Theoretical investigation of CH-bond activation by photocatalytic excited SO2 and the effects of C-, N-, S-, and Se-doped TiO2

Condensed Matter Systems Exposed to Radiation: Multiscale Theory, Simulations, and Experiment

This roadmap reviews the new, highly interdisciplinary research field studying the behavior of condensed matter systems exposed to radiation. The Review highlights several recent advances in the field and provides a roadmap for the development of the field over the next decade. Condensed matter systems exposed to radiation can be inorganic, organic, or biological, finite or infinite, composed of different molecular species or materials, exist in different phases, and operate under different thermodynamic conditions. Many of the key phenomena related to the behavior of irradiated systems are very similar and can be understood based on the same fundamental theoretical principles and computational approaches. The multiscale nature of such phenomena requires the quantitative description of the radiation-induced effects occurring at different spatial and temporal scales, ranging from the atomic to the macroscopic, and the interlinks between such descriptions. The multiscale nature of the effects and the similarity of their manifestation in systems of different origins necessarily bring together different disciplines, such as physics, chemistry, biology, materials science, nanoscience, and biomedical research, demonstrating the numerous interlinks and commonalities between them. This research field is highly relevant to many novel and emerging technologies and medical applications.

Importance of Polarizable Embedding for Absorption Spectrum Calculations of Arabidopsis thaliana Cryptochrome 1

Cryptochromes are essential flavoproteins for circadian rhythms and avian magnetoreception. Flavin adenine dinucleotide (FAD), a chromophore within cryptochromes, absorbs blue light, initiating electron transfer processes that lead to a biological signaling cascade. A key step in this cascade is the formation of the FAD semiquinone radical (FADH•), characterized through a specific red-light absorption. The absorption spectra of FADH• in cryptochromes are, however, significantly different from those recorded for the cofactor in solution, primarily due to protein-induced shifts in the absorption peaks. This study employs a multiscale approach, combining molecular dynamics (MD) simulations with quantum mechanical/molecular mechanical (QM/MM) methodologies, to investigate the influence of protein dynamics on embedded FADH• absorption. We emphasize the role of the protein's polarizable environment in the shaping of the absorption spectrum, crucial for accurate spectral predictions in cryptochromes. Our findings provide valuable insights into the absorption process, advancing our understanding of cryptochrome functioning.

Peculiar Differences between Two Copper Complexes Containing Similar Redox-Active Ligands: Density Functional and Multiconfigurational Calculations

Transition metal complexes featuring redox-active ligands often exhibit multiple redox states, influenced by the interplay between the metal center and the ligand. This study delves into the electronic structures of two mononuclear complexes of copper with two similar redox-active urea azine ligands. The ligands differ by the replacement of an NCH3 moiety by an S atom in the ligand backbone. Experimental analysis yields pronounced electronic structural disparities between these complexes, observable in both the solution and solid phases. Conventional quantum chemical methods, such as density functional theory using different functionals (B3LYP, TPSSh, and CAM-B3LYP), remain inadequate to rationalize the observed spectroscopic anomalies. However, a multiconfigurational approach elucidates the disparate behaviors of these complexes. Multireference perturbation theory, based on complete active space self-consistent field computations, identifies Cu(I) in the case of the complex with the NCH3 containing ligands and a state with substantial Cu(II) contributions in the case of the complex with the S atom containing ligands. In contrast, DFT indicates Cu(I) in both scenarios.

New Insights on Singlet Oxygen Release from Li-Air Battery Cathode: Periodic DFT Versus CASPT2 Embedded Cluster Calculations

Li-air batteries are a promising energy storage technology for large-scale applications, but the release of highly reactive singlet oxygen (1O2) during battery operation represents a main concern that sensibly limits their effective deployment. An in-depth understanding of the reaction mechanisms underlying the 1O2 formation is crucial to prevent its detrimental reactions with the electrolyte species. However, describing the elusive chemistry of highly correlated species such as singlet oxygen represents a challenging task for state-of-the-art theoretical tools based on density functional theory. Thus, in this study, we apply an embedded cluster approach, based on CASPT2 and effective point charges, to address the evolution of 1O2 at the Li2O2 surface during oxidation, i.e., the battery charging process. Based on recent hypothesis, we depict a feasible O22-/O2-/O2 mechanisms occurring from the (112̅0)-Li2O2 surface termination. Our highly accurate calculations allow for the identification of a stable superoxide as local minimum along the potential energy surface (PES) for 1O2 release, which is not detected by periodic DFT. We find that 1O2 release proceeds via a superoxide intermediate in a two-step one-electron process or another still accessible pathway featuring a one-step two-electron mechanism. In both cases, it represents a feasible product of Li2O2 oxidation upon battery charging. Thus, tuning the relative stability of the intermediate superoxide species can enable key strategies aiming at controlling the detrimental development of 1O2 for new and highly performing Li-air batteries.