Synthesis and Characterization of η⁵-1,2,4-Diazaphospholide Complexes of Ruthenium^†

Treatment of the 1,2,4-diazaphospholide anions [3,5-tBu2dp]- (1) and [3,5-Ph2dp]- (2) with [Cp*RuCl]4 affords the two complexes [(η5-3,5-tBu2dp)RuCp*] (3) and [(η5-3,5-Ph2dp)RuCp*] (4) (dp = 1,2,4-diazaphospholide), which are the first examples of sandwich complexes derived from 1,2,4-diazaphospholide ligands. The X-ray crystal structure analysis of 3 reveals that the metal atom is π-bonded to the 1,2,4-diazaphospholide ligand. The bonding was rationalized by DFT calculations

Synthesis and Characterization of η⁵-1,2,4-Diazaphospholide Complexes of Ruthenium^†

Treatment of the 1,2,4-diazaphospholide anions [3,5-tBu2dp]- (1) and [3,5-Ph2dp]- (2) with [Cp*RuCl]4 affords the two complexes [(η5-3,5-tBu2dp)RuCp*] (3) and [(η5-3,5-Ph2dp)RuCp*] (4) (dp = 1,2,4-diazaphospholide), which are the first examples of sandwich complexes derived from 1,2,4-diazaphospholide ligands. The X-ray crystal structure analysis of 3 reveals that the metal atom is π-bonded to the 1,2,4-diazaphospholide ligand. The bonding was rationalized by DFT calculations

A First-Principle Study of Synergized O₂ Activation and CO Oxidation by Ag Nanoparticles on TiO₂(101) Support

We performed density functional theory (DFT) calculations to investigate the synergized O₂ activation and CO oxidation by Ag₈ cluster on TiO₂(101) support. The excellent catalytic activity of the interfacial Ag atoms in O₂ dissociation is ascribed to the positive polarized charges, upshift of Ag d-band center, and assistance of surface Ti_5c atoms. CO oxidation then takes place via a two-step mechanism coupled with O₂ dissociation: (i) CO + O₂ → CO₂ + O and (ii) CO + O → CO₂. The synergistic effect of CO and O₂ activations reduces the oxidation energy barrier (<i>E</i>_a) of reaction (i), especially for the up-layered Ag atoms not in contact with support. It is found that the coadsorbed CO and O₂ on the up-layered Ag atoms form a metal-stable four-center O–O–CO structure motif substantially promoting CO oxidation. On the oxygen defective Ag₈/TiO₂(101) surface, because of the decreased positive charges and the down-shift of d-band centers in Ag, the metal cluster exhibits low O₂ adsorption and activation abilities. Although the dissociation of O₂ is facilitated by the TiO₂(101) defect sites, the dissociated O atoms would cover the defects so strongly that further CO oxidation would be prohibited unless much extra energy is introduced to recreate oxygen defects

Table_1_Natural History of Anal Papillomavirus Infection in HIV-Negative Men Who Have Sex With Men Based on a Markov Model: A 5-Year Prospective Cohort Study.DOCX

ObjectiveMen who have sex with men (MSM) are at increased risk for Human papillomavirus (HPV) infection compared to women and heterosexual men. We aimed to assess the incidence, clearance and duration of anal human papillomavirus (HPV) infection in HIV-negative MSM and the influencing factors in a 5-year prospective cohort study.MethodsFrom April 2016 to April 2021, HIV-negative MSM were recruited and followed every 6 months in Urumqi, Xinjiang, China. Questionnaires and anal swabs were collected at baseline and every 6 months. We detected 37 anal HPV genotypes using the HPV Geno Array Diagnostic Kit Test. Incidence and clearance rates of anal HPV infection and the influencing factors were estimated using a two-state Markov model.ResultsA total of 585 MSM were included with a median age of 37 years [interquartile range (IQR): 31–43 years] and were followed for a median 2.8 years (IQR: 1.8–3.6 years). Incidence rates for any HPV and high-risk HPV (Hr-HPV) were 53.4 [95% confidence interval (CI): 49.1–58.0] and 39.0 (95% CI: 35.7–42.5)/1,000 person-months. Median duration of infection was 9.67 (95% CI: 8.67–10.86) and 8.51 (95% CI: 7.57–9.50) months, respectively. Clearance rates for any HPV and Hr-HPV were 50.9 (95% CI: 46.7–55.3) and 62.1 (95% CI: 56.8–66.7)/1,000 person-months, respectively. HPV16 and HPV6 had the highest incidence, lowest clearance rate and longest duration of infection among Hr-HPV and low-risk HPV (Lr-HPV) types, respectively. Receptive anal sex is a risk factor for any HPV [hazard ratio (HR) = 1.66, 95% CI: 1.16–2.38] and Hr-HPV infection (HR = 1.99, 95% CI:1.39–2.85). Recent anal sex without condom use was significantly associated with any HPV (HR = 1.80, 95% CI: 1.10–2.94) and Hr-HPV infection (HR = 2.60, 95% CI: 1.42–4.77). Age ≥35 years was significantly associated with Lr-HPV HPV infection only (HR = 1.40, 95% CI: 1.02–1.93). Both inserted and receptive anal sex (HR = 0.60, 95% CI: 0.40–0.89) and anal sex ≥2 times per week (HR = 0.61, 95% CI: 0.43–0.87) were associated with reduced Hr-HPV clearance. Six of the nine-valent vaccine types (HPV6, 11, 16, 18, 52 and 58) occurred most frequently, which indicates the need for high vaccination coverage in MSM.ConclusionsIn this cohort study, high incidence and low clearance of any HPV, Hr-HPV and individual HPV infections emphasize the importance of MSM vaccination. Modifiable behavioral factors such as condoms and drug use should be incorporated into HPV prevention strategies.</p

Insight into the Mechanism for Catalytic Activity of the Oxygen/Hydrogen Evolution Reaction on a Dual-Site Catalyst

The dual-site catalysts consisting of two adjacent single-atom sites on graphene have exhibited promising catalytic activity of the electrochemical oxygen/hydrogen evolution reaction (OER/HER). However, the electrochemical mechanisms of the OER/HER on dual-site catalysts have still been ambiguous. In this work, we employed density functional theory calculations to study the catalytic activity of the OER/HER with a O–O (H–H) direct coupling mechanism on dual-site catalysts. Specifically, these element steps should be classified into two categories: a step evolving proton-coupled electron transfer (PCET step) that needs to be driven by electrode potential and a step without PCET (non-PCET step) that occurs naturally under mild conditions. Our calculated results show that both the maximal free energy change (ΔGMax) contributed by the PCET step and the activity barrier (Ea) of the non-PCET step must be examined to evaluate the catalytic activity of the OER/HER on the dual site. Importantly, it is a basically inevitable negative relationship between ΔGMax and Ea, which would play a critical role in guiding the rational design of effective dual-site catalysts for electrochemical reactions

Energy-Dependent Z‑Scheme via Metal-Interfacing Two-Dimensional p‑Type and n‑Type Semiconductor Layers for Efficient Optoelectronic Conversion

Hybrid heterostructures are a promising type of materials framework for optoelectronic conversion. We designed a ternary energy-dependent thin layer of Cu2S–Pt–WO3 (p-type–metal–n-type) heterojunction to explore an alternative way of realizing efficient charge separation. First-principles calculations showed that the Fermi level of the whole system is lined up via the mediation of Pt metal, which fosters the combination of holes in Cu2S and electrons in WO3 and keeps electrons in Cu2S and holes in WO3 well separated. Importantly, creation of band bending and charge polarization steer low-energy charges selectively to the intermediate metal and keep high-energy charges on individual semiconductors apart. Our simulation analysis of two-dimensional layers with the metal bridge shows increased charge flows across the junction compared to that of their bulk counterparts. Overall, this heterojunction is viable for suppressing recombination of photogenerated electron–hole pairs and augmented electrons per surface that would allow enhanced optoelectronic conversion

Decomposition of CH₂O by Lanthanum: A Theoretical Study

This work aims to investigate the reaction mechanism of lanthanum atom with formaldehyde in the gas phase using density functional theory and coupled cluster calculations. The results indicate that the minimum energy pathway, similar to the reactions of its neighboring yttrium with formaldehyde, is the formation of the η2-formaldehyde−metal complex followed by two C−H insertions which leads to metal dihydrides and carbon monoxide. The competing pathway producing a metal−carbonyl compound and hydrogen molecule favors a high-spin state and thus involves a spin conversion from doublet state to quartet state. The crossing region of the doublet and quartet potential energy surfaces (PES) has been estimated by a simple approach as proposed by Yoshizawa et al. Less favorable pathways leading to metal monoxide and carbene radical by C−O insertion as well as formyllanthanum by single C−H insertion are also studied. Compared with the CCSD(T) method, the BP86 method tends to overestimate the binding energies of the d-rich compounds, though the two methods qualitatively agree well on the reaction mechanism. Finally, the (n − 1)dns to (n − 1)d2ns1 promotion effect is proposed to account for the difference in the formation mechanism of the metal−carbonyl compounds LaCO and YCO, which may also extend to the reactions of formaldehyde with other “general” group III rare earth elements including Sc, Ce, Gd, and Lu

Real-Time, Time-Dependent Density Functional Theory Study on Photoinduced Isomerizations of Azobenzene Under a Light Field

The trans to cis photoisomerization of azobenzene and its reverse (i.e., the cis to trans) processes are studied using real-time propagation time-dependent density functional theory combined with molecular dynamics for ions. We show that the wavelength of the applied laser may significantly affect the transition process. The simulations also show that the photon-excited electrons play essential roles in the isomerization processes, in which the hot electrons couple to phonon modes that drive the transitions