Spatiotemporal dynamics of self-assembled structures in enzymatically induced agonistic and antagonistic conditions

Predicting and designing systems with dynamic self-assembly properties in a spatiotemporal fashion is an important research area across disciplines ranging from understanding the fundamental non-equilibrium features of life to the fabrication of next-generation materials with life-like properties. Herein, we demonstrate a spatiotemporal dynamics pattern in the self-assembly behavior of a surfactant from an unorganized assembly, induced by adenosine triphosphate (ATP) and enzymes responsible for the degradation or conversion of ATP. We report the different behavior of two enzymes, alkaline phosphatase (ALP) and hexokinase (HK), towards adenosine triphosphate (ATP)-driven surfactant assembly, which also results in contrasting spatiotemporal dynamic assembly behavior. Here, ALP acts antagonistically, resulting in transient self-assemblies, whereas HK shows agonistic action with the ability to sustain the assemblies. This dynamic assembly behavior was then used to program the time-dependent emergence of a self-assembled structure in a two-dimensional space by maintaining concentration gradients of the enzymes and surfactant at different locations, demonstrating a new route for obtaining 'spatial' organizational adaptability in a self-organized system of interacting components for the incorporation of programmed functionality.

Ligand-assisted Hydride Transfer: A Pivotal Step for CO2 Hydroboration Catalyzed by a Mononuclear Mn(I) PNP Complex

A mononuclear Mn(I) pincer complex [Mn(Ph₂ PCH₂ SiMe₂ )₂ NH(CO)₂ Br] was disclosed to catalyze the pinacolborane (HBpin)-based CO₂ hydroboration reaction. Density functional calculations were conducted to reveal the reaction mechanism. The calculations showed that the reaction mechanism could be divided into four stages: (1) the addition of HBpin to the unsaturated catalyst C1; (2) the reduction of CO₂ to HCOOBpin; (3) the reduction of HCOOBpin to HCHO; (4) the reduction of HCHO to CH₃ OBpin. The activation of HBpin is the ligand-assisted addition of HBpin to the unsaturated Mn(I)-N complex C1 generated by the elimination of HBr from the Mn(I) pincer catalyst. The sequential substrate reductions share a common mechanism, and every hydroboration commences with the nucleophilic attack of the Mn(I)-H to the electron-deficient carbon centers. The hydride transfer from Mn(I) to HCOOBpin was found to be the rate-limiting step for the whole catalytic reaction, with a total barrier of 27.0 kcal/mol, which fits well with the experimental observations at 90 °C. The reactivity trend of CO₂ , HCOOBpin, HCHO, and CH₃ OBpin was analyzed through both thermodynamic and kinetic analysis, in the following order, namely HCHO>CO₂ >HCOOBpin≫CH₃ OBpin. Importantly, the very high barrier for the reduction of CH₃ OBpin to form CH₄ reconciles with the fact that methane was not observed in this catalytic reaction.

Computational mechanistic insights into non-noble-metal-catalysed CO2 conversion

The conversion of CO2 into liquid fuels and value-added fine chemicals is of significant interest for both the environment and the global energy demand. In this frontier article, we highlight viable methods for transforming CO2 into valuable C1 feedstocks and summarize the key mechanistic aspects obtained by in-depth computational investigations of three important pathways of two-electron CO2 reduction: (i) CO2 dissociation to CO (ii) CO2 dimerization to CO32- and CO, and (iii) CO2 hydrogenation to formate. Lastly, we present our outlook on how theoretically obtained mechanistic insights could be translated into strategies for designing efficient non-noble-metal catalysts for CO2 reduction.

The potential of d6 non-noble metal NHC catalysts for carbon dioxide hydrogenation: group and row effects

Group VIB NHC-complexes as promising non-noble catalysts for CO₂ hydrogenation benefiting by the weak electronegativity and low oxidation state.

Homogeneously catalyzed hydrogenation and dehydrogenation reactions – From a mechanistic point of view

Homogeneously catalyzed hydrogenation/dehydrogenation reactions represent not only one of the most synthetically important chemical transformations, but also a promising way to renewably utilize the hydrogen energy. In order to rationally design efficient homogeneous catalysts for hydrogenations/dehydrogenations, it is of fundamental importance to understand their reaction mechanisms in detail. With this aim in mind, we herein provide a brief overview of the mechanistic understanding and related catalyst design strategies. Hydrogenations and dehydrogenations represent the reverse process of each other, and involve the activation/release of H2 and the insertion/elimination of hydride as major steps. The mechanisms discussed in this chapter include the cooperation (bifunctional) mechanism and the non-cooperation mechanisms. Non-cooperation mechanisms usually involve single-site transition metal (TM) catalysts or transition metal hydride (TM-H) catalysts. Cooperation mechanisms usually operate in the state-of-the-art bifunctional catalysts, including Lewis-base/transition-metal (LB-TM) catalysts, Lewis-acid/transition-metal (LA-TM) catalysts, Lewis-acid/Lewis-base (LA-LB; the so-called frustrated Lewis pairs - FLPs) catalysts, newly developed ambiphilic catalysts, and bimetallic transition-metal/transition-metal (TM-TM) catalysts. The influence of the ligands, the electronic structure of the metal, and proton shuttle on the reaction mechanism are also discussed to improve the understanding of the factors that can govern mechanistic preferences. The content presented in this chapter should both inspire experimental and theoretical chemists concerned with homogeneously catalyzed hydrogenation and dehydrogenation reactions, and provide valuable information for future catalyst design.

Flexible proton-responsive ligand-based Mn(i) complexes for CO2 hydrogenation: a DFT study

Significance of a flexible proton responsive ligand to the dihydrogen (H⋯H) bond for CO₂ hydrogenation.

DFT study of CO2 hydrogenation catalyzed by a cobalt-based system: an unexpected formate anion-assisted deprotonation mechanism

An unexpected formate anion-assisted deprotonation mechanism is unfolded by a DFT study of CO₂ hydrogenation catalyzed by a cobalt-based system.

Aliphatic Mn–PNP complexes for the CO2 hydrogenation reaction: a base free mechanism

Aliphatic amido Mn–PNP-based complexes were found to be promising for CO₂ hydrogenation reaction.

Experimental and Quantum Mechanical Study of Nucleophilic Substitution Reactions of meta- and para-Substituted Benzyl Bromides with Benzylamine in Methanol: Synergy Between Experiment and Theory

This work involves the experimental and theoretical study of the nucleophilic substitution of meta- and para-substituted benzyl bromides with benzylamine. Conductometric rate experiments confirm the applicability of the Hammett linear free-energy relationship to this system. To gain a deep understanding of the physical chemistry at play, a quantum mechanical study of the reaction is also conducted. The quantum mechanical calculations not only reproduce the experimental free energy of activation, but also provide greater insights at the molecular and atomic level. Isolation of the calculated transition state structure and application of the Hammett equation to its electronic, structural, and energetic properties are studied.

Insight into the stereoelectronic parameters of N-triphos ligands via coordination to tungsten(0)

A series of new N-triphos tungsten complexes have been synthesised and structurally characterised.

Aqueous biphasic iron-catalyzed asymmetric transfer hydrogenation of aromatic ketones

For the first time, an iron(ii) catalyst is used in the biphasic asymmetric transfer hydrogenation (ATH) of ketones to enantioenriched alcohols employing water and potassium formate as the proton and hydride source, respectively.