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The premise of most studies on the homogeneous electrocatalytic CO 2 reduction reaction (CO 2 RR) is a good understanding of the reaction mechanisms. Yet, analyzing the reaction intermediates formed at the working electrode is challenging and not always attainable. Here, we present a new, general approach to studying the reaction intermediates applied for CO 2 RR catalyzed by a series of cobalt complexes. The cobalt complexes were based on the TPA-ligands (TPA = tris(2-pyridylmethyl)amine) modified by amino groups in the secondary coordination sphere. By combining the electrochemical experiments, electrochemistry-coupled electrospray ionization mass spectrometry, with density functional theory (DFT) calculations, we identify and spectroscopically characterize the key reaction intermediates in the CO 2 RR and the competing hydrogen-evolution reaction (HER). Additionally, the experiments revealed the rarely reported in situ changes in the secondary coordination sphere of the cobalt complexes by the CO 2 -initiated transformation of the amino substituents to carbamates. This launched an even faster alternative HER pathway. The interplay of three catalytic cycles, as derived from the experiments and supported by the DFT calculations, explains the trends that cobalt complexes exhibit during the CO 2 RR and HER. Additionally, this study demonstrates the need for a molecular perspective in the electrocatalytic activation of small molecules efficiently obtained by the EC-ESI-MS technique.

The stereoisomeric system of rac -2-phenylglycinamide (PGA) and rac - N -acetyl tryptophan (NAT) is significant in the application of chiral resolution because it has been shown that this system can be used for enantioseparation of PGA and/or NAT using a novel deracemization route of the conglomerate salt formed. However, it was also found that the conglomerate salt eventually converted into different crystal forms that limited the time available for the separation. Herein, we try to understand the phase conversion occurring in this system using DSC, PXRD, and SC-XRD. The related structures of the salt (two polymorphs of the more stable homochiral (dd- and ll-) salts and one polymorph of the less stable heterochiral (dl- and ld-) monohydrate salts) are demonstrated and discussed relating to their relative stabilities. The successful deracemization was demonstrated using the heterochiral (dl- or ld-) monohydrate salts. However, following Ostwald's rule of stages, only limited time is available for the deracemization before the metastable compound converts into the more stable homochiral (dd- and ll-) pair. Moreover, the occurrence of the (dd- and ll-) phase always coincides with the formation of yet another phase of the racemic compound containing four components in a crystal. Ostwald's rule of stages here thus involves three steps and phases and is highly significant during the deracemization of the homochiral species., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Recent developments in the field of high efficiency perovskite solar cells are based on stabilization of the perovskite crystal structure of FAPbI 3 while preserving its excellent optoelectronic properties. Compositional engineering of, for example, MA or Br mixed into FAPbI 3 results in the desired effects, but detailed knowledge of local structural features, such as local (dis)order or cation interactions of formamidinium (FA) and methylammonium (MA), is still limited. This knowledge is, however, crucial for their further development. Here, we shed light on the microscopic distribution of MA and FA in mixed perovskites MA 1- x FA x PbI 3 and MA 0.15 FA 0.85 PbI 2.55 Br 0.45 by combining high-resolution double-quantum 1 H solid-state nuclear magnetic resonance (NMR) spectroscopy with state-of-the-art near-first-principles accuracy molecular dynamics (MD) simulations using machine-learning force-fields (MLFFs). We show that on a small local scale, partial MA and FA clustering takes place over the whole MA/FA compositional range. A reasonable driving force for the clustering might be an increase of the dynamical freedom of FA cations in FA-rich regions. While MA 0.15 FA 0.85 PbI 2.55 Br 0.45 displays similar MA and FA ordering as the MA 1- x FA x PbI 3 systems, the average cation-cation interaction strength increased significantly in this double mixed material, indicating a restriction of the space accessible to the cations or their partial immobilization upon Br - incorporation. Our results shed light on the heterogeneities in cation composition of mixed halide perovskites, helping to exploit their full optoelectronic potential., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Although it is well established that the acidity of phenol can be fine-tuned with substituents on its aromatic ring via through-bond effects, the role of through-space effects on the acidity of phenols is presently poorly understood. Here, we present integrated experimental and computational studies on substituted 2,6-diarylphenols that demonstrate the essential contribution from through-space OH-π interactions and O - -π interactions in the observed trends in proton affinities and acidities of 2,6-diarylphenols.

Energetically favorable cation-π interactions play important roles in numerous molecular recognition processes in chemistry and biology. Herein, we present synergistic experimental and computational physical-organic chemistry studies on 2,6-diarylanilines that contain flanking meta/para-substituted aromatic rings adjacent to the central anilinium ion. A combination of measurements of pK a values, structural analyses of 2,6-diarylanilinium cations, and quantum chemical analyses based on the quantitative molecular orbital theory and a canonical energy decomposition analysis (EDA) scheme reveal that through-space cation-π interactions essentially contribute to observed trends in proton affinities and pK a values of 2,6-diarylanilines.