Abstract Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum catalysts for the oxygen reduction reaction (ORR) in fuel cells; however, their active site structures remain poorly understood. A postulate is that iron-containing sites exist primarily a pyridinic Fe-N 4 ligation environment, yet, molecular model generally feature pyrrolic coordination. Herein, we report hexaazacyclophane macrocycle, (phen 2 N )Fe, compare its spectroscopic,...

Establishing catalytic structure–function relationships introduces the ability to optimize catalyst structure for enhanced activity, selectivity, and durability against reaction conditions prolonged catalysis. Here we present experimental computational data elucidating mechanism O2 reduction with a conductive nickel-based metal–organic framework (MOF). Elucidation of electrokinetics, understanding role extended MOF in providing observation how redox activity pKa organic ligand influences...

The mean-field solutions of electronic excited states are much less accessible than ground state (e.g., Hartree-Fock) solutions. Energy-based optimization methods for states, like Δ-SCF (self-consistent field), tend to fall into the lowest solution consistent with a given symmetry—a problem known as “variational collapse.” In this work, we combine ideas direct energy-targeting and variance-based in order describe at level. resulting method, σ-SCF, has several advantages. First, it allows one...

Fragment embedding is one way to circumvent the high computational scaling of accurate electron correlation methods. The challenge applying fragment molecular systems primarily lies in strong entanglement and that prevent fragmentation across chemical bonds. Recently, Schmidt decomposition has been shown effective for fragments are strongly coupled a bath several model systems. In this work, we extend recently developed quantum scheme, bootstrap (BE), resulting method utilizes matching...

Using a combination of experimental and computational investigations, we assemble consistent mechanistic model for the oxygen reduction reaction (ORR) at molecularly well-defined graphite-conjugated catalyst (GCC) active sites featuring aryl-pyridinium moieties (N+-GCC). ORR catalysis glassy carbon surfaces modified with N+-GCC fragments displays near-first-order dependence in O2 partial pressure near-zero-order on electrolyte pH. Tafel analysis suggests an equilibrium one-electron transfer...

When developing machine learning models for yield prediction, the two main challenges are effectively exploring condition space and substrate space. In this article, we disclose an approach mapping Ni/photoredox-catalyzed cross-electrophile coupling of alkyl bromides aryl in a high-throughput experimentation (HTE) context. This model employs active (in particular, uncertainty querying) as strategy to rapidly construct model. Given vastness space, focused on that builds initial then uses...

Fragment embedding approaches offer the possibility of accurate description strongly correlated systems with low-scaling computational expense. In particular, wave function have demonstrated ability to subdivide across highly entangled regions, promising wide applicability for a number challenging systems. this paper, we focus on method Bootstrap Embedding, extending it Pariser–Parr–Pople and 2D Hubbard models in order evaluate behaviour that are less amenable local fragment embedding. We...

We report a systematic study on the gas-phase polymerization of ethylene by metal–organic framework (MOF) catalyst. Cr3+-exchanged MFU-4l (Cr(III)-MFU-4l, = Zn5Cl4(BTDD)3, H2BTDD bis(1H-1,2,3,-triazolo[4,5-b],[4′,5′-i])dibenzo[1,4]dioxin)) serves as an exemplary system to demonstrate prereaction treatment with alkylaluminum species simple method isolate active MOF catalyst for liquid-free ethylene. AlMe3-treated Cr(III)-MFU-4l subjected 40 bar exhibits activity 52 000...

Graphite-conjugated catalysts (GCCs) are a promising class of materials that combine many the advantages heterogeneous and homogeneous catalysts. In particular, GCCs containing an aryl-pyridinium active site appear to be effective nonmetal for oxygen reduction reaction (ORR). this study, we analyzed both structural electronic properties dataset molecules nitrogen atoms embedded in aromatic order understand which enable particular bind O2, is necessary step initiation ORR. We found carbon...

The idea of using fragment embedding to circumvent the high computational scaling accurate electronic structure methods while retaining accuracy has been a long-standing goal for quantum chemists. Traditional mainly focus on systems composed weakly correlated parts and are insufficient when division across chemical bonds is unavoidable. Recently, density matrix theory (DMET) other based Schmidt decomposition have emerged as fresh approach this problem. Despite their success model systems,...

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures poorly understood. A postulate is that iron sites this class of exist an Fe-N 4 pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination are, best our knowledge, non-existent. We report synthesis characterization a hexaazacyclophane macrocycle, (phen 2 N )Fe,...

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures poorly understood. A postulate is that iron sites this class of exist an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination are, best our knowledge, non-existent. We report synthesis characterization a hexaazacyclophane...

This work explores the relationship between theoretically predicted excitation energies and experimental molar absorption spectra as they pertain to environmental aquatic photochemistry. An overview of pertinent Quantum Chemical descriptions sunlight-driven electronic transitions in organic pollutants is presented. Second, a combined molecular dynamics (MD), time-dependent density functional theory (TD-DFT) analysis ultraviolet visible (UV-Vis) six model compounds presented alongside...

Lattice models are a useful tool to simulate the kinetics of surface reactions. Since it is expensive propagate probabilities entire lattice configurations, practical consider occupation typical site or cluster sites instead. This amounts moment closure approximation chemical master equation. Unfortunately, simple closures, such as mean-field and pair (PA), exhibit weaknesses in systems with significant long-range correlation. In this paper, we show that machine learning (ML) can be used...

Graphite-conjugated catalysts (GCC) are a class of highly synthetically tunable materials with properties both homogeneous and heterogeneous catalysts. GCCs have proven especially promising for catalyzing the oxygen reduction reaction (ORR). In this study, we applied density functional theory (DFT) to explore how group aromatic scaffold modifications affect catalytic activity ORR. We found that kinds can significant enough effect on tune ORR rate determining step between strong weak binding...

Graphite-conjugated catalysts (GCCs) are a class of highly synthetically tunable materials with properties both homogeneous and heterogeneous catalysts. GCCs have proven especially promising for catalyzing the oxygen reduction reaction (ORR). In this study, we applied density functional theory (DFT) to explore how group aromatic scaffold modifications affect catalytic activity ORR. We found that kinds can significant enough effect on tune ORR rate-determining step between strong weak binding...

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures poorly understood. A postulate is that iron sites this class of exist an Fe-N 4 pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination are, best our knowledge, non-existent. We report synthesis characterization a hexaazacyclophane macrocycle, (phen 2 N )Fe,...

Graphite-conjugated catalysts (GCCs) are a promising class of materials that combine many the advantages heterogenous and homogeneous catalysts. In particular, GCCs containing an aryl-pyridinium active site appear to be effective nonmetal for oxygen reduction reaction (ORR). this study, we analyzed both structural electronic properties dataset molecules nitrogen atoms embedded in aromatic order understand which enable particular bind O2, is necessary step initiation ORR. We found carbon...