Robert Pollice#RobSelects paper of the week #ScienceMagazine: Single-molecule vibrational spectroscopy via tunable femtosecond infrared excitation and cryogenic ultra-high vacuum scanning tunneling microscopy. #physchem https://doi.org/10.1126/science.adz6643
#RobSelects paper of the week #J_A_C_S: X-ray induced Coulomb explosion imaging of the hydrogen atom positions in individual thiophenone molecules. #physchem https://doi.org/10.1021/jacs.5c08730
Visualizing the Three-Dimensional Arrangement of Hydrogen Atoms in Organic Molecules by Coulomb Explosion Imaging
Structure-sensitive methods based on femtosecond light or electron pulses are now making it possible to measure how molecular structures change during light-induced processes. Despite significant progress, high-fidelity imaging of nuclear positions remains a challenge even for relatively small molecular systems and, notably, regarding the positions of hydrogen atoms. As demonstrated in recent work, X-ray-induced Coulomb explosion imaging (CEI) may overcome this obstacle, as its sensitivity does not depend on the mass of the imaged atoms. The photoinduced ring opening of the heterocyclic molecule 2(5H)-thiophenone has attracted recent interest. Here, we show that CEI offers a powerful route to imaging the peripheral H atoms in this molecule and thus, more generally, to tracking detailed nuclear motions (e.g., isomerizations) in organic molecules on ultrafast time scales. Specifically, we record momentum-space Coulomb explosion images that report on the three-dimensional positioning of all nuclei within the molecule, for instance, distinguishing H atoms in C–H bonds that lie within or are directed out of the plane defined by the heavy atoms. The prospect of imaging peripheral H atoms to probe photochemical dynamics is explored by coupling ab initio molecular dynamics with classical Coulomb explosion simulations, thereby differentiating potential photoproduct isomers, including those whose structures primarily differ in the position of the hydrogens.
#RobSelects paper of the week #J_A_C_S: Detailed investigation of the methyl lactate van der Waals dimers via jet-cooled rotational spectroscopy. #physchem https://doi.org/10.1021/jacs.5c01184
#RobSelects preprint of the week #ChemRxiv: The N-iodo Hammick intermediate of reacts as a carbene via cleavage of the nitrogen-iodine bond. #physchem https://doi.org/10.26434/chemrxiv-2025-bf6qk
Hydrogen activation by a σσ*-carbene through quantum tunneling
The electronic structure of carbenes arises from the occupation of a σ and a π frontier orbital. While parent methylene possesses a triplet ground state (σ1π1), substituents are capable of stabilizing the singlet (σ2π0 or σ0π2) by altering the frontier orbital energies. Here, we reveal that the 1,2[I]-shift isomer of 2-iodopyridine, the N-iodo Hammick intermediate, features a resonance between its carbene σ and N–I bond σ* orbitals, rendering them frontier orbitals. This singlet carbene is efficiently generated via UV photolysis of 2-iodopyridine in solid neon at 4.4 K and reacts with molecular hydrogen − but not deuterium − via N–I bond cleavage enabled by quantum tunnelling. Our findings introduce an unprecedented carbene class, unlocking new opportunities for reactivity and electronic structure explorations.
#RobSelects paper of the week #ACSCatalysis: Systematic framework for reconciling kinetic information extracted from cyclic voltammetry to computed Gibbs free energy profiles of catalytic reactions. #physchem https://doi.org/10.1021/acscatal.4c06976
#RobSelects paper of the week #ScienceMagazine: Inducing chirality in boron phosphate with terahertz-frequency excitation pulses. #physchem https://doi.org/10.1126/science.adr4713
Fabio ColasuonnoI am excited to announce that our last work is on the interaction of Ru nanoparticle edge facets with hydrogen and butane for the investigation of alkanes hydrogenolysis reactivity is finally online as preprint on ChemRxiv - https://doi.org/10.26434/chemrxiv-2025-x59s5?utm_campaign=shareaholic&utm_medium=mastodon&utm_source=socialnetwork
#compchem #catalysis #physchem #ruthenium #modelling #DFT #ChemicalKinetics
Computational Insights into Hydrogen Interaction with the Ru (101 ̅1) and Ru (101 ̅0) Surfaces: Implications for Alkane and Polyolefin Hydrogenolysis
Hydrogen interaction with transition metal surfaces such as those exposed by ruthenium (Ru) nanoparticles is critical in applications like hydrogen storage and catalytic processes such as Fischer-Tropsch, Haber-Bosch, and plastic waste hydrogenolysis. While the Ru (0001) surface is well-studied, hydrogen interaction with the Ru (101 ̅1) and Ru (101 ̅0) facets remains mostly underexplored. In this contribution, we use density functional theory calculations to investigate hydrogen adsorption and dissociation and provide insights into the adsorbed hydrogen role in catalytic polyolefin plastic hydrogenolysis. We start our investigation by exploring all the unique surface and subsurface sites for hydrogen adsorption and dissociation and identify hcp and higher hollow as the most favorable atomic hydrogens adsorption sites on the Ru (101 ̅1) and Ru (101 ̅0) surfaces, respectively. We find that atomic hydrogen can easily migrate on these surfaces to achieve the most stable arrangement at different coverages. We then combine these findings with ab-initio thermodynamics and microkinetic modeling to build surface phase diagrams, which show that both surfaces are fully hydrogenated under typical catalytic conditions. We then study how the presence of the full hydrogen coverage affects the adsorption and dehydrogenation of butane as a proxy for polyethylene, as these are the initial steps in the catalytic hydrogenolysis of polyolefin plastic waste. We find that the adsorption energy of butane decreases when the two surfaces are fully hydrogenated but adsorption remains favorable. We then investigate two possible mechanisms for the dehydrogenation step. The most favorable dehydrogenation mechanism involves the reaction of a surface hydrogen with an alkane hydrogen to produce H2 gas and an adsorbed alkyl radical. However, both mechanisms have positive reaction free energies suggesting that polyolefin dehydrogenation will be slow on these surfaces.
ChemistryViewsUnderstanding Carbonic Acid Vibrations
Using advanced calculations to create a detailed model of H2CO3's vibrations, new spectral features were identified and previous uncertainties resolved, simplifying its detection in complex environments
https://www.chemistryviews.org/understanding-carbonic-acid-vibrations/
#RobSelects paper of the week #J_A_C_S: Experimental determination of valence electron density distributions in crystals via synchrotron x-ray radiation. #physchem https://doi.org/10.1021/jacs.4c05673
#RobSelects preprint of the week #ChemRxiv: Developing computer vision methods for parallel reaction monitoring. #physchem https://doi.org/10.26434/chemrxiv-2024-n1928
High Throughput Parallel Reaction Monitoring with Computer Vision
We report the development and applications of a computer vision based reaction monitoring method for high throughput experimentation (HTE). Whereas previous efforts reported methods to extract bulk kinetics from a single video, this new approach enables one video to capture bulk kinetics of multiple reactions running in parallel. Case studies in and beyond well-plate high throughput settings are described. Analysis of parallel dye-quenching hydroxylations, DMAP-catalysed esterification, solid-liquid sedimentation dynamics, metal catalyst degradation, and biologically-relevant sugar-mediated nitro reduction reactions have each provided insight into the scope and limitations of camera-enabled high throughput kinetics as a means of widening known analytical bottlenecks in HTE for reaction discovery, mechanistic understanding, and optimisation. It is envisaged that the nature of the multi-reaction time-resolved datasets made available by this analytical approach will later serve a broad range of downstream efforts in machine learning approaches towards exploring chemical space.