skeleton and metal’ nature in the phthalocyanine cavity on photophysical and photochemical properties were investigated by comparing with previous analogues (magnesium, zinc, and indium phthalocyanines containing coumarin derivative with different functional groups). The spectroscopic, photophysical, photochemical data and results obtained for each of these phthalocyanines show that they may have the potential to be used as photosensitizers in photodynamic therapy.

Phototoxic risk assessment of dermally-applied chemicals with structural variety based on photoreactivity and skin deposition

Combined use of photochemical and pharmacokinetic (PK) data for phototoxic risk assessment was previously proposed, and the system provided reliable phototoxic risk predictions of chemicals in same chemical series. This study aimed to verify the feasibility of the screening system for phototoxic risk assessment on dermally-applied chemicals with wide structural diversity, as a first attempt. Photochemical properties of test chemicals, 2-acetonaphthalene, 4′-methylbenzylidene camphor, 6-methylcoumarin, methyl N-methylanthranilate, and sulisobenzone, were evaluated in terms of UV absorption and reactive oxygen species (ROS) generation, and PK profiles of the test chemicals in rat skin were characterized after dermal co-application. All test chemicals showed strong UVA/B absorption with molar extinction coefficients of over 3000 M−1⋅cm−1, and irradiated 2-acetonaphthalene, 6-methylcoumarin, and methyl N-methylanthranilate exhibited significant ROS generation. Dermally-applied 2-acetonaphthalene and 4′-methylbenzylidene camphor indicated high and long-lasting skin deposition compared with the other test chemicals. Based on the photochemical and PK data, 2-acetonaphthalene was predicted to have potent phototoxic risk. The predicted phototoxic risk of the test chemicals by integration of obtained data was mostly consistent with their in vivo phototoxicity observed in rat skin. The screening strategy employing photochemical and PK data would have high prediction capacity and wide applicability for photosafety evaluation of chemicals.

Automated generation of photochemical reaction data by transient flow experiments coupled with online HPLC analysis

Competing homo- and crossdimerization reactions between coumarin and 1-methyl-2-quinolinone are investigated by transient continuous-flow experiments combined with online HPLC, enabling the generation and acquisition of large reaction data sets.