Geometries, electronic structures, and bonding properties of endohedral Group-14 Zintl clusters TM@E10 (TM = Fe, Co, Ni; E = Ge, Sn, Pb).

The geometries, electronic structures, and bonding properties of the title endohedral Zintl clusters have been studied by using ab initio calculations. [Fe@Ge10 ]4- and [Co@Ge10 ]3- have D5h -symmetric pentagonal prismatic structure and [Fe@Sn10 ]4- adopts the C2v -symmetric structure as their ground-state structures, whereas all the other clusters possess D4d bicapped square antiprismatic structures, in consistent with the experimental values when available. Natural bonding orbital and electron localization function disclosed that the negative charges are localized on the central atoms rather than the cages while the TME ionic bonding interactions increase in the order of Ge < Sn < Pb. The energy decomposition analysis revealed that the total bonding energy ∆Eint between central TM and E10 cage is above 150 kcal/mol. The ionic bonding interaction termed as electrostatic interaction ∆Eelstat increases in the order of Ge < Sn < Pb and becomes higher than the covalent bonding interactions termed as total orbital interactions ∆Eorb . Among the total orbital interactions, the π back donations from the TM-d orbitals to the empty cage orbitals consisting of E-p orbitals, the magnitude of which is importantly affected by the cage symmetry, are dominant contributions.

Stable Noble Gas Compounds Based on Superelectrophilic Anions [B12 (BO)11 ]- and [B12 (OBO)11 ].

Superelectrophilic monoanions [B12 (BO)11 ]- and [B12 (OBO)11 ]- , generated from stable dianions [B12 (BO)12 ]2- and [B12 (OBO)12 ]2- , show great potential for binding with noble gases (Ngs). The binding energies, quantum theory of atoms in molecules (QTAIM), natural population analysis (NPA), energy decomposition analysis (EDA), and electron localization function (ELF) were carried out to understand the B-Ng bond in [B12 (BO)11 Ng]- and [B12 (OBO)11 Ng]- . The calculated results reveal that heavier noble gases (Ar, Kr, and Xe) bind covalently with both [B12 (BO)11 ]- and [B12 (OBO)11 ]- with large binding energies, making them potentially feasible to be synthesized. Only [B12 (OBO)11 ]- could form a covalent bond with helium or neon but the small binding energy of [B12 (OBO)11 He]- may pose a challenge for its experimental detection.

Endohedral group-14-element clusters TM@E9 (TM = Co, Ni, Cu; E = Ge, Sn, Pb) and their low-dimensional nanostructures: a first-principles study.

Endohedral group14-based clusters with the encapsulation of a transition metal, which are termed [TM@Em]n- (TM = transition metal and E = group-14 elements), have lots of potential applications and have been used as interesting building blocks in materials science. Nevertheless, their electronic structures and stability mechanism remain unclear. In this paper, we systematically study the geometries, electronic structures, and bonding properties of [TM@E9]n- clusters which are the smallest endohedral group-14-based clusters synthesized so far, by using density functional theory (DFT) calculations. The calculation results reveal the important role of TMs in affecting the structures and bonding interactions in the [TM@E9]n- cluster. In the presence of a TM, the cluster geometry could change from a monocapped square antiprism (C4v) for empty [E9]4- cages to a tricapped trigonal prismatic geometry (D3h) for [TM@E9]n-. By using the energy decomposition analysis (EDA) method, the bonding properties between the endohedral TM and E9 cluster have been thoroughly investigated. It was found that the origin of stability of these clusters is from the large electrostatic attraction with significantly reduced Pauli repulsion. In the case of orbital interactions, the π back-donations from d orbitals of the TM to the cluster make important contributions. More interestingly, the 1D-chain and 2D-sheet nanostructures based on the [Ni@E9] cluster have been theoretically predicted. The band structure and density of states analysis revealed that all of these nanostructures are metallic and their excellent thermodynamic stability has been confirmed by using ab initio molecular dynamics (AIMD) simulations.

Stabilities, Electronic Structures, and Bonding Properties of 20-Electron Transition Metal Complexes (Cp)2TMO and their One-Dimensional Sandwich Molecular Wires (Cp = C5H5, C5(CH3)H4, C5(CH3)5; TM = Cr, Mo, W).

First-principles calculations have been carried out for the 20-electron transition metal complexes (Cp)2TMO and their molecular wires (Cp = C5H5, C5(CH3)H4, C5(CH3)5; TM = Cr, Mo, W). The calculation results at the BP86/def2-TZVPP level reveal that the ground state is singlet and the optimized geometries are in good agreement with the experimental values. The analysis of frontier molecular orbitals shows that two electrons in the highest occupied molecular orbital HOMO-1 are mainly localized on cyclopentadienyl and oxygen ligands. Furthermore, the nature of the TM-O bond was investigated with the energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV). The attraction term in the intrinsic interaction energies ΔEint is mainly composed of two important parts, including electrostatic interaction (about 52% of the total attractive interactions ΔEelstat + ΔEorb) and orbital interaction, which might be the major determinant of the stability of these (Cp)2TMO complexes. All of the TM-O bonds should be described as electron-sharing σ single bonds [(Cp)2TM]+-[O]- with the contribution of 53-57% of ΔEorb and two π backdonations from the occupied p orbitals of oxygen ligands into vacant π* MOs of the [(Cp)2TM]+ fragments, which are 35-40% of ΔEorb. The results of bond order and interaction energy from EDA-NOCV calculations suggest the influence of the radius of TM and methyl in the interactions between TM and O in (Cp)2TMO. Additionally, the relativistic effects slightly amplify the strength of bonding with increasing ΔEorb for the EDA-NOCV calculations on three metal complexes (C5H5)2TMO. Finally, the geometries, electronic structures, and magnetics of infinitely extended systems, [(C5H5)TMO]∞, have also been explored. The results of the density of states (DOS) and band structure revealed that [(C5H5)CrO]∞ and [(C5H5)WO]∞ are semiconductors with the narrow bands, whereas [(C5H5)MoO]∞ behaves as metal.

[Strategies for infection control in managing critically ill patients with suspected coronavirus disease 2019 in non-designated hospital].

The management of healthcare services for the suspected cases in non-designated hospitalsis a serious concern in controlling coronavirus disease 2019 (COVID-19) epidemic. Owing to the complexity of care providers, large requirement of medical supplies as well as the possible needs off frequent transfers, the major difficulty is preventing the coronavirus from spreading while caring the suspected critical cases before the 2019 novel coronavirus ribonucleic acid test results are reported. For the purpose of enhancing the prevention of the propagation of COVID-19, this article puts emphasis on the following aspects in non-designated hospital Peking University Third Hospital: preparatory procedures of receiving critical suspected patients, the management of medical personnel during the waiting session of RNA test results, the delivering procedures of testing samples, the management of referred medical wastes, daily operations including the cleaning and sanitizing of caring units and the management of related patients after the testing session.

Stabilities, Electronic Structures, and Bonding Properties of Iron Complexes (E1E2)Fe(CO)2(CNArTripp2)2 (E1E2=BF, CO, N2, CN-, or NO+).

The coordination of 10-electron diatomic ligands (BF, CO N2) to iron complexes Fe(CO)2(CNArTripp2)2 [ArTripp2=2,6-(2,4,6-(iso-propyl)3C6H2)2C6H3] have been realized in experiments very recently (Science, 2019, 363, 1203-1205). Herein, the stability, electronic structures, and bonding properties of (E1E2)Fe-(CO)2(CNArTripp2)2 (E1E2=BF, CO, N2, CN-, NO+) were studied using density functional (DFT) calculations. The ground state of all those molecules is singlet and the calculated geometries are in excellent agreement with the experimental values. The natural bond orbital analysis revealed that Fe is negatively charged while E1 possesses positive charges. By employing the energy decomposition analysis, the bonding nature of the E2E1-Fe(CO)2(CNArTripp2)2 bond was disclosed to be the classic dative bond E2E1→Fe(CO)2(CNArTripp2)2 rather than the electron-sharing double bond. More interestingly, the bonding strength between BF and Fe(CO)2(CNArTripp2)2 is much stronger than that between CO (or N2) and Fe(CO)2(CNArTripp2)2, which is ascribed to the better σ-donation and π back-donations. However, the orbital interactions in CN-→Fe(CO)2(CNArTripp2)2 and NO+→Fe(CO)2(CNArTripp2)2 mainly come from σ-donation and π back-donation, respectively. The different contributions from σ donation and π donation for different ligands can be well explained by using the energy levels of E1E2 and Fe(CO)2(CNArTripp2)2 fragments.

Strong metal-support interaction promoted scalable production of thermally stable single-atom catalysts.

Single-atom catalysts (SACs) have demonstrated superior catalytic performance in numerous heterogeneous reactions. However, producing thermally stable SACs, especially in a simple and scalable way, remains a formidable challenge. Here, we report the synthesis of Ru SACs from commercial RuO2 powders by physical mixing of sub-micron RuO2 aggregates with a MgAl1.2Fe0.8O4 spinel. Atomically dispersed Ru is confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption spectroscopy. Detailed studies reveal that the dispersion process does not arise from a gas atom trapping mechanism, but rather from anti-Ostwald ripening promoted by a strong covalent metal-support interaction. This synthetic strategy is simple and amenable to the large-scale manufacture of thermally stable SACs for industrial applications.

Association of Habitually Low Intake of Dietary Calcium with Blood Pressure and Hypertension in a Population with Predominantly Plant-Based Diets.

This study aimed to assess the association of habitually low dietary calcium intake with blood pressure or hypertensive risk using data from the China Health and Nutrition Survey (CHNS) in 2009. We included 6298 participants (2890 men and 3408 women) aged 18 years or older in this analysis. Food intakes were measured by 3-day 24-h individual recalls combined with a weighing and measuring of household food inventory. The participants were divided into normotensive, pre-hypertensive and hypertensive groups according to their mean blood pressure of three repeated measurements. Six intake levels were decided by percentiles of gender-specific dietary calcium intakes (P0⁻10, P10⁻30, P30⁻50, P50⁻70, P70⁻90, and P90⁻100). Average dietary calcium intakes were 405 mg/day for men and 370 mg/day for women, 80% and 84% of which were derived from plant-based food in men and women, respectively. Multiple linear regression analyses showed that dietary calcium intakes were not related with blood pressure in both genders (all P > 0.05). Logistic regression analyses showed a lower risk of pre-hypertension with higher dietary calcium intakes in women (all Pfor trend < 0.001), but not in men; no association between dietary calcium intake and hypertensive risk was found in both genders (all Pfor trend > 0.05). This study suggests that there are no conclusive associations of habitually low dietary calcium intake with blood pressure or hypertensive risk in Chinese individuals consuming predominantly plant-based diets.