Anthropogenic mercury (Hg(0)) emissions oxidize to gaseous Hg(II) compounds, before deposition to Earth surface ecosystems. Atmospheric reduction of Hg(II) competes with deposition, thereby modifying the magnitude and pattern of Hg deposition. Global Hg models have postulated that Hg(II) reduction in the atmosphere occurs through aqueous-phase photoreduction that may take place in clouds. Here we report that experimental rainfall Hg(II) photoreduction rates are much slower than modelled rates. We compute absorption cross sections of Hg(II) compounds and show that fast gas-phase Hg(II) photolysis can dominate atmospheric mercury reduction and lead to a substantial increase in the modelled, global atmospheric Hg lifetime by a factor two. Models with Hg(II) photolysis show enhanced Hg(0) deposition to land, which may prolong recovery of aquatic ecosystems long after Hg emissions are lowered, due to the longer residence time of Hg in soils compared with the ocean. Fast Hg(II) photolysis substantially changes atmospheric Hg dynamics and requires further assessment at regional and local scales.

The electronic-structure properties of the low-lying electronic states and the absorption cross sections of mercury halides have been determined within the UV-vis spectrum range (170 nm ≤ λphoton ≤ 600 nm).

Frustrated Lewis pairs (FLPs) based on nitrogen heterocycles (pyridine, pyrazole, and imidazole) with a silane or germane group in the α-position of a nitrogen atom have been considered as potential molecules to sequestrate carbon dioxide. Three stationary points have been characterized in the reaction profile: a pre-reactive complex, an adduct minimum, and the transition state connecting them. The effect of external (solvent) or internal (hydroxyl group) electric fields in the reaction profile has been considered. In both cases, it is possible to improve the kinetics and thermodynamics of the complexation of CO 2 by the FLP and favor the formation of adducts.

Diborane has long been realized to be analogous to ethylene in terms of its bonding MOs, both as to symmetries and splitting patterns. This naturally suggests an investigation to see whether other similar conjugated hydrocarbons manifest a similar boron‐substituted and H2 supplemented borane. That is, for a conjugated hydrocarbon structure with a neighbor‐paired resonance pattern, we propose to look at boranes where each carbon atom is replaced by a boron atom, and an H‐atom pair is added to each double bond of the resonance structure, with one H above the molecular plane and one below. This construction of concatenated diboranes is uniformly different than that for the previously known stable boranes of 4 or more B atoms. We find from quantum‐chemical computations that our so constructed polyboranes are stable. All this suggests a possible novel new chapter in borane chemistry – a chapter with some promise of understandings related to that for (alternant) conjugated hydrocarbons.

The weakly coordinating binary macropolyhedral anion closo,closo- [B 21 H 18 ]À (B21; D 3h symmetry) has been synthesized using a simplified strategy compared to that in the literature. While gas-phase complexes of B21 with b-and c-cyclodextrin (CD) were detected using ESI FT-ICR spectrometric measurements, a-CD did not bind to the B21 guest. This spectroscopic evidence has been interpreted using quantum-chemical

A theoretical study of the hydrogen bond (HB) and halogen bond (XB) complexes between 1-halo-closo-carboranes and hydrogen cyanide (NCH) as HB and XB probe has been carried out at the MP2 computational level. The energy results show that the HB complexes are more stable than the XBs for the same system, with the exception of the isoenergetic iodine derivatives. The analysis of the electron density with the quantum theory of atoms in molecules (QTAIM) shows the presence of a unique intermolecular bond critical point with the typical features of weak noncovalent interactions (small values of the electron density and positive Laplacian and total energy density). The natural energy decomposition analysis (NEDA) of the complexes shows that the HB and XB complexes are dominated by the charge-transfer and polarization terms, respectively. The work has been complemented with a search in the CSD database of analogous complexes and the comparison of the results, with those of the 1-halobenzene:NCH complexes showing smaller binding energies and larger intermolecular distances as compared to the 1-halo-closo-carboranes:NCH complexes.

We analyze the magnetic properties of three mononuclear Co(II) coordination complexes using quantum chemical complete active space self-consistent field and N-electron valence perturbation theory approaches. The complexes are characterized by a distorted tetrahedral geometry in which the central ion is doubly chelated by the icosahedral ligands derived from 1,2-(HS)-1,2-CBH (complex I), from 1,2-(HS)-1,2-CBH and 9,12-(HS)-1,2-CBH (complex II), and from 9,12-(HS)-1,2-CBH (complex III), which are two positional isomers of dithiolated 1,2-dicarba- closo-dodecaborane (complex I). Complex I was realized experimentally recently (Tu, D.; Shao, D.; Yan, H.; Lu, C. Chem. Commun. 2016, 52, 14326) and served to validate the computational protocol employed in this work, while the remaining two proposed complexes can be considered positional isomers of I. Our calculations show that these complexes present different axial and rhombic zero-field splitting anisotropy parameters and different values of the most significant components of the g tensor. The predicted axial anisotropy D = -147.2 cm for complex II is twice that observed experimentally for complex I, D = -72.8 cm, suggesting that this complex may be of interest for practical applications. We also analyze the temperature dependence of the magnetic susceptibility and molar magnetization for these complexes when subject to an external magnetic field. Overall, our results suggest that o-carborane-incorporated Co(II) complexes are worthwhile candidates for experimental exploration as single-ion molecular magnets.

By following the intrinsic reaction coordinate connecting transition states with energy minima on the potential energy surface, we have determined the reaction steps connecting three-dimensional hexaborane(12) with unknown planar two-dimensional hexaborane(12). In an effort to predict the potential synthesis of finite planar borane molecules, we found that the reaction limiting factor stems from the breaking of the central boron-boron bond perpendicular to the C2 axis of rotation in three-dimensional hexaborane(12).