Heterosupramolekulare Oligometallkatalysatoren: Synthese und Reaktivitätssteuerung durch Photoelektronentransfer

Eine Reihe heterodinuklearer Metallkomplexe wurde hergestellt, die aus folgenden drei Bausteinen zusammengesetzt sind: • einer photoaktiven (bpy’)2Ru(II)-Einheit mit funktionellen Gruppen (COOH, SO3H) an den 2.2’-Bipyridin-Liganden bpy’, die als Ankergruppen zur Fixierung der Komplexe auf Titandioxidschichten dienen können. • einem variablen Brückenliganden – Tetrapyridophenazin(tpphz), Bipyrimidin (bpym) oder Tripyridyltriazin (tpt) • einer katalytisch aktiven Metalleinheit (PdCl2 oder RuCl(cymol)) Die Synthesen, Strukturen, Bindungsmöglichkeiten an TiO2-Schichten und photophysikalischen Eigenschaften dieser Komplexe und von einfacher gebauten Modellverbindungen wurden ermittelt, und ihre katalytische Aktivität als Photokatalysatoren zur Reduktion von Protonen zu Wasserstoff bzw. zur Oxidation von Isopropanol zu Aceton wurde untersucht

Strategic choice of price-setting algorithms

Recent experimental simulations have shown that autonomous pricing algorithms are able to learn collusive behavior and thus charge supra-competitive prices without being explicitly programmed to do so. These simulations assume, however, that both firms employ the identical price-setting algorithm based on Q-learning. Thus, the question arises whether the underlying assumption that both firms employ a Q-learning algorithm can be supported as an equilibrium in a game where firms can chose between different pricing rules. Our simulations show that when both firms use a learning algorithm, the outcome is not an equilibrium when alternative price setting rules are available. In fact, simpler price setting rules as for example meeting competition clauses yield higher payoffs compared to Q-learning algorithms

Exploring the Full Potential of Photocatalytic Carbon Dioxide Reduction Using a Dinuclear Re2Cl2 Complex Assisted by Various Photosensitizers

Photosensitizing units have already been applied to enable light-driven catalytic reduction of CO2 with mononuclear rhenium complexes. However, dinuclear catalytic systems that are able to activate CO2 in a cooperative bimetallic fashion have only rarely been combined with photosensitizers. We here present detailed studies on the influence of additional photosensitizers on the catalytic performance of a dirhenium complex (Re2Cl2) and present correlations with spectroscopic measurements, which shed light on the reaction mechanism. The use of [Ir(dFppy)3] (Ir, dFppy=2-(4,6-difluorophenyl)pyridine)) resulted in considerably faster CO2 to CO transformation than [Cu(xant)(bcp)]PF6 (Cu, xant=xantphos, bcp=bathocuproine). Emission quenching studies, transient absorption as well as IR spectroscopy provide information about the electron transfer paths of the intermolecular systems. It turned out that formation of double reduced species [Re2Cl2]2− along with an intermediate with a Re−Re bond ([ReRe]) can be taken as an indication of multi-electron storage capacity. Furthermore, under catalytic conditions a CO2-bridged intermediate was identified.German Research FoundationDFG http://dx.doi.org/10.13039/501100001659Peer Reviewe

Eruption dynamics of Anak Krakatau volcano (Indonesia) estimated using photogrammetric methods

Open Access funding enabled and organized by Projekt DEAL.Analyzing video data from an uncrewed aerial vehicle (UAV) of two short-lived dome building events at Anak Krakatau volcano (Indonesia), we determine vertical and horizontal movements of the dome surface prior to explosions, as well as initial eruption velocities and mass eruption rates via automated feature tracking and other photogrammetric methods. Initial eruption velocities and mass eruption rates are estimated as a proxy for eruptive strength. Eruptive strength is found to correlate with deformation magnitude, i.e., larger pre-explosion surface displacements are followed by both higher initial eruption velocities and mass fluxes. In accord with other studies, our observations can be explained by an overpressure underneath the dome’s surface. We assume that the dome seals the underlying vent efficiently, meaning that pre-explosion pressure build-up controls both deformation magnitude and eruptive strength. We support this assumption by a simple numerical model indicating that pre-explosion pressure increases between 8 and 16 MPa. The model further reveals that the two events vary significantly with respect to the importance of lateral visco-elastic flow for pressurization and deformation. The video sequences also show considerable variations in the gas release and associated deformation characteristics. Both constant and accelerating deformation is observed. Our case study demonstrates that photogrammetric methods are suitable to provide quantitative constraints on both effusive and explosive activity. Future work can build on our or similar approaches to develop automated monitoring strategies that would enable the observation and analysis of volcanic activity in near real time during a volcanic crisis.We would like to thank M. Rietze, who kindly provided us with the video sequences used in this study. He also supplied all the additional information on the video acquisition without which the processing of the films would not have been possible. TD is supported by the Icelandic Research Fund grant Nr. 206527-051. Additionally, we would like to thank Michael R. James for acting as associate editor and for providing us with helpful comments on the manuscript. Likewise, we are grateful to Richard Herd and an anonymous reviewer for their constructive comments and suggestions.Pre-print (óritrýnt handrit

Correlating Heteroatoms Doping, Electronic Structures, and Photocatalytic Activities of Single‐Atom‐Doped Ag25(SR)18 Nanoclusters

Atomic‐level manipulation of catalysts is important for both fundamental studies and practical applications. Here, the central metal atom in an atomically precise Ag25 nanocluster (NC) is replaced with a single Pd, Pt, and Au atom, respectively, and employed as a model system to study the structure–property–activity relationship at the atomic level. While the geometric structures are well‐preserved after doping, the electronic structures of Ag25 NCs are significantly altered. The combination of Ag25 and TiO2 enhances the charge separation at the interface, exhibiting a 10 times higher hydrogen production rate in photocatalytic hydrogen evolution reaction compared to bare TiO2. Further results show that heteroatoms doping has a negative impact on performance, particularly in the cases of Pd and Au doping. Ultraviolet photoelectron spectroscopy measurements and density functional theory calculations suggest that the lower activities are due to an energy mismatch between the levels of doped NCs and TiO2. These findings not only reveal the impact of heteroatoms doping on the electronic properties and photocatalytic activities of NCs, but can also guide the design of heterometallic NCs for photocatalytic applications.Heteroatoms doping alters the electronic structures of Ag25 nanoclusters (NCs), while keeping the geometric structures unchanged. In this way, the geometrical effects and the electronic effects are clearly distinguished. The photocatalytic activities of as‐prepared NCs deposited onto TiO2 are investigated. The performances follow the order of Ag25 ≥ PtAg24 > PdAg24 ≥ AuAg24. image © 2023 WILEY‐VCH GmbHDFG http://dx.doi.org/10.13039/501100001659China Scholarship Council http://dx.doi.org/10.13039/501100004543Peer Reviewe

Correlating Heteroatoms Doping, Electronic Structures, and Photocatalytic Activities of Single‐Atom‐Doped Ag25(SR)18 Nanoclusters

Atomic‐level manipulation of catalysts is important for both fundamental studies and practical applications. Here, the central metal atom in an atomically precise Ag25 nanocluster (NC) is replaced with a single Pd, Pt, and Au atom, respectively, and employed as a model system to study the structure–property–activity relationship at the atomic level. While the geometric structures are well‐preserved after doping, the electronic structures of Ag25 NCs are significantly altered. The combination of Ag25 and TiO2 enhances the charge separation at the interface, exhibiting a 10 times higher hydrogen production rate in photocatalytic hydrogen evolution reaction compared to bare TiO2. Further results show that heteroatoms doping has a negative impact on performance, particularly in the cases of Pd and Au doping. Ultraviolet photoelectron spectroscopy measurements and density functional theory calculations suggest that the lower activities are due to an energy mismatch between the levels of doped NCs and TiO2. These findings not only reveal the impact of heteroatoms doping on the electronic properties and photocatalytic activities of NCs, but can also guide the design of heterometallic NCs for photocatalytic applications

Hydrogen evolution by cobalt hangman porphyrins under operating conditions studied by vibrational spectro-electrochemistry

Cobalt hangman complexes are promising catalysts for dihydrogen production, yet their electrocatalytic performance in aqueous environment is still a topic of dispute. Surface-enhanced resonance Raman (SERR) spectro-electrochemistry has a great potential to give insight into the reaction mechanism of such molecular catalysts attached to electrodes under turnover conditions. However, the intrinsic catalytic activity of plasmonic supports and photoinduced side-reactions make the in situ analysis of their structures very challenging. In this work, the structure of hangman complexes attached to electrodes via dip-coating was investigated during catalytic turnover by electrochemistry and SERR spectroscopy. In order to explore the relevance of the hanging group for proton supply, complexes bearing a carboxylic acid and an ester hanging group were compared. For the former, SERR spectra recorded under turnover conditions indicate the reductive formation of a Co^(III)–H species, followed by laser-induced translocation of a proton to the carboxylic hanging group and the associated formation of the Co^I state. Due to the lack of a proton accepting group, hangman complexes with an ester group could not be trapped in the Co^I intermediate state and as a consequence SERR spectra solely reflected the (photo-enriched) Co^(II) resting state under turnover conditions. These results represent the first Raman spectroscopic insights into intermediates of dihydrogen evolution catalysed by cobalt hangman complexes on electrodes and support the direct involvement of the hanging group as a proton shuttle

Hydrogen evolution by cobalt hangman porphyrins under operating conditions studied by vibrational spectro-electrochemistry

Cobalt hangman complexes are promising catalysts for dihydrogen production, yet their electrocatalytic performance in aqueous environment is still a topic of dispute. Surface-enhanced resonance Raman (SERR) spectro-electrochemistry has a great potential to give insight into the reaction mechanism of such molecular catalysts attached to electrodes under turnover conditions. However, the intrinsic catalytic activity of plasmonic supports and photoinduced side-reactions make the in situ analysis of their structures very challenging. In this work, the structure of hangman complexes attached to electrodes via dip-coating was investigated during catalytic turnover by electrochemistry and SERR spectroscopy. In order to explore the relevance of the hanging group for proton supply, complexes bearing a carboxylic acid and an ester hanging group were compared. For the former, SERR spectra recorded under turnover conditions indicate the reductive formation of a Co^(III)–H species, followed by laser-induced translocation of a proton to the carboxylic hanging group and the associated formation of the Co^I state. Due to the lack of a proton accepting group, hangman complexes with an ester group could not be trapped in the Co^I intermediate state and as a consequence SERR spectra solely reflected the (photo-enriched) Co^(II) resting state under turnover conditions. These results represent the first Raman spectroscopic insights into intermediates of dihydrogen evolution catalysed by cobalt hangman complexes on electrodes and support the direct involvement of the hanging group as a proton shuttle

Solution structure of stem-loop α of the hepatitis B virus post-transcriptional regulatory element

Chronic hepatitis B virus (HBV) infections may lead to severe diseases like liver cirrhosis or hepatocellular carcinoma (HCC). The HBV post-transcriptional regulatory element (HPRE) facilitates the nuclear export of unspliced viral mRNAs, contains a splicing regulatory element and resides in the 3′-region of all viral transcripts. The HPRE consists of three sub-elements α (nucleotides 1151–1346), β1 (nucleotides 1347–1457) and β2 (nucleotides 1458–1582), which confer together full export competence. Here, we present the NMR solution structure (pdb 2JYM) of the stem-loop α (SLα, nucleotides 1292–1321) located in the sub-element α. The SLα contains a CAGGC pentaloop highly conserved in hepatoviruses, which essentially adopts a CUNG-like tetraloop conformation. Furthermore, the SLα harbours a single bulged G residue flanked by A-helical regions. The structure is highly suggestive of serving two functions in the context of export of unspliced viral RNA: binding sterile alpha motif (SAM-) domain containing proteins and/or preventing the utilization of a 3′-splice site contained within SLα

Comprehensive Fragment Screening of the SARS-CoV-2 Proteome Explores Novel Chemical Space for Drug Development

12 pags., 4 figs., 3 tabs.SARS-CoV-2 (SCoV2) and its variants of concern pose serious challenges to the public health. The variants increased challenges to vaccines, thus necessitating for development of new intervention strategies including anti-virals. Within the international Covid19-NMR consortium, we have identified binders targeting the RNA genome of SCoV2. We established protocols for the production and NMR characterization of more than 80 % of all SCoV2 proteins. Here, we performed an NMR screening using a fragment library for binding to 25 SCoV2 proteins and identified hits also against previously unexplored SCoV2 proteins. Computational mapping was used to predict binding sites and identify functional moieties (chemotypes) of the ligands occupying these pockets. Striking consensus was observed between NMR-detected binding sites of the main protease and the computational procedure. Our investigation provides novel structural and chemical space for structure-based drug design against the SCoV2 proteome.Work at BMRZ is supported by the state of Hesse. Work in Covid19-NMR was supported by the Goethe Corona Funds, by the IWBEFRE-program 20007375 of state of Hesse, the DFG through CRC902: “Molecular Principles of RNA-based regulation.” and through infrastructure funds (project numbers: 277478796, 277479031, 392682309, 452632086, 70653611) and by European Union’s Horizon 2020 research and innovation program iNEXT-discovery under grant agreement No 871037. BY-COVID receives funding from the European Union’s Horizon Europe Research and Innovation Programme under grant agreement number 101046203. “INSPIRED” (MIS 5002550) project, implemented under the Action “Reinforcement of the Research and Innovation Infrastructure,” funded by the Operational Program “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014–2020) and co-financed by Greece and the EU (European Regional Development Fund) and the FP7 REGPOT CT-2011-285950—“SEE-DRUG” project (purchase of UPAT’s 700 MHz NMR equipment). The support of the CERM/CIRMMP center of Instruct-ERIC is gratefully acknowledged. This work has been funded in part by a grant of the Italian Ministry of University and Research (FISR2020IP_02112, ID-COVID) and by Fondazione CR Firenze. A.S. is supported by the Deutsche Forschungsgemeinschaft [SFB902/B16, SCHL2062/2-1] and the Johanna Quandt Young Academy at Goethe [2019/AS01]. M.H. and C.F. thank SFB902 and the Stiftung Polytechnische Gesellschaft for the Scholarship. L.L. work was supported by the French National Research Agency (ANR, NMR-SCoV2-ORF8), the Fondation de la Recherche Médicale (FRM, NMR-SCoV2-ORF8), FINOVI and the IR-RMN-THC Fr3050 CNRS. Work at UConn Health was supported by grants from the US National Institutes of Health (R01 GM135592 to B.H., P41 GM111135 and R01 GM123249 to J.C.H.) and the US National Science Foundation (DBI 2030601 to J.C.H.). Latvian Council of Science Grant No. VPP-COVID-2020/1-0014. National Science Foundation EAGER MCB-2031269. This work was supported by the grant Krebsliga KFS-4903-08-2019 and SNF-311030_192646 to J.O. P.G. (ITMP) The EOSC Future project is co-funded by the European Union Horizon Programme call INFRAEOSC-03-2020—Grant Agreement Number 101017536. Open Access funding enabled and organized by Projekt DEALPeer reviewe