Encaged molecules in external electric fields: A molecular "tug-of-war"

Multivariate covalent organic frameworks with tailored electrostatic potential promote nitrate electroreduction to ammonia in acid

The direct synthesis of ammonia from nitrate (NO3-) reduction in acid is a promising approach for industrialization. However, the difficulty arises from the intense competition with the inevitable hydrogen evolution reaction, which is favoured due to the overwhelming protons (H+). Here, we systematically explore and rationally optimize the microenvironment using multivariate covalent organic frameworks (COFs) as catalyst adlayers to promote the nitrate-to-ammonia conversion in acid. With the application of tailored positive electrostatic potential generated over the multivariate COFs, both the mass transfer of NO3- and H+ are regulated via appropriate electrostatic interactions, thus realizing the priority of NO3RR with respect to HER or NO3--to-NO2-. As a result, an NH3 yield rate of 11.01 mmol h-1 mg-1 and a corresponding Faradaic efficiency of 91.0% are attained, and solid NH4Cl with a high purity of 96.2% is directly collected in acid; therefore, this method provides a practical approach for economically valorising wastewater into valuable ammonia.

Electromagnetic bioeffects: a multiscale molecular simulation perspective

Electromagnetic bioeffects remain an enigma from both the experimental and theoretical perspectives despite the ubiquitous presence of related technologies in contemporary life. Multiscale computational modelling can provide valuable insights into biochemical systems and predict how they will be perturbed by external stimuli. At a microscopic level, it can be used to determine what (sub)molecular scale reactions various stimuli might induce; at a macroscopic level, it can be used to examine how these changes affect dynamic behaviour of essential molecules within the crowded biomolecular milieu in living tissues. In this review, we summarise and evaluate recent computational studies that examined the impact of externally applied electric and electromagnetic fields on biologically relevant molecular systems. First, we briefly outline the various methodological approaches that have been employed to study static and oscillating field effects across different time and length scales. The practical value of such modelling is then illustrated through representative case-studies that showcase the diverse effects of electric and electromagnetic field on the main physiological solvent - water, and the essential biomolecules - DNA, proteins, lipids, as well as some novel biomedically relevant nanomaterials. The implications and relevance of the theoretical multiscale modelling to practical applications in therapeutic medicine are also discussed. Finally, we summarise ongoing challenges and potential opportunities for theoretical modelling to advance the current understanding of electromagnetic bioeffects for their modulation and/or beneficial exploitation in biomedicine and industry.

Hydration Shell Model for Expeditious and Reliable Individual Hydrogen Bond Energies in Large Water Clusters

Recently, we have developed and tested a method, based on the molecular tailoring approach (MTA-based) to directly estimate the individual hydrogen bond (HB) energies in molecular clusters. Application of this...

Rotatory Response of Molecular Electron Momentum Densities in Linear, Homogeneous Weak Electric Fields: A Topographical Analysis

One-electron properties for molecules such as electron density, electrostatic potential (ESP), and electron momentum density (EMD) are experimentally tractable quantities, useful in understanding chemical characteristics. In this work, effects of a uniform homogeneous external electric field on some characteristic one-electron properties of simple molecules are analyzed. EMDs and ESPs were used to understand the response of water, hydrogen fluoride, carbon monoxide, chloroacetylene, and ammonia in an electric field. Remarkably, the EMD maxima for these molecules get rotated as the electric field strength is varied. A greater order of change in EMD than in ESP with increasing electric field strength brings out the sensitivity of the EMDs, especially for the valence electronic region, which in the momentum space is mapped onto the vicinity of its origin. The eigenvectors of the EMD Hessian maxima at the momentum-space origin are seen to rotate as a function of increasing field strength, with the extra angular momentum imparted by the field manifesting itself as reconfiguration of the EMD distribution. In the presence of the field, valence states may couple with higher electronic states, leading to a mixing of the states resulting in avoided crossings as a function of the field strength. The avoided crossings legitimately estimate maximal field strength limits for the calculation, prior to ionization.

Advances in spectroscopy and dynamics of small and medium sized molecules and clusters

Investigations of the spectroscopy and dynamics of small- and medium-sized molecules and clusters represent a hot topic in atmospheric chemistry, biology, physics, atto- and femto-chemistry and astrophysics.