Loneliness and social isolation among informal carers of individuals with dementia: A systematic review and meta-analysis.

OBJECTIVES: This systematic review and meta-analysis aimed to determine the prevalence of loneliness and social isolation among informal carers of individuals with dementia and to identify potential influencing factors. METHODS: We conducted a comprehensive search across 10 electronic databases, including PubMed, Cochrane, Embase, Web of Science, PsycINFO, CINAHL, Scopus, Chinese Biomedical, China National Knowledge Internet, and WANFANG. Our search strategy covered the inception of the databases up to September 16, 2023, with an updated search conducted on March 8, 2024. Prevalence estimates of loneliness and social isolation, presented with 95% confidence intervals, were synthesized through meta-analysis. Subgroup analyses and meta-regression were employed to explore potential moderating variables and heterogeneity. RESULTS: The study encompassed 27 research papers involving 11,134 informal carers from 17 different countries. The pooled prevalence of loneliness among informal carers of individuals with dementia was 50.8% (95% CI: 41.8%-59.8%), while the pooled prevalence of social isolation was 37.1% (95% CI: 26.7%-47.6%). Subgroup analyses and meta-regression indicated that various factors significantly influenced the prevalence of loneliness and social isolation. These factors included the caregiving setting, study design, the intensity of loneliness, geographical location (continent), data collection time, and the choice of assessment tools. CONCLUSIONS: This study underscores the substantial prevalence of loneliness and social isolation among informal carers of individuals with dementia. It suggests that policymakers and healthcare providers should prioritize the development of targeted interventions and support systems to alleviate loneliness and social isolation within this vulnerable population.

Pressure and temperature dependent kinetics and the reaction mechanism of Criegee intermediates with vinyl alcohol: a theoretical study.

Criegee intermediates (CIs), the key intermediates in the ozonolysis of olefins in atmosphere, have received much attention due to their high activity. The reaction mechanism of the most simple Criegee intermediate CH2OO with vinyl alcohol (VA) was investigated by using the HL//M06-2X/def2TZVP method. The temperature and pressure dependent rate constant and product branching ratio were calculated using the master equation method. For CH2OO + syn-VA, 1,4-insertion is the main reaction channel while for the CH2OO + anti-VA, cycloaddition and 1,2-insertion into the O-H bond are more favorable than the 1,4-insertion reaction. The 1,4-insertion or cycloaddition intermediates are stabilized collisionally at 300 K and 760 torr, and the dissociation products involving OH are formed at higher temperature and lower pressure. The rate constants of the CH2OO reaction with syn-VA and anti-VA both show negative temperature effects, and they are 2.95 × 10-11 and 2.07 × 10-13 cm3 molecule-1 s-1 at 300 K, respectively, and the former is agreement with the prediction in the literature.

Cationic Hypervalent Chalcogen Bond Catalysis on the Povarov Reaction: Reactivity and Stereoselectivity.

Chalcogen bond catalysis, particularly cationic hypervalent chalcogen bond catalysis, is considered to be an effective strategy for organocatalysis. In this work, the cationic hypervalent chalcogen bond catalysis for the Povarov reaction between N-benzylideneaniline and ethyl vinyl ether was investigated by density functional theory (DFT). The catalytic reaction involves the cycloaddition process and the proton transfer process, and the rate-determining step is the cycloaddition process. Cationic hypervalent tellurium derivatives bearing CF3 and F groups exhibit superior catalytic activity. For the rate-determining step, the Gibbs free energy barrier decreases as the positive electrostatic potential of the chalcogen bond catalysts increases. More importantly, the Gibbs free energy barrier has a strong linear correlation with the electrostatic energy of the chalcogen bond in the catalyst-substrate complex. Furthermore, the catalytic reactions include the endo pathway and exo pathway. The C-H⋅⋅⋅π interaction between the substituent of the ethyl vinyl ether and the aryl ring of the N-benzylideneaniline contributes to the endo-selectivity of the reaction. This research contributes to a deeper understanding of chalcogen bond catalysis, providing insights for designing chalcogen bond catalysts with high performance.

Halogen Bond Catalysis: A Physical Chemistry Perspective.

As important noncovalent interactions, halogen bonds have been widely used in material science, supramolecular chemistry, medicinal chemistry, organocatalysis, and other fields. In the past 15 years, halogen bond catalysis has become a developed field in organocatalysis for the catalysts' advantages of being environmentally friendly, inexpensive, and recyclable. Halogen bonds can induce various organic reactions, and halogen bond catalysis has become a powerful alternative to the fully explored hydrogen bond catalysis. From a physical chemistry view, this perspective provides an overview of the latest progress and key examples of halogen bond catalysis via activation of the lone pair systems of organic functional group, π systems, and metal complexes. The research progresses in halogen bond catalysis by our group were also introduced.

Mechanism and Stereoselectivity Control of Terminal Alkyne Dimerization Activated by a Zr/Co Heterobimetallic Complex: A DFT Study.

Heterobimetallic complexes have recently garnered considerable attention in organic synthesis owing to their high activity and selectivity, which surpass those of monometallic complexes. In this study, the detailed mechanisms of terminal alkyne dimerization activated by the heterobimetallic Zr/Co complex, as well as the different stereoselectivities of Me3SiC≡CH and PhC≡CH dimerization, were investigated and elucidated by using density functional theory calculations. After excluding the three-molecule reaction and outer-sphere mechanisms, the inner-sphere mechanism was determined as the most optimal process. The inner-sphere mechanism involves four processes: THF dissociation and coordination of the first alkyne; ligand migration and C-H activation; N2 dissociation and insertion of the second alkyne; and reductive elimination. The stereoselectivity between the E-/Z- and gem-isomers is determined by the C-C coupling mode of the two alkynes and that of the E- and Z-isomers is determined by the sequence of the C-C coupling and hydrogen migration in the reductive elimination process. Me3SiC≡CH dimerization yields only an E-isomer owing to the large differences in the distortion and interaction energies, whereas PhC≡CH dimerization produces an E-, Z-, and gem-isomers owing to the reduced interaction energy differences.

The levels and related factors of posttraumatic growth among nurses: A systematic review and meta-analysis.

WHAT IS KNOWN ON THE SUBJECT?: Nurses often encounter traumatic events in their clinical practice. Trauma can have both negative effects, such as post-traumatic stress disorder and positive effects, such as growth and positive emotions. Posttraumatic growth is beneficial for nurses, as it contributes to positive mental health outcomes and increases life satisfaction. WHAT THE PAPER ADDS TO EXISTING KNOWLEDGE?: Our study confirms that nurses commonly experience posttraumatic growth after being exposed to traumatic events, and the level of growth is moderate. We have identified individual, work-related, and social and organizational factors that may influence the occurrence of posttraumatic growth among nurses. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: Our findings provide valuable insights for interventions aimed at promoting posttraumatic growth among nurses. It is crucial to consider individual factors, work-related factors, and social and organizational factors when designing these interventions. By addressing these factors, healthcare professionals can support nurses in coping with trauma and facilitate their posttraumatic growth. ABSTRACT: INTRODUCTION: While the negative effects of trauma on nurses have been well-documented, it is equally important to focus on ways to promote posttraumatic growth (PTG) among nurses. AIM: This study aims to explore the levels and related factors of PTG among nurses. METHOD: A comprehensive search was conducted across nine databases up to 26 December 2022. The pooled mean score for PTG was calculated and presented with a 95% confidence interval. Subgroup and meta-regression analyses were performed to identify potential moderators of PTG among nurses. RESULTS: A total of 55 studies, involving 35,621 nurses from 11 countries and regions, were included in this review. The pooled scores of the PTG indicated that nurses experienced a moderate level of PTG (55.69, 95% CI: 50.67-60.72). DISCUSSION: Nurses commonly experience PTG following exposure to traumatic events, with a moderate level of PTG. Our systematic review highlights the potential determinants of PTG among nurses, including individual, work-related, and social and organizational factors. IMPLICATIONS FOR PRACTICE: Targeting these factors in interventions can provide nurses with the necessary resources and support to effectively cope with stress and trauma, and potentially facilitate PTG.

Global prevalence of bullying and associated factors among nursing students during clinical practice: A systematic review and meta-analysis.

OBJECTIVE: This meta-analysis aims to estimate the global prevalence of bullying among nursing students during clinical practice and identify associated factors. DESIGN: Systematic review and meta-analysis. REVIEW METHODS AND DATA SOURCES: We conducted a comprehensive literature search across ten databases (PubMed, Cochrane, Web of Science, Embase, CINAHL, PsycINFO, Scopus, Chinese Biomedical, China National Knowledge Internet, and WANFANG) from their inception to January 3, 2023. Two researchers independently screened potentially eligible studies, extracted data, and assessed study quality. Data were analyzed using random-effects or fixed-effects models. Subgroup analyses and meta-regression explored the influence of participant and study characteristics on bullying prevalence. Publication bias and sensitivity analyses were also performed. RESULTS: We included 28 studies (N = 9511) from 13 countries on five continents. The pooled estimate of bullying prevalence among nursing students during clinical practice was 65.60 % (95 % CI 55. 75 to 74.27), with no evidence of publication bias (t = 1.51, p-value = 0.14). Subgroup and moderator analyses highlighted the impact of country, continent, publication year, and assessment tool on bullying prevalence. CONCLUSION: Nursing students face a high prevalence of bullying during clinical practice. Addressing this issue in nursing education requires prioritizing associated factors, fostering a culture of safety, providing effective training, and promoting individual resilience. These actions can prevent and mitigate bullying, creating a supportive and empowering learning environment for future nurses.

Halogen bond catalysis of the [4+2] cycloaddition reaction of 2-alkenylindoles: catalytic modes and stereoselectivity.

Halogen bond donor catalysts have been widely used in organic reactions because they are environmentally friendly, inexpensive and recyclable. The [4+2] cycloaddition reaction is a key reaction in organic synthesis because of its ease of use, fast speed, and wide range of applications. In this work, halogen bond catalysis in the [4+2] cycloaddition reaction between 2-alkenylindoles was investigated based on DFT calculations. There are two modes of I⋯π halogen bond catalysis: either on the ethenyl of 2-alkenylindole (mode A) or on the five-membered ring of 2-alkenylindole (mode B). Both modes involve two steps: the formation of carbon-carbon bonds and the formation of six-membered rings. Gibbs free energy barriers were determined to investigate the stereoselectivity of the endo pathway and exo pathway. For mode A, the exo products were more easily generated when the substituent R = H, and the N-H⋯π interaction promoted high endo selectivity in the case of the substituent R = Ph. For mode B, an increasing proportion of endo products can be obtained in the order of catalyst I2, IBr and ICl. The π⋯π interaction of the substituent R = Ph promotes the [4+2] cycloaddition reaction, which is consistent with the experimental observation that R = Ph has a higher yield than R = H. The study of different catalytic modes and stereoselectivity would provide new ideas for the further study of the [4+2] cycloaddition reaction.

A Real-Time and Robust Neural Network Model for Low-Measurement-Rate Compressed-Sensing Image Reconstruction.

Compressed sensing (CS) is a popular data compression theory for many computer vision tasks, but the high reconstruction complexity for images prevents it from being used in many real-world applications. Existing end-to-end learning methods achieved real time sensing but lack theory guarantee for robust reconstruction results. This paper proposes a neural network called RootsNet, which integrates the CS mechanism into the network to prevent error propagation. So, RootsNet knows what will happen if some modules in the network go wrong. It also implements real-time and successfully reconstructed extremely low measurement rates that are impossible for traditional optimization-theory-based methods. For qualitative validation, RootsNet is implemented in two real-world measurement applications, i.e., a near-field microwave imaging system and a pipeline inspection system, where RootsNet easily saves 60% more measurement time and 95% more data compared with the state-of-the-art optimization-theory-based reconstruction methods. Without losing generality, comprehensive experiments are performed on general datasets, including evaluating the key components in RootsNet, the reconstruction uncertainty, quality, and efficiency. RootsNet has the best uncertainty performance and efficiency, and achieves the best reconstruction quality under super low-measurement rates.

Experiences and perspectives of nurses infected with COVID-19: A qualitative systematic review and meta-synthesis.

This qualitative systematic review aims to comprehensively understand the experiences and perspectives of nurses infected with COVID-19, addressing a significant gap in the current literature. Following the JBI meta-synthesis approach, a rigorous search was conducted across nine electronic databases and references until January 16, 2023. Seventeen eligible studies underwent quality assessment using the JBI critical checklist. Data were synthesized using standardized tools, and the ConQual tool evaluated confidence in the findings. Seven key findings emerged, providing valuable insights into emotional experiences, adaptation to COVID-19 challenges, influence of support systems, coping strategies, posttraumatic growth perceptions, and effects on professional identity and career advancement. The findings highlight emotional toll, adaptive strategies, and professional implications for nurses. Moreover, they emphasize the importance of support systems, coping mechanisms, and posttraumatic growth in promoting nurses' well-being and resilience. These insights have practical implications for targeted interventions and support mechanisms to enhance infected nurses' well-being and improve healthcare outcomes.

USF1 modulates transcription and cellular functions by regulating multiple transcription factors in Huh7 cells.

Liver cancer, including hepatocellular carcinoma (HCC), is a malignant tumor that has high rates of metastasis and mortality worldwide. Upstream transcription factor 1 (USF1) is a canonical transcription factor (TF) and is associated with the pathogenesis of several cancers, but its biological functions and molecular targets in HCC remain unclear. Huh7 cells that overexpress USF1 were used with whole transcriptome profiling through RNA sequencing and chromatin immunoprecipitation (ChIP) sequencing methods to investigate the downstream targets of USF1. Reverse transcription-quantitative PCR was then used to validate the downstream targets. The results showed that USF1 significantly regulates 350 differentially expressed genes (DEGs). The upregulated DEGs were primarily protein-coding genes enriched in immune and inflammation response pathways, while the downregulated DEGs were mainly coding long non-coding (lnc)RNAs, indicating the regulatory function of USF1. It was also demonstrated that USF1 directly binds to the promoter region of 2,492 genes, which may be involved in the viral progression and cell proliferation pathways. By integrating these two datasets, 16 overlapped genes were detected, including downregulated lncRNA-NEAT1 and upregulated TF-ETV5. The downregulated lncRNA-NEAT1 showed reverse expression pattern and prognosis result compared with that of USF1 in patients with liver cancer, while upregulated TF-ETV5 showed consistent results with USF1. Promoter region motif analysis indicated that ETV5 has more binding motifs and genes than USF1 itself for USF1-regulated DEGs, indicating that USF1 may indirectly modulate gene expression by regulating ETV5 expression in Huh7 cells. The study also validated the direct interaction between USF1 and the promoter of ETV5 using ChIP-qPCR. In summary, the results demonstrated that USF1 binds to the promoter region of thousands of genes and affects a large part of DEGs indirectly. Downstream genes, including lncRNA-NEAT1 and TF-ETV5, may also have potential functions in the regulated network by USF1 and have potential functions in the progression of HCC. The present findings suggested that USF1 and its downstream targets could be potential targets for HCC therapy in the future.

Gold(III) derivatives as the noncovalent interaction donors: theoretical study of the π-hole regium bonds.

Except for the well-known σ-hole regium bonds formed by metal nanoparticles and M(I) (M = Cu, Ag, and Au) derivatives, the existence of π-hole regions located above and below the Au atom in gold(III) derivatives suggests that gold(III) also functions as an efficient electrophilic site. In this study, a comprehensive analysis was conducted on the electrophilicity of trichloro-(p-toluonitrilo-N)-gold(III) derivatives AuL3(NCC6H4X) (L = Cl, Br, CN; X = NH2, CH3, CF3, NC, and CN) and the nature of π-hole regium bonds in the AuL3(NCC6H4X)⋯LB (LB = NH3, N(NH3)3, CH2O, C2H2, C2H4, C6H6) and (AuCl3(NCC6H4Y))n (Y = Cl, CN, NC, NO2; n = 2, 3)) complexes. The characteristics of the π-hole regium bonds were studied with respect to the influence of ligands and substituents, the strength of intermolecular interactions between Au(III) derivatives and Lewis bases, and those in the polymers. In the case of the AuL3(NCC6H4X)⋯NH3 complexes, the strength of the regium bonds increases gradually in the order of L = Cl < Br < CN and X = NH2 < CH3 < CF3 ≈ NC < CN. The ligands (L) attached to the Au atom exert a significant effect on the strength of the π-hole regium bonds in comparison to the substituents (X) on the benzene ring. The regium bonds are primarily dominated by electrostatic interaction, accompanied by moderate contribution from polarization. Linear relationships were identified between the electrostatic energies and the local most positive potentials over the Au atom, as well as between the polarization energies and the amount of charge transfer. Most of the π-hole regium bonds in the AuL3(NCC6H4X)⋯LB complexes exhibit the characters of closed shell noncovalent interactions. In the polymers (AuCl3(NCC6H4Y))n, weak face-to-face π-π stacking interactions are also present, in addition to regium bonds. The trimers displayed a slightly negative cooperativity in comparison to the dimers.

Chalcogen Bond Catalysis with Telluronium Cations for Bromination Reaction: Importance of Electrostatic and Polarization Effects.

Recently, chalcogen bond catalysts with telluronium cations have garnered considerable attention in organic reactions. In this work, chalcogen bond catalysis on the bromination reaction of anisole with N-bromosuccinimide (NBS) with the telluronium cationic catalysts has been explored with density functional theory (DFT). The catalytic reaction is divided into two stages: the bromine transfer step and the proton transfer step. Based on the computational results, one can find the rate-determining step is the bromine transfer step. Moreover, the present study elucidates that a stronger chalcogen bond between catalysts and NBS will give better catalytic performance. Additionally, this work also clarified the importance of the electrostatic and polarization effects in the chalcogen bond between the oxygen atom of NBS and the Te atom of the catalyst in this bromination reaction. The electrostatic and polarization effects are significantly influenced by the electron-withdrawing ability of the substitution groups on the catalysts. Moreover, the structure-property relationship between the strength of chalcogen bond, electrostatic effect, polarization effect and catalytic performance are established for the design of more efficient chalcogen bond catalysts.

Iodine(I)-based and iodine(III)-based halogen bond catalysis on the Friedel-Crafts reaction: a theoretical study.

Halogen bond catalysis, especially iodine derivatives catalysis, has attracted increasing attention in recent years owing to the advantages of relatively cheap, stable, green, easy to handle, and favorable catalytic activity. To obtain insights into the catalytic mechanism and activity of halogen bond donor catalysts, iodine(I)-based and iodine(III)-based halogen bond catalysis on the Friedel-Crafts reaction were investigated in this study. The entire reaction contains several key steps: carbon-carbon bond coupling, proton transfer, hydroxyl departure, indole addition, and deprotonation process. According to the energetic span model, iodine(III)-based donor catalysts exhibit higher catalytic activity than iodine(I)-based catalysts and double cationic catalysts are more potent than single cationic ones. For halogen bond catalysis, the Gibbs energy barriers have linear relation to the electron density at the halogen bond critical points. Furthermore, the Gibbs energy barriers are also linearly related to the integral charge values of the increased region of electron density outside the oxygen atom of reactants. Therefore, the stronger halogen bond results in lower Gibbs energy barrier, and the stronger polarization further benefits the halogen bond catalysis.

Stretched Central Double Bonds in Dialumene and Disilene by Amino Substituents: A Case of Lone Pair Repulsion.

There have been remarkable advances in the syntheses and applications of groups 13 and 14 homonuclear ethene analogues. However, successes are largely limited to aryl- and/or silyl-substituted species. Analogues bearing two or more heteroatoms are still scarce. In this work, the block-localized wavefunction (BLW) method at the density functional theory (DFT) level was employed to study dialumene and disilene bearing two amino substituents whose optimal geometries exhibit significantly stretched central M=M (M=Al or Si) double bonds compared with aryl- and/or silyl-substituted species. Computational analyses showed that the repulsion between the lone electron pairs of amino substituents and M=M π bond plays a critical role in the elongation of the M=M bonds. Evidently, replacing the substituent groups -NH2 with -BH2 can enhance the planarity and shorten the central double bonds due to the absence of lone pair electrons in BH2 .

Mechanistic Insights into Oxazolone Synthesis by Bimetallic Au-Pd-Catalyzed Catalysis and Catalyst Design: DFT Investigations.

Bimetallic synergistic catalysis is one of the most effective and powerful strategies for the synthesis of oxazolones, an important species in organic synthesis. In this work, the mechanism of AuCl(PMe3)/AgOTf-Pd(0) ([Au-Pd]) bimetallic catalyst-catalyzed oxazolone synthesis using N-alkynyl carbamates as precursors was studied in detail by DFT calculations and the catalytic performances of a series of bimetallic catalysts were evaluated. The results show that the reaction begins from the [Au]-catalyzed cycloisomerization of N-alkynyl carbamates. After the five-membered intermediate is formed, the [Pd(0)]-catalyzed cycle starts, which contains three steps: oxidation addition, transmetalation, and reductive elimination. The whole reaction belongs to a catalyzed catalysis, and the reductive elimination is the rate-determining step. In the transmetalation process, both the [Pd(0)] catalyst and the ionic bridge are necessary. For the [Au-Pd]-catalyzed process, it is Cl- as the bridge, not OTf-. The cheaper metal compound, AgCl(PMe3), can serve as the alternative of AuCl(PMe3) to co-catalyze with the [Pd(0)] catalyst for the title reaction.

Is there a bidirectional relationship between workplace bullying and the risk of sickness absence? Systematic review and meta-analysis of prospective studies.

Exposure to workplace bullying increases the risk of sickness absence. However, the extent and direction of this relationship for different follow-up lengths are not well established. To provide evidence regarding the direction and extent of the relationship between workplace bullying and different durations of sickness absence. We searched nine databases from their inception to 29 November 2022. Multiple independent observers screened the literature, extracted the data and used the Risk Of Bias In Non-randomised Studies of Exposure to assess the methodological quality. The overall effect sizes of odds ratio, relative risk, hazard ratio and 95% confidence intervals were calculated. Our meta-analysis demonstrated a 26% increased risk of sick leave among workers exposed to workplace bullying for all follow-up lengths (95% CI 1.18 to 1.35), even after adjusting for confounding factors. Moreover, we found a significant association between long-term sickness absence and a higher likelihood of subsequent exposure to workplace bullying, with a pooled OR of 1.63 (95% CI 1.21 to 2.04). Our study established a bidirectional relationship between workplace bullying and long-term sickness absence, highlighting that it increases the risk of sickness absence at different follow-up lengths among employees who have been bullied. Hence, organisations should be mindful of workers who resume work after prolonged absences due to illness and adopt appropriate management strategies to prevent workplace bullying.

Gustatory stimulus interventions for older adults with dysphagia: a scoping review.

BACKGROUND: Gustatory stimulus interventions have been shown to improve swallowing function in older adults with dysphagia. However, the optimal intervention strategies as well as their effects and safety remain unclear. AIMS: To explore current evidence regarding gustatory stimulus interventions for dysphagia in older adults. METHODS: Nine electronic databases (PubMed, Web of Science, Embase, CINAHL, Cochrane Library, China National Knowledge Infrastructure, Wanfang Database, China Science and Technology Journal Database, and Sinomed) were searched from their inception to August 2022. RESULTS: This review identified 263 articles, and 15 met the inclusion criteria. The types of gustatory stimulus interventions included spicy (n = 10), sour (n = 3), and mixed (sour-sweet) stimuli (n = 2), with most studies focusing on spicy stimuli. The most frequently reported spicy stimulus was capsaicin. Further, the most commonly reported intervention frequency was thrice a day before meals for 1-4 weeks. The stimuli concentrations and dosages could not be standardized due to the among-study heterogeneity. These studies reported 16 assessment tools and 42 outcomes, which mainly included videofluoroscopy and swallowing response time respectively. More than half of the included studies reported no adverse effects of gustatory stimulus interventions. CONCLUSION AND DISCUSSIONS: Gustatory stimulus interventions improved swallowing function in older adults with dysphagia. However, assessment tools and outcomes for dysphagia should be standardized in the future, and explore personalized interventions based on different diseases and their stages, to determine the most cost-effective interventions, and to prevent its complications.

Activation of metal-involved halogen bonds and classical halogen bonds in gold(I) catalysis.

In gold(I) catalysis, the activation of Au(I) chloride catalysts via chloride abstraction and noncovalent interactions has become a research focus in organometallic catalysis. In this work, taking halogen bond donors (C4H2INO2, C6F5I, C8H9O2I) as activators for a Au(I) chloride catalyst (Ph3PAuCl), the mechanism of the cyclization reaction of propargylic amide was investigated. It was found that there are two activation modes as design principles to obtain the catalytically active species Ph3PAu+: the halogen bond donors activate the Cl atoms of Ph3PAuCl to form X-I⋯Cl (X = C, N) classical halogen bonds and activate the Au atoms of Ph3PAuCl to form X-I⋯Au (X = C, N) metal-involved halogen bonds. For the two activation modes, the mechanism of the cyclization reaction of propargylic amide has pathways: the chloride abstraction process of the first step and the 5-exo/6-endo cyclization process of the second step. Both activation modes show good activity for the cyclization reaction with the activation ability of classical halogen bonds being slightly stronger than that of the metal-involved halogen bonds, which is consistent with the strength of the X-I⋯Cl halogen bonds being slightly stronger than that of the X-I⋯Au halogen bonds. Therefore, both metal-involved halogen bonds and classical halogen bonds have important development prospects for the activation of catalysts in gold(I) catalysis.

Intrinsic defects at the interface of the FAPbI3/MAPbI3 superlattice: insight from first-principles calculations.

The use of a superlattice structure is an effective strategy to develop novel perovskites and obtain excellent light-absorbing materials. Based on first-principles calculations, we systematically studied the properties of intrinsic point defects at the interface of the FAPbI3/MAPbI3 superlattice. Our calculations show that charged defects are easier to form as compared to neutral ones at the superlattice interface due to low formation energies. Most defects with low formation energies have a shallow level in the band gap, and some deep level defects have high formation energies, so the superlattice perovskite exhibits high defect tolerance. PbI3+ is a dominant and detrimental defect, which acts as a non-radiative recombination center because it has low formation energy and a deep transition level. To avoid the generation of PbI3+ defects, it is suggested to synthesize FAPbI3/MAPbI3 superlattices under I-rich conditions. The calculated light absorption coefficients and photovoltaic performance parameters demonstrate that the presence of defects leads to a certain degree of reduction in light absorption and power conversion efficiency (PCE) of solar cells made of FAPbI3/MAPbI3 superlattices, but the excellent performance of the perovskite solar cell (PSC) is basically retained. The superlattice perovskites are still promising candidates for light-absorbing materials of PSCs. This study is expected to contribute to a better understanding of the properties of defects at the superlattice interface and provide theoretical support for the design of high performance PSCs.