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Early/late heterobimetallic complexes are widely recognized as one of the most effective catalysts for activating coupling reactions. Herein, DFT calculations were used to investigate the specific mechanisms of terminal alkyne dimerization facilitated by two types of Zr/Co complexes: the bis (phosphinoamide) complex B and the mono (phosphinoamide) complex C. In addition, their reaction activities were compared with that of three ligand‐bridged Zr/Co complex A. The results show that the activated mechanisms of the three reactions are similar, all of them contain inner‐ and outer‐sphere mechanisms, and the inner one is the optimal process. Compared to A, the terminal alkyne dimerizations activated by B and C have the lower energy barriers and better selectivity for the E‐isomer; thus, the mono‐ and bis‐(phosphinoamide) Zr/Co complexes are expected to show better activity and selectivity than tris (phosphinoamide) complexes. The stereoselectivity of E‐, Z‐, and gem‐isomers is controlled by the reductive elimination process. The IRI analysis reveals that the selectivity for E‐ and Z‐isomers is influenced due to the notable repulsion and vdW interaction between the second alkyne and the MeNPMe2 ligand. Our work provides a theoretical basis for experimental applications and offers inspiration for the design of high selectivity heterobimetallic complexes. [ABSTRACT FROM AUTHOR]

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. Key points: Informal carers of people with dementia contend with unique circumstances that render them susceptible to both loneliness and social isolation.There is a significant prevalence of loneliness and social isolation in informal carers of individuals with dementia.Several significant moderators influence the prevalence of loneliness and social isolation among informal carers of individuals with dementia.Moderator analysis can guide targeted interventions and support systems for at‐risk informal carers of people with dementia to alleviate loneliness and social isolation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Recently, the green and high efficient of chalcogen bond (ChB) catalysis has been aroused great interest. In this work, the ChB catalysis has been applied to the intramolecular Rauhut‐Currier (RC) reaction of bis(enones). The mechanism was divided into four processes: the promoter addition process, the carbon‐carbon bond coupling process, the hydrogen transfer process, and the promoter elimination process. This study shows that the ChB catalyst could act on the promoter and reactant in the RC reaction, respectively. And the path 2 of ChB catalyst direct acting on the reactant is considered to be a relatively favorable channel of the reaction due to a lower energy barrier. In addition, all six catalysts could achieve good catalytic effect. Analysis of the properties shows that the formation of chalcogen bond mainly promotes the charge transfer of LP(O)−BD*(C−Se) in the carbon‐carbon bond formation (key step), so that the charge of C(4) atom become more positive, thereby accelerating the reaction. [ABSTRACT FROM AUTHOR]

Given the extraordinary versatility in chemical reactions and applications, boron compounds have gained increasing attentions in the past two decades. One of the remarkable advances is the unprecedented preparation of unsaturated boron species. Notably, Braunschweig et al. found that the cyclic (alkyl)(amino) carbenes (CAACs) stabilized diboron molecules (CAAC)2B2(SR)2 host unpaired electrons and exist in the 90°‐twisted diradical form, while other analogues, such as N‐heterocyclic carbenes (NHCs), stabilized diboron molecules prefer a conventional B=B double bond. Since previous studies recognized the differences in the steric effect between CAAC and NHC carbenes, here we focused on the role of thiol substituents in (CAAC)2B2(SR)2 by gradually localizing involved electrons. The co‐planarity of the thiol groups and the consequent captodative effect were found to be the culprit for the 90°‐twisted diradical form of (CAAC)2B2(SR)2. Computational analyses identified two forces contributing to the π electron movements. One is the "push" effect of lone pairs on the sulfur atoms which boosts the π electron delocalization between the BB center and CAACs. The other is the π electron delocalization within each (CAAC)B(SR) fragment where the pull effect originates from the π electron withdrawal by CAACs. There are two such independent and orthogonal push‐pull channels which function mainly in individual (CAAC)B(SR) fragments. This enhanced π push‐pull effect in the triplet state facilitates the electronic excitation in (CAAC)2B2(SR)2 by reducing the singlet‐triplet gap. [ABSTRACT FROM AUTHOR]

The hydrogen‐bonded organic frameworks (HOFs) have rarely been considered for photocatalytic application, given their weak stability and low activity. One presumably effective strategy to improve the photocatalytic performance of the HOFs is to produce a core–shell composite by fabricating a particular nanostructure using stable HOFs. To this end, the surface‐functionalized metal–organic frameworks (MOFs) are used as the host matrix to support the in situ assembly and subsequent multisite growth of the stable HOFs. MOF@HOF eventually obtains core–shell hybrids, i.e., NH2‐UiO‐66@DAT‐HOF. This newly synthesized core–shell nanostructure exhibits excellent stability and superb photocatalytic performance. For example, in terms of tetracycline degradation, the optimal composite presents an apparent reaction rate constant of 60.7 and 7.6 times higher than its parent materials NH2‐UiO‐66 and DAT‐HOF. Such a pronounced enhancement in photocatalytic efficiency of the hybrid material is attributed to the broader visible‐light utilization range compared to its individual parent material as well as the efficient separation of charge carriers supported by the S‐scheme heterojunction. In addition, it is particularly notable that the photocatalytic efficiency of the yielded core–shell nanostructure can remain high after several‐cycle applications. This work provides a universal scheme for synthesizing the MOF@HOF core–shell hybrids. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The carbonyl–olefin ring‐closing metathesis reactions have become a powerful tool for carbon‐carbon bond formation. In this work, the halogen bond catalysis and classical Lewis acid catalysis on the carbonyl–olefin ring‐closing metathesis reaction were investigated by density function theory. For both the halogen bond catalysis and classical Lewis acid catalysis, the carbonyl–olefin ring‐closing metathesis reaction occurs by [2 + 2]‐cycloaddition process and [2 + 2]‐cycloreversion process, the reaction energy barriers are low, therefore, it can be performed easily at room temperature. The essential difference of the two kinds of catalysts is that the catalytic mechanism of halogen bond catalysis is mainly contribution of electrostatic interaction, while that of classical Lewis acid catalysis is mainly catalyzed by orbital interaction. The halogen bond donor catalysts (ICl3, IF3) are expected to be efficient catalysts for the reaction and further promote the chemical synthesis of carbonyl–olefin ring‐closing metathesis reaction. [ABSTRACT FROM AUTHOR]

The Mukaiyama aldol reaction is a powerful tool for the construction of the carbon–carbon bond and the formation of β‐hydroxycarbonyl compounds. In this work, the mechanism of acetaldehyde and 2‐siloxy‐1‐propene both in the absence and presence of the catalyst BF3 was investigated based on density functional theory. The mechanism includes two major steps: the formation of the carbon–carbon bond and the removal of SiH3/BF2 by water. The energy barrier of the carbon–carbon bond formation process in the presence of BF3 is obviously lower, indicating that BF3 is a good catalyst for this reaction. In terms of molecular configuration, the different tensions between the five‐membered‐ring and six‐membered‐ring can be considered as the possible reason for the catalytic effect of BF3. In terms of charge transfer, the charges of natural population analysis in the carbon atom of the carbonyl group in acetaldehyde becomes more positive, which is easier to attack by nucleophiles and promote the nucleophilic process. [ABSTRACT FROM AUTHOR]

Recently, the halogen bonding catalysis in Aza‐Diels‐Alder reaction is increasing gloriously. In this work, the mechanism of the Aza‐Diels‐Alder reaction between imine and Danishefsky's diene catalyzed by N‐heterocyclic imidazole halogen bond donors has been explored with density functional theory. It is revealed that the reaction has two possible pathways: [4+2] cycloaddition pathway and Mannich pathway, in agreement with experimental predictions. Formation of halogen bond between the iodine atom of the catalysts and the N atom of the imine, results in lower energy barriers and more favorable of the reaction. The catalytic effect of the halogen bond can result in the electron rearrangement, which facilitates the formation of C−C bond. The stronger electron‐withdrawing ability of the group bonded to iodine atom of catalysts is, the better the catalytic activity is. These findings could be helpful to develop halogen bond donor catalysts in organic reactions. [ABSTRACT FROM AUTHOR]

The noncovalent interactions involving heteronuclear ethylene analogues H2CEH2 (E = Si, Ge and Sn) have been studied by the Møller–Plesset perturbation theory to investigate the competition and cooperativity between the hydrogen/halogen bond and π‐hole bond. H2CEH2 has a dual role of being a Lewis base and acid with the region of π‐electron accumulation above the carbon atom and the region of π‐electron depletion (π‐hole) above the E atom to participate in the NCX···CE (X = H and Cl) hydrogen/halogen bond and CE···NCY (Y = H, Cl, Li and Na) π‐hole bond, respectively. When HCN/ClCN interacts with H2CEH2 by two sites, the strength of hydrogen bond/halogen bond is stronger than that of π‐hole bond. The π‐hole bond becomes obviously stronger when the metal substituent of YCN (Y = Li and Na) interacting with H2CEH2, showing the character of partial covalent, its strength is much greater than that of hydrogen/halogen bond. In the ternary complexes, both hydrogen/halogen bond and π‐hole bond are simultaneously strengthened compared to those in the binary complexes, especially in the systems containing alkali metal. [ABSTRACT FROM AUTHOR]

In recent years, anion‐anion halogen bonds and neutral‐anion halogen bonds have received extensive attention. In this work, the possibility of halogen bonding of neutral and anionic forms of para‐substituted iodine derivatives of dithiobenzoic acid and its Se‐ and Te‐based congeners with halide anions has been investigated. The anion‐anion complexes are not favorable in the gas phase because of the repulsive effect between anionic halogen bond donors and acceptors. A local minimum is present in the potential energy surface between the −S2CC6H4I and X (X=F−, Cl−, Br−), and the anion‐anion complexes −S2CC6H4I ⋅⋅⋅ X(X=F−, Cl−, Br−) are metastable in the gas phase. Solvation is beneficial to the formation of the anion‐anion complexes. The neutral‐anion complexes are stable in both the gas phase and the polar solvents. The anion‐anion halogen bonds tend to be stable in polar solvents, while the neutral‐anion halogen bonds are stronger in the gas phase than in solvents. [ABSTRACT FROM AUTHOR]

The insertion of an alkyne into transition metal–hydrogen bonds is a key elementary step in catalytic polymerization and hydrogenation processes. It was found that a (Z)‐ or (E)‐type alkyenyl complex can be formed through trans/cis stereospecific processes. In this work, the reaction mechanism of Cp2M(L)H [Cp = η5‐C5H5; M = Nb, V; L = CO, P (OMe)3] with dimethylacetylene dicarboxylate (DMAD), and the factors influencing the stereoselectivity have been investigated based on density functional theory calculations. The calculated results show that all of the reactions are exothermic. For L = CO, the Z‐isomer product forms first even at low temperatures because of the low Gibbs free energy barrier (ΔG#). Then the Z‐pro converts to E‐pro, while for L = P (OMe)3, the exclusive product is the E‐isomer. For different metal centers, the reaction mechanisms of the Cp2M(CO)H + DMAD (M = Nb and V) reaction are similar, while their products are different at room temperature. For M = Nb, because the energy barrier of the isomerization from Z‐pro to E‐pro is low and the relative free energies of Z‐pro and E‐pro are almost equal, both Z‐pro and E‐pro can be obtained. While for the Cp2V(CO)H + DMAD reaction, only the Z‐pro can be obtained under mild conditions, E‐pro can be obtained only at high temperatures. For the Cp2M(CO)H+DMAD(M=V and Nb) reactions, the formation of E‐isomer products proceeds via two five‐membered ring transition states. The calculated results provide an reasonable explanation for the experimental results and predict a new insertion reaction. [ABSTRACT FROM AUTHOR]

The mechanism of ring‐opening polymerization of L‐lactide by iodine trichloride (ICl3) catalyst has been explored by using density functional theory (DFT) calculations and three catalytic pathways were proposed. The first and second pathways belong to the halogen bond catalysis, and the third pathway involves the ICl3 catalysts participating in reactions. When the carbonyl group was maintained involved in the reaction and activated catalytically by the halogen bond, there are two possible pathways. The first pathway involves only one transition state, and the second pathway requires two transition states. There is another pathway in which ICl3 directly participates in the reaction, it is named the third pathway. Two different transition states of the four‐membered rings are generated successively, the transfer of I─O bonds determined the progress of the reaction. Theoretical calculations in this work provide the most basic understanding of ring‐opening polymerization of L‐lactide by ICl3 catalysts. © 2019 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The "windmill" pattern cyclic halogen polymers (XBr)3 (X = Cl, Br, I) and (BrY)n (n = 3–6, Y = Cl, Br, I) have been investigated using the density functional theory. Due to the anisotropic distribution of its electron density, the halogen atom can form halogen‐bonded interactions by functioning as both electron donor sites and electron acceptor sites. For (XBr)3 (X = Cl, Br, I) trimers, the Cl···Cl interaction is the weakest, and the I···I interaction is the strongest. For (BrY)n (n = 3–6, Y = Cl, Br, I), the Br···Br halogen bonds are the strongest in (BrY)4 tetramers. We predict that the iodine‐4 synthon may allow creation of a self‐assembled island during crystal growth. The angle formed by the electron‐depleted sigma‐hole, the halogen atom and the electron‐rich equatorial belt perpendicular to the bond direction, together with the halogen‐bond angle, can be used to explain the geometries and strength of the halogen‐bond interactions. © 2018 Wiley Periodicals, Inc. M06‐2X calculations with def2‐TZVPD basis set was used to investigate the halogen‐n (n = 3–6) synthons to form the "windmill" pattern bonding. [ABSTRACT FROM AUTHOR]

Abstract: The intermolecular π‐hole···π‐electrons interactions between F2ZO (Z = C, Si, Ge) molecules and unsaturated hydrocarbons including acetylene, ethylene, 1,3‐butadiene and benzene were constructed to reveal the differences of tetrel bonds forming by carbon and heavier tetrel atoms. The ab initio computation in association with topological analysis of electron density, natural bond orbital, and energy decomposition analysis demonstrate that the strength of Si···π and Ge···π tetrel bonds is much stronger than that of C···π tetrel bonds. The Si···π and Ge···π tetrel bonds exhibit covalent or partially covalent interaction nature, while the weak C···π tetrel bonds display the hallmarks of noncovalent interaction, the electrostatic interaction is the primary influencing factor. The Si···π and Ge···π interactions are determined by both the σ‐ and π‐electron densities, while the C···π interactions are dominated mainly by the π‐electron densities. The π‐hole···π‐electrons tetrel bonds are dominated by electrostatic interaction, and polarization has a comparable contribution in the Si···π and Ge···π tetrel bonds. [ABSTRACT FROM AUTHOR]

The enhancing effects of molecule X (X = PH2Cl, SHCl, ClCl) on S···S and Se···Se chalcogen-chalcogen bonds in the cyclic trimers SHCl···SHCl···X and SeHCl···SeHCl···X were investigated by calculations at the MP2/aug-cc-pVTZ level. When molecule X is added to the dimer SHCl···SHCl (SeHCl···SeHCl), cyclic trimers are formed. Compared with the dimer, all the cyclic trimers have shorter S···S (Se···Se) lengths, greater electron densities, negative three-body interaction energies, and larger second-order perturbation energies. These results indicate that the addition of molecule X strengthens the original S···S (Se···Se) bond. For the SHCl···SHCl···X cyclic trimers, the S···S bond is strongest in SHCl···SHCl···PH2Cl, weaker in SHCl···SHCl···SHCl, and weakest in SHCl···SHCl···ClCl. This same trend is observed for the Se···Se bond in SeHCl···SeHCl···X. This means that PH2Cl provides the greatest enhancement to the S···S (Se···Se) interaction. [ABSTRACT FROM AUTHOR]

The π-hole of triphosphorus hydride (P3H3) and its derivatives Z3 X3 ( Z = P, As; X = H, F, Cl, Br) was discovered and analyzed. MP2/aug-cc-pVDZ calculations were performed on the π-hole interactions in the HCN... Z3 X3 complexes and the mutual influence between π-hole interactions and the hydrogen bond in the HCN...HCN... Z3 X3 and HCN... Z3 X3...HCN complexes studied. The π-hole interaction belongs to the typical closed-shell noncovalent interaction. The linear relationship was found between the most positive electrostatic potential of the π-hole ( VS,max) and the interaction energy. Moreover, the VS,max of the π-hole was also found to be linearly correlated to the electrostatic energy term, indicating the important contribution of the electrostatic energy term to the π-hole interaction. There is positive cooperativity between the π-hole interaction and the hydrogen bond in the termolecular complexes. The π-hole interaction has a greater influence on the hydrogen bond than vice versa. The mutual enhancing effect between the π-hole interaction and the hydrogen bond in the HCN...HCN... Z3 X3 complexes is greater than that in the HCN... Z3 X3...HCN complexes. [ABSTRACT FROM AUTHOR]

The σ-hole of M2H6 (M = Al, Ga, In) and π-hole of MH3 (M = Al, Ga, In) were discovered and analyzed, the bimolecular complexes M2H6···NH3 and MH3···N2P2F4 (M = Al, Ga, In) were constructed to carry out comparative studies on the group III σ-hole interactions and π-hole interactions. The two types of interactions are all partial-covalent interactions; the π-hole interactions are stronger than σ-hole interactions. The electrostatic energy is the largest contribution for forming the σ-hole and π-hole interaction, the polarization energy is also an important factor to form the M···N interaction. The electrostatic energy contributions to the interaction energy of the σ-hole interactions are somewhat greater than those of the π-hole interactions. However, the polarization contributions for the π-hole interactions are somewhat greater than those for the σ-hole interactions. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The positive electrostatic potentials (ESP) outside the σ-hole along the extension of OP bond in OPH3 and the negative ESP outside the nitrogen atom along the extension of the CN bond in NCX could form the Group V σ-hole interaction OPH3⋯NCX. In this work, the complexes NCY⋯OPH3⋯NCX and OPH3⋯NCX⋯NCY (X, YF, Cl, Br) were designed to investigate the enhancing effects of Y⋯O and X⋯N halogen bonds on the P⋯N Group V σ-hole interaction. With the addition of Y⋯O halogen bond, the VS, max values outside the σ-hole region of OPH3 becomes increasingly positive resulting in a stronger and more polarizable P⋯N interaction. With the addition of X⋯N halogen bond, the VS, min values outside the nitrogen atom of NCX becomes increasingly negative, also resulting in a stronger and more polarizable P⋯N interaction. The Y⋯O halogen bonds affect the σ-hole region (decreased density region) outside the phosphorus atom more than the P⋯N internuclear region (increased density region outside the nitrogen atom), while it is contrary for the X⋯N halogen bonds. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The nature of the interactions of cyanide with lithium and hydrogen halides was investigated using ab initio calculations and topological analysis of electron density. The computed properties of the lithium-bonded complexes RCN···LiX (R = H, F, Cl, Br, CCH, CHCH2, CH3, C2H5; X = Cl, Br) were compared with those of corresponding hydrogen-bonded complexes RCN···HX. The results show that both types of intermolecular interactions are 'closed-shell' noncovalent interactions. The effect of substitution on the interaction energy and electron density at the bond critical points of the lithium and hydrogen bonding interactions is similar. In comparison, the interaction energies of lithium-bonded complexes are more negative than those of hydrogen-bonded counterparts. The electrostatic interaction plays a more important role in the lithium bond than in the hydrogen bond. On complex formation, the net charge and energy of the Li atom decrease and the atomic volume increases, while the net charge and energy of the H atom increase and the atomic volume decreases. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The intermolecular interactions existing at three different sites between phenylacetylene and LiX (X = OH, NH2, F, Cl, Br, CN, NC) have been investigated by means of second-order Møller−Plesset perturbation theory (MP2) calculations and quantum theory of 'atoms in molecules' (QTAIM) studies. At each site, the lithium-bonding interactions with electron-withdrawing groups (F, Cl, Br, CN, NC) were found to be stronger than those with electron-donating groups (OH and NH2). Molecular graphs of C6H5CCH···LiF and πC6H5CCH···LiF show the same connectional positions, and the electron densities at the lithium bond critical points (BCPs) of the πC6H5CCH···LiF complexes are distinctly higher than those of the σC6H5CCH···LiF complexes, indicating that the intermolecular interactions in the C6H5CCH···LiX complexes can be mainly attributed to the π-type interaction. QTAIM studies have shown that these lithium-bond interactions display the characteristics of 'closed-shell' noncovalent interactions, and the molecular formation density difference indicates that electron transfer plays an important role in the formation of the lithium bond. For each site, linear relationships have been found between the topological properties at the BCP (the electron density ρb, its Laplacian ∇2ρb, and the eigenvalue λ3 of the Hessian matrix) and the lithium bond length d(Li-bond). The shorter the lithium bond length d(Li-bond), the larger ρb, and the stronger the π···Li bond. The shorter d(Li-bond), the larger ∇2ρb, and the greater the electrostatic character of the π···Li bond. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Series of typical π-type and pseudo-π-type halogen-bonded complexes B ···ClY and B ···BrY and hydrogen-bonded complex B ···HY (B = C2H4, C2H2, and C3H6; Y = F, Cl, and Br) have been investigated using the MP2/aug-cc-pVDZ method. A striking parallelism was found in the geometries, vibrational frequencies, binding energies, and topological properties between B ···XY and B ···HY (X = Cl and Br). It has been found that the lengths of the weak bond d(X ···π)/ d(H ···π), the frequencies of the weak bond ν(X ···π)/ν(H ···π), the frequency shifts Δν(XY)/Δν(HY), the electron densities at the bond critical point of the weak bonds ρc(X ···π)/ρc(H ···π), and the electron density changes Δρc(XY)/Δρc(HY) could be used as measures of the strengths of typical π-type and pseudo-π-type halogen/hydrogen bonds. The typical π-type and pseudo-π-type halogen bond and hydrogen bond are noncovalent interactions. For the same Y, the halogen bond strengths are in the order B ···ClY < B ···BrY. For the same X, the halogen bond strength decreases according to the sequence F > Cl > Br that is in agreement with the hydrogen bond strengths B ···HF > B ···HCl > B ···HBr. All of these typical π-type and pseudo-π-type hydrogen-bonded and halogen-bonded complexes have the 'conflict-type' structure. Contour maps of the Laplacian of π electron density indicate that the formation of B ···XY halogen-bonded complex and B ···HY hydrogen-bonded complex is very similar. Charge transfer is observed from B to XY/HY and both the dipolar polarization and the volume of the halogen atom or hydrogen atom decrease on B ···XY/B ···HY complex formation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

We present theoretical evidence that the two types of interactions exist in the complexes formed between methylenecyclopropane (MECP) and XY (X, Y = H, F, Cl, and Br). Two seats of XY interacted with MECP are located: (a) is via the pseudo‐π bonding electron pair associated with a CC bond of the cyclopropane ring and (b) is via the typical‐π bonding of electron pair of the CC bond of MECP. These two types of weak interactions are compared based on the calculated geometries, interaction energies, frequency changes, and topological properties of electron density. The integration of electron density over the interatomic surface is found to be a good measure for the strength of weak interaction. Furthermore, the total electron density and separated σ and π electron densities are also computed and discussed in this article. The separated electron density shows σ electron density determined the strength and π electron density influenced the direction of the hydrogen/halogen bond. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

Chalcogen bond (ChB) catalysis, as a new type in the field of non‐covalent bond catalysis, has become a hot research topic in the field of organocatalysis in recent years. In the present work, we investigated the catalytic performance of a series of hypervalent ChB catalysis based on the intramolecular Aza‐Michael reaction of aminochalcone. The reaction includes the carbon‐nitrogen bond coupling step (key step) and the proton transfer step. The catalytic performance of mono‐dentate pentafluorophenyl chalcogen bond donor ChB1 was comparable to that of bis‐dentate chalcogen bond donor ChB4, and stronger than that of mono‐dentate chalcogen bond donors ChB2 and ChB3. The formation of the chalcogen bond between the catalyst and the carbonyl oxygen atom of the reactant, causing the charge rearrangement of the reactant and C(1) charge of the −C−Ph group to become more positive, thereby the ChB catalysis promoted the nucleophile reaction. The electron density of the chalcogen bond of the pre‐complex, the most positive electrostatic potentials of the catalyst, and the NPA charge of the key atom are proportional to the Gibbs energy barrier of the C−N bond coupling process, which provides an idea to predict the catalytic activity of the ChB catalysis. [ABSTRACT FROM AUTHOR]

Given the extraordinary versatility in chemical reactions and applications, boron compounds have gained increasing attentions in the past two decades. One of the remarkable advances is the unprecedented preparation of unsaturated boron species. Notably, Braunschweig et al. found that the cyclic (alkyl)(amino) carbenes (CAACs) stabilized diboron molecules (CAAC)2B2(SR)2 host unpaired electrons and exist in the 90°‐twisted diradical form, while other analogues, such as N‐heterocyclic carbenes (NHCs), stabilized diboron molecules prefer a conventional B=B double bond. Since previous studies recognized the differences in the steric effect between CAAC and NHC carbenes, here we focused on the role of thiol substituents in (CAAC)2B2(SR)2 by gradually localizing involved electrons. The co‐planarity of the thiol groups and the consequent captodative effect were found to be the culprit for the 90°‐twisted diradical form of (CAAC)2B2(SR)2. Computational analyses identified two forces contributing to the π electron movements. One is the "push" effect of lone pairs on the sulfur atoms which boosts the π electron delocalization between the BB center and CAACs. The other is the π electron delocalization within each (CAAC)B(SR) fragment where the pull effect originates from the π electron withdrawal by CAACs. There are two such independent and orthogonal push‐pull channels which function mainly in individual (CAAC)B(SR) fragments. This enhanced π push‐pull effect in the triplet state facilitates the electronic excitation in (CAAC)2B2(SR)2 by reducing the singlet‐triplet gap. [ABSTRACT FROM AUTHOR]

The π-hole of triphosphorus hydride (P 3 H 3 ) and its derivatives Z 3 X 3 (Z = P, As; X = H, F, Cl, Br) was discovered and analyzed. MP2/aug-cc-pVDZ calculations were performed on the π-hole interactions in the HCN...Z 3 X 3 complexes and the mutual influence between π-hole interactions and the hydrogen bond in the HCN...HCN...Z 3 X 3 and HCN...Z 3 X 3 ...HCN complexes studied. The π-hole interaction belongs to the typical closed-shell noncovalent interaction. The linear relationship was found between the most positive electrostatic potential of the π-hole (V S,max ) and the interaction energy. Moreover, the V S,max of the π-hole was also found to be linearly correlated to the electrostatic energy term, indicating the important contribution of the electrostatic energy term to the π-hole interaction. There is positive cooperativity between the π-hole interaction and the hydrogen bond in the termolecular complexes. The π-hole interaction has a greater influence on the hydrogen bond than vice versa. The mutual enhancing effect between the π-hole interaction and the hydrogen bond in the HCN...HCN...Z 3 X 3 complexes is greater than that in the HCN...Z 3 X 3 ...HCN complexes.