The targeted choice of specific photocatalysts has been shown to play a critical role for the successful realization of challenging photoredox catalytic transformations. Herein, we demonstrate the ...successful implementation of a rational design strategy for a series of deliberate structural manipulations of cyanoarene-based, purely organic donor–acceptor photocatalysts, using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a starting point. Systematic modifications of both the donor substituents as well as the acceptors’ molecular core allowed us to identify strongly oxidizing as well as strongly reducing catalysts (e.g., for an unprecedented detriflation of unactivated naphthol triflate), which additionally offer remarkably balanced redox potentials with predictable trends. Especially halogen arene core substitutions are instrumental for our targeted alterations of the catalysts’ redox properties. Based on their preeminent electrochemical and photophysical characteristics, all novel, purely organic photoredox catalysts were evaluated in three challenging, mechanistically distinct classes of benchmark reactions (either requiring balanced, highly oxidizing or strongly reducing properties) to demonstrate their enormous potential as customizable photocatalysts, that outperform and complement prevailing typical best photocatalysts.
Asymmetrically substituted tertiary phosphines and quaternary phosphonium salts are used extensively in applications throughout industry and academia. Despite their significance, classical methods to ...synthesize such compounds often demand either harsh reaction conditions, prefunctionalization of starting materials, highly sensitive organometallic reagents, or expensive transition‐metal catalysts. Mild, practical methods thus remain elusive, despite being of great current interest. Herein, we describe a visible‐light‐driven method to form these products from secondary and primary phosphines. Using an inexpensive organic photocatalyst and blue‐light irradiation, arylphosphines can be both alkylated and arylated using commercially available organohalides. In addition, the same organocatalyst can be used to transform white phosphorus (P4) directly into symmetrical aryl phosphines and phosphonium salts in a single reaction step, which has previously only been possible using precious metal catalysis.
Driven by light: A mild and facile photoredox approach towards asymmetrically substituted phosphines and phosphonium salts is reported. Blue‐light irradiation of mono‐ and diphenylphosphine with various aryl and alkyl iodides, diisopropylethylamine (DIPEA), and the organic photocatalyst 3DPAFIPN affords the desired products in good‐to‐excellent yields. In addition, the same method transforms white phosphorus (P4) directly into symmetrical aryl phosphines and phosphonium salts.
We analyze internal transition rates and the singlet–triplet energy gap of the thermally activated delayed fluorescence (TADF) molecule 3CzClIPN, which recently was introduced as an efficient ...photocatalyst. The distribution and origin of the non-monoexponential decays, which are commonly observed in TADF films, are revealed by an analysis of transient fluorescence with an inverse Laplace transform. A numerically robust global rate fit routine, which extracts all relevant TADF parameters by modeling the complete set of data, is introduced. To compare and verify the results, all methods are also applied to the well-known 4CzIPN. The influence of the molecular matrix is discussed by embedding low concentrations of TADF molecules in polystyrene films. Finally, quantum chemical calculations are compared to the experimental results to demonstrate that the chlorine atom increases the charge-transfer character of the relevant states, resulting in a reduction of the singlet–triplet energy gap.
By the on-chip integration of a droplet generator in front of an emitter tip, droplets of non-polar solvents are generated in a free jet of an aqueous matrix. When an IR laser irradiates this free ...liquid jet consisting of water as the continuous phase and the non-polar solvent as the dispersed droplet phase, the solutes in the droplets are ionized. This ionization at atmospheric pressure enables the mass spectrometric analysis of non-polar compounds with the aid of a surrounding aqueous matrix that absorbs IR light. This works both for non-polar solvents such as
n
-heptane and for water non-miscible solvents like chloroform. In a proof of concept study, this approach is applied to monitor a photooxidation of
N
-phenyl-1,2,3,4-tetrahydroisoquinoline.
Graphical abstract
By using water as an infrared absorbing matrix, analytes, dissolved in non-polar solvents from reactions carried out on a microchip, can be desorbed and ionized for investigation by mass spectrometry.
Interim Report NFDI4Chem 2023 Neumann, Steffen; Andres, Ann-Christin; Bach, Felix ...
Research Ideas and Outcomes,
07/2024, Letnik:
10
Journal Article
Recenzirano
The progress of the DFG-funded NFDI4Chem consortium (NFDI 4/1 - project number 441958208) in data management in chemistry is outlined in our latest report, highlighting the steps we have taken to ...integrate a data-centric approach within the chemistry community. This interim report offers a comprehensive overview of our data management activities, covering the reporting period from October 2020 to August 2023. The shift to digital tools in research documentation is driven by our work with Electronic Laboratory Notebooks (ELNs), such as Chemotion ELN, offering systematic data storage for easy retrieval and sharing. Additionally, we focus on developing repositories, such as Chemotion repository and RADAR4Chem , which fulfil the needs for the storage of chemical data. The NFDI4Chem Search Service ensures easy data access from our repositories. Our efforts extend to community engagement through conference visits and online presence, aimed at creating awareness for (digital) research data management and connecting to chemistry students and researchers. Our training programs have reached over 600 participants to date. Initiatives like the FAIR4Chem award and the Chemistry Data Days promote cultural change towards FAIR data. Our Editors4Chem initiative collaborates with publishers for standardised data management and the Ontologies4Chem workshops organised by our consortium promote the ontology development in the field. Apart from the consortium's engagement for chemists, NFDI4Chem members played key roles in the development of the NFDI as a whole. Being actively involved in the sections and task forces, NFDI4Chem promotes collaborative solutions across NFDI consortia.
We analyze internal transition rates and the singlet-triplet energy gap of the thermally activated delayed fluorescence (TADF) molecule 3CzClIPN, which recently was introduced as an efficient ...photocatalyst. Distribution and origin of the non-monoexponential decays, which are commonly observed in TADF films, are revealed by analysis of transient fluorescence with an inverse Laplace transform. A numerically robust global rate fit routine, which extracts all relevant TADF parameters by modeling the complete set of data, is introduced. To compare and verify the results, all methods are also applied to the well-known 4CzIPN. The influence of the molecular matrix is discussed by embedding low concentrations of TADF molecules in polystyrene films. Finally, quantum chemical calculations are compared to the experimental results to demonstrate that the chlorine atom increases the charge transfer character of the relevant states, resulting in a reduction of the singlet-triplet energy gap.
► In this we studied three different TiAlN-based multilayers deposited on differently etched steel substrates. ► Multilayer with the thickest ceramic layers has the highest hardness and lowest wear ...coefficients as well as the lowest compressive stress in the ceramic layers. ► Owing to the etching process prior coating, high adhesion of multilayers was achieved by applying a combination of MF-pulsed sputter etching followed by ion sputter etching. ► Compressive stresses were found in the coating-near substrate region, which support and fit on the subsequent deposited multilayers.
In this research work, Ti/TiAlN multilayers of various designs were deposited onto substrates pretreated by different etching procedures. The influence of multilayer design and substrate pretreatment on multilayers adhesion, hardness, wear and friction coefficients was systematically analyzed and correlated with residual stresses of these multilayers as well as with residual stresses on the coating-near substrate region, which were analyzed by synchrotron X-ray diffraction at HZB-BESSYII. These investigations show that the adhesion can be improved by a specific etching procedure, which cause increased compressive stress in the coating-near the substrate region. Additionally, it was found, that the multilayer with the thickest ceramic layers has the highest hardness and the lowest wear coefficients as well as the lowest compressive residual stress within studied multilayers.
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