Electronic Structure and Geometry of the Lowest 2LMCT State of Fe(III) Potential Fluorescent Emitters†.

Metal complexes with a 3d6 electron count are emerging as an alternative to 4d6-based photosensitizers, emitters, or photoredox catalysts. In recent years, several Fe(II) potential emitters have been proposed, based on strongly donating ligand sets. Those tend to facilitate oxidation to their 3d5 species, whose photophysics is based on low-lying ligand-to-metal charge-transfer (LMCT) states. The geometry and electronic structure of 2LMCT states are unveiled in this work.

Tackling Structural Complexity in Li2S-P2S5 Solid-State Electrolytes Using Machine Learning Potentials.

The lithium thiophosphate (LPS) material class provides promising candidates for solid-state electrolytes (SSEs) in lithium ion batteries due to high lithium ion conductivities, non-critical elements, and low material cost. LPS materials are characterized by complex thiophosphate microchemistry and structural disorder influencing the material performance. To overcome the length and time scale restrictions of ab initio calculations to industrially applicable LPS materials, we develop a near-universal machine-learning interatomic potential for the LPS material class. The trained Gaussian Approximation Potential (GAP) can likewise describe crystal and glassy materials and different P-S connectivities PmSn. We apply the GAP surrogate model to probe lithium ion conductivity and the influence of thiophosphate subunits on the latter. The materials studied are crystals (modifications of Li3PS4 and Li7P3S11), and glasses of the xLi2S-(100 - x)P2S5 type (x = 67, 70 and 75). The obtained material properties are well aligned with experimental findings and we underscore the role of anion dynamics on lithium ion conductivity in glassy LPS. The GAP surrogate approach allows for a variety of extensions and transferability to other SSEs.

Effect of Hydration on Electron Attachment to Methanesulfonic Acid Clusters.

We report an experimental and computational study of the electron-induced chemistry of methanesulfonic acid (MSA, MeSO3H) in clusters. We combine the mass spectra after the 70 eV electron ionization with the negative ion spectra after electron attachment (EA) at low electron energies of 0-15 eV of the MSA molecule, small MSA clusters, and microhydrated MSA clusters to reveal the solvation effects. The MSA/He coexpansion only generates small MSA clusters with up to four molecules, but adding water substantially hydrates the MSA clusters, resulting in clusters composed of 1-2 MSA molecules accompanied by quite a few water molecules. The clustering strongly suppresses the fragmentation of the MSA molecules upon both the positive ionization and EA. The electron-energy-dependent ion yield for different negative ions is measured. For the MSA molecule and pure MSA clusters, EA leads to an H-abstraction yielding MeSO3-. It proceeds efficiently at low electron energies below 2 eV with a shoulder at 3-4 eV and a broad, almost 2 orders of magnitude weaker, peak around 8 eV. The hydrated (H2O)nMeSO3- ions with n ≤ 3 exhibit only a broad peak around 7 eV similar to EA of pure water clusters. Thus, for the small clusters, the electron attachment and hydrogen abstraction from water occur. On the other hand, the larger clusters with n > 4 display a peak below 2 eV, which quickly dominates the spectrum with increasing n. This peak is related to the formation of the H3O+·MeSO3- ion pair upon hydration and subsequent dipole-supported electron attachment followed by the hydronium neutralization and H3O• radical dissociation. The size-resolved experimental data indicate that the ionic dissociation of MSA starts to occur in the neutral MeSO3H(H2O)N clusters with about four water molecules.

Parasitic behavior in competing chemically fueled reaction cycles.

Non-equilibrium, fuel-driven reaction cycles serve as model systems of the intricate reaction networks of life. Rich and dynamic behavior is observed when reaction cycles regulate assembly processes, such as phase separation. However, it remains unclear how the interplay between multiple reaction cycles affects the success of emergent assemblies. To tackle this question, we created a library of molecules that compete for a common fuel that transiently activates products. Often, the competition for fuel implies that a competitor decreases the lifetime of these products. However, in cases where the transient competitor product can phase-separate, such a competitor can increase the survival time of one product. Moreover, in the presence of oscillatory fueling, the same mechanism reduces variations in the product concentration while the concentration variations of the competitor product are enhanced. Like a parasite, the product benefits from the protection of the host against deactivation and increases its robustness against fuel variations at the expense of the robustness of the host. Such a parasitic behavior in multiple fuel-driven reaction cycles represents a lifelike trait, paving the way for the bottom-up design of synthetic life.