Accounts of Chemical Research

Journal: Accounts of Chemical Research

Abbreviation

Acc. Chem. Res.

Publisher

American Chemical Society

ISSN

0001-4842
1520-4898

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Publications1 - 10 of 48

The Universal Role of Gallium in Promoting Methanol Formation across CO₂ Hydrogenation Catalysts
Hansen, Colin; Zhou, Wei; Copéret, Christophe (2025)
Accounts of Chemical Research
The production of value-added chemicals from CO₂ has been a thriving topic of research for the past few decades because of its contribution to a circular carbon economy. Combined with CO₂ capture and storage, thermocatalytic hydrogenation of CO₂ to CHCO₃OH with green or blue hydrogen, offers an attractive route to mitigate CO₂ emissions and to decarbonize the chemical industry. Numerous studies have been focused on catalysts based on supported metallic nanoparticles; these catalysts consist of at least one transition or coinage metal and a promoter element combined with an oxide support to disperse the active phase. Besides Zn-promoters used in Cu-based hydrogenation catalysts, numerous reports point to Ga as a promoter for methanol synthesis. In recent years, Ga has been shown to convert almost all transition metals toward selective methanol synthesis, but its specific role remains a topic of discussions. In this Account, we summarize how surface organometallic chemistry (SOMC) has enabled the discovery of novel catalysts and the development of detailed structure–activity relationships. Particularly, we show that Ga uniquely generates alloys with transition and coinage (Cu) metal elements across groups 8–11 and converts them into selective methanol synthesis catalysts. Specifically, we highlight the role of M–Ga alloy formation, alloy stability, and the formation of M(Ga)–GaOx interfaces under reaction conditions. This has been possible thanks to the combination of SOMC, which enables the formation of supported nanoparticles with tailored compositions and interfaces, and state-of-the-art characterization including operando techniques along with computational modeling, including ab initio molecular dynamic calculations. Dynamic alloying–dealloying behaviors under reaction conditions and the formation of M/MGa–GaOx interfaces are identified as key drivers for efficient methanol formation.
β-Peptidic Peptidomimetics
Seebach, Dieter; Gardiner, James (2008)
Accounts of Chemical Research
For more than a decade now, a search for answers to the following two questions has taken us on a new and exciting journey into the world of β- and γ-peptides: What happens if the oxygen atoms in a 3i-helix of a polymeric chain composed of (R)-3-hydroxybutanoic acid are replaced by NH units? What happens if one or two CH2 groups are introduced into each amino acid building block in the chain of a peptide or protein, thereby providing homologues of the proteinogenic α-amino acids? Our journey has repeatedly thrown up surprises, continually expanding the potential of these classes of compound and deepening our understanding of the structures, properties, and multifaceted functions of the natural “models” to which they are related. β-Peptides differ from their natural counterparts, the α-peptides, by having CH2 groups inserted into every amino acid residue, either between the C═O groups and the α-carbon atoms (β3) or between the α-carbon and nitrogen atoms (β2). The synthesis of these homologated proteinogenic amino acids and their assembly into β-peptides can be performed using known methods. Despite the increased number of possible conformers, the β-peptides form secondary structures (helices, turns, sheets) even when the chain lengths are as short as four residues. Furthermore, they are stable toward degrading and metabolizing enzymes in living organisms. Linear, helical, and hairpin-type structures of β-peptides can now be designed in such a way that they resemble the characteristic and activity-related structural features (“epitopes”) of corresponding natural peptides or protein sections. This Account presents examples of β-peptidic compounds binding, as agonists or antagonists (inhibitors), to (i) major histocompatibility complex (MHC) proteins (immune response), (ii) the lipid-transport protein SR-B1 (cholesterol uptake from the small intestine), (iii) the core (1−60) of interleukin-8 (inflammation), (iv) the oncoprotein RDM2, (v) the HIVgp41 fusion protein, (vi) G-protein-coupled somatostatin hsst receptors, (vii) the TNF immune response receptor CD40 (apoptosis), and (viii) DNA. Short-chain β-peptides may be orally bioavailable and excreted from the body of mammals; long-chain β-peptides may require intravenous administration but will have longer half-lives of clearance. It has been said that an interesting field of research distinguishes itself in that the results always throw up new questions; in this sense, the structural and biological investigation of β-peptides has been a gold mine. We expect that these peptidic peptidomimetics will play an increasing role in biomedical research and drug development in the near future. AB - For more than a decade now, a search for answers to the following two questions has taken us on a new and exciting journey into the world of β- and γ-peptides: What happens if the oxygen atoms in a 3i-helix of a polymeric chain composed of (R)-3-hydroxybutanoic acid are replaced by NH units? What happens if one or two CH2 groups are introduced into each amino acid building block in the chain of a peptide or protein, thereby providing homologues of the proteinogenic α-amino acids? Our journey has repeatedly thrown up surprises, continually expanding the potential of these classes of compound and deepening our understanding of the structures, properties, and multifaceted functions of the natural “models” to which they are related. β-Peptides differ from their natural counterparts, the α-peptides, by having CH2 groups inserted into every amino acid residue, either between the C═O groups and the α-carbon atoms (β3) or between the α-carbon and nitrogen atoms (β2). The synthesis of these homologated proteinogenic amino acids and their assembly into β-peptides can be performed using known methods. Despite the increased number of possible conformers, the β-peptides form secondary structures (helices, turns, sheets) even when the chain lengths are as short as four residues. Furthermore, they are stable toward degrading and metabolizing enzymes in living organisms. Linear, helical, and hairpin-type structures of β-peptides can now be designed in such a way that they resemble the characteristic and activity-related structural features (“epitopes”) of corresponding natural peptides or protein sections. This Account presents examples of β-peptidic compounds binding, as agonists or antagonists (inhibitors), to (i) major histocompatibility complex (MHC) proteins (immune response), (ii) the lipid-transport protein SR-B1 (cholesterol uptake from the small intestine), (iii) the core (1−60) of interleukin-8 (inflammation), (iv) the oncoprotein RDM2, (v) the HIVgp41 fusion protein, (vi) G-protein-coupled somatostatin hsst receptors, (vii) the TNF immune response receptor CD40 (apoptosis), and (viii) DNA. Short-chain β-peptides may be orally bioavailable and excreted from the body of mammals; long-chain β-peptides may require intravenous administration but will have longer half-lives of clearance. It has been said that an interesting field of research distinguishes itself in that the results always throw up new questions; in this sense, the structural and biological investigation of β-peptides has been a gold mine. We expect that these peptidic peptidomimetics will play an increasing role in biomedical research and drug development in the near future.
Redox Potentials and Acidity Constants from Density Functional Theory Based Molecular Dynamics
Cheng, Jun; Liu, Xiandong; VandeVondele, Joost; et al. (2014)
Accounts of Chemical Research
Expansive Quantum Mechanical Exploration of Chemical Reaction Paths
Baiardi, Alberto; Grimmel, Stephanie A.; Steiner, Miguel; et al. (2022)
Accounts of Chemical Research
Quantum mechanical methods have been well-established for the elucidation of reaction paths of chemical processes and for the explicit dynamics of molecular systems. While they are usually deployed in routine manual calculations on reactions for which some insights are already available (typically from experiment), new algorithms and continuously increasing capabilities of modern computer hardware allow for exploratory open-ended computational campaigns that are unbiased and therefore enable unexpected discoveries. Highly efficient and even automated procedures facilitate systematic approaches toward the exploration of uncharted territory in molecular transformations and dynamics. In this work, we elaborate on such explorative approaches that range from reaction network explorations with (stationary) quantum chemical methods to explorative molecular dynamics and migrant wave packet dynamics. The focus is on recent developments that cover the following strategies. (i) Pruning search options for elementary reaction steps by heuristic rules based on the first-principles of quantum mechanics: Rules are required for reducing the combinatorial explosion of potentially reactive atom pairings, and rooting them in concepts derived from the electronic wave function makes them applicable to any molecular system. (ii) Enforcing reactive events by external biases: Inducing a reaction requires constraints that steer and direct elementary-step searches, which can be formulated in terms of forces, velocities, or supplementary potentials. (iii) Manual steering facilitated by interactive quantum mechanics: As ultrafast quantum chemical methods allow for real-time manual interactions with molecular systems, human-intuition-guided paths can be easily explored with suitable human-machine interfaces. (iv) New approaches for transition-state optimization with continuous curve representations can provide stable schemes to be driven in an automated way by allowing for an efficient tuning of the curve's parameters (instead of a manipulation of a collection of structures along the path), and (v) reactive molecular dynamics and direct wave packet propagation exploit the equations of motion of an underlying mechanical theory (usually, classical Newtonian mechanics or Schrodinger quantum mechanics). Explorative approaches are likely to replace the current state of the art in computational chemistry, because they reduce the human effort to be invested in reaction path elucidations, they are less prone to errors and bias-free, and they cover more extensive regions of the relevant configuration space. As a result, computational investigations that rely on these techniques are more likely to deliver surprising discoveries.
DNA-encoded chemical libraries: Advancing beyond conventional small-molecule libraries
Franzini, Raphael M.; Neri, Dario; Scheuermann, Jörg (2014)
Accounts of Chemical Research
DNA-encoded chemical libraries (DECLs) represent a promising tool in drug discovery. DECL technology allows the synthesis and screening of chemical libraries of unprecedented size at moderate costs. In analogy to phage-display technology, where large antibody libraries are displayed on the surface of filamentous phage and are genetically encoded in the phage genome, DECLs feature the display of individual small organic chemical moieties on DNA fragments serving as amplifiable identification barcodes. The DNA-tag facilitates the synthesis and allows the simultaneous screening of very large sets of compounds (up to billions of molecules), because the hit compounds can easily be identified and quantified by PCR-amplification of the DNA-barcode followed by high-throughput DNA sequencing. Several approaches have been used to generate DECLs, differing both in the methods used for library encoding and for the combinatorial assembly of chemical moieties. For example, DECLs can be used for fragment-based drug discovery, displaying a single molecule on DNA or two chemical moieties at the extremities of complementary DNA strands. DECLs can vary substantially in the chemical structures and the library size. While ultralarge libraries containing billions of compounds have been reported containing four or more sets of building blocks, also smaller libraries have been shown to be efficient for ligand discovery. In general, it has been found that the overall library size is a poor predictor for library performance and that the number and diversity of the building blocks are rather important indicators. Smaller libraries consisting of two to three sets of building blocks better fulfill the criteria of drug-likeness and often have higher quality. In this Account, we present advances in the DECL field from proof-of-principle studies to practical applications for drug discovery, both in industry and in academia. DECL technology can yield specific binders to a variety of target proteins and is likely to become a standard tool for pharmaceutical hit discovery, lead expansion, and Chemical Biology research. The introduction of new methodologies for library encoding and for compound synthesis in the presence of DNA is an exciting research field and will crucially contribute to the performance and the propagation of the technology.
Catalytic Kinetic Resolution of Saturated N-Heterocycles by Enantioselective Amidation with Chiral Hydroxamic Acids
Kreituss, Imants; Bode, Jeffrey W. (2016)
Accounts of Chemical Research
Development of Redox-Switchable Resorcin[4]arene Cavitands
Pochorovski, Igor; Diederich, François (2014)
Accounts of Chemical Research
Olefin epoxidation with inorganic peroxides. Solutions to four long-standing controversies on the mechanism of oxygen transfer
Deubel, Dirk V.; Frenking, Gernot; Gisdakis, Philip; et al. (2004)
Accounts of Chemical Research
Iridium-Catalyzed Asymmetric Synthesis of Functionally Rich Molecules Enabled by (Phosphoramidite,Olefin) Ligandsnds
Rössler, Simon; Petrone, David A.; Carreira, Erick M. (2019)
Accounts of Chemical Research
Palladium Catalysts for Methane Oxidation: Old Materials, New Challenges
Oh, Jinwon; Boucly, Anthony; van Bokhoven, Jeroen Anton; et al. (2024)
Accounts of Chemical Research
Conspectus Methane complete oxidation is an important reaction that is part of the general scheme used for removing pollutants contained in emissions from internal combustion engines and, more generally, combustion processes. It has also recently attracted interest as an option for the removal of atmospheric methane in the context of negative emission technologies. Methane, a powerful greenhouse gas, can be converted to carbon dioxide and water via its complete oxidation. Despite burning methane being facile because the combustion sustains its complete oxidation after ignition, methane strong C-H bonds require a catalyst to perform the oxidation at low temperatures and in the absence of a flame so as to avoid the formation of nitrogen oxides, such as those produced in flares. This process allows methane removal to be obtained under conditions that usually lead to higher emissions, such as under cold start conditions in the case of internal combustion engines. Among several options that include homo- and heterogeneous catalysts, supported palladium-based catalysts are the most active heterogeneous systems for this reaction. Finely divided palladium can activate C-H bonds at temperatures as low as 150 °C, although complete conversion is usually not reached until 400-500 °C in practical applications. Major goals are to achieve catalytic methane oxidation at as low as possible temperature and to utilize this expensive metal more efficiently. Compared to any other transition metal, palladium and its oxides are orders of magnitude more reactive for methane oxidation in the absence of water. During the last few decades, much research has been devoted to unveiling the origin of the high activity of supported palladium catalysts, their active phase, the effect of support, promoters, and defects, and the effect of reaction conditions with the goal of further improving their reactivity. There is an overall agreement in trends, yet there are noticeable differences in some details of the catalytic performance of palladium, including the active phase under reaction conditions and the reasons for catalyst deactivation and poisoning. In this Account we summarize our work in this space using well-defined catalysts, especially model palladium surfaces and those prepared using colloidal nanocrystals as precursors, and spectroscopic tools to unveil important details about the chemistry of supported palladium catalysts. We describe advanced techniques aimed at elucidating the role of several parameters in the performance of palladium catalysts for methane oxidation as well as in engineering catalysts through advancing fundamental understanding and synthesis methods. We report the state of research on active phases and sites, then move to the role of supports and promoters, and finally discuss stability in catalytic performance and the role of water in the palladium active phase. Overall, we want to emphasize the importance of a fundamental understanding in designing and realizing active and stable palladium-based catalysts for methane oxidation as an example for a variety of energy and environmental applications of nanomaterials in catalysis.

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