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Mechanisms of the Diels‐Alder (D‐A) reactions between N‐alkyl and aryl‐1,2‐dihydropyridines and dienophiles have been investigated by M06‐2X‐D3/6‐31 + G(d,p) basis set, and SMD model was employed to simulate the solvent effect. The computational results show that the productive process of endo‐product is favorable with lower energy barrier. The calculations of substituent effect indicate that there are some relations between the energy barrier and the productivity. The lower energy barrier means the higher productivity, and the barrier of retro D‐A reaction could also have influence on the productivity. Finally, natural bond orbital Fukui function (NOFF) and frontier molecular orbital theory (FMOT) are employed to analyze the structures and reveal the substances of D‐A reactions. [ABSTRACT FROM AUTHOR]

While the presence of sulfur⋅⋅⋅π bonding interaction is a general phenomenon in the biological systems, the exploitation of this noncovalent force in a chemical process yet remains elusive. Herein, we describe the concept of chalcogen⋅⋅⋅π bonding catalysis that activates molecules of π systems through the interaction between chalcogen and π‐electron cloud. The proof‐of‐concept studies using a vinylindole‐based Diels–Alder benchmark reaction demonstrate that S⋅⋅⋅π and Se⋅⋅⋅π bonding interaction can drive the cycloaddition reaction efficiently. Experimental results suggest that a simultaneously double Se⋅⋅⋅π bonding interaction directs the stereoselectivity in this cycloaddition process. [ABSTRACT FROM AUTHOR]

While the presence of sulfur⋅⋅⋅π bonding interaction is a general phenomenon in the biological systems, the exploitation of this noncovalent force in a chemical process yet remains elusive. Herein, we describe the concept of chalcogen⋅⋅⋅π bonding catalysis that activates molecules of π systems through the interaction between chalcogen and π‐electron cloud. The proof‐of‐concept studies using a vinylindole‐based Diels–Alder benchmark reaction demonstrate that S⋅⋅⋅π and Se⋅⋅⋅π bonding interaction can drive the cycloaddition reaction efficiently. Experimental results suggest that a simultaneously double Se⋅⋅⋅π bonding interaction directs the stereoselectivity in this cycloaddition process. [ABSTRACT FROM AUTHOR]

Diabetic kidney disease (DKD), a major microvascular complication of diabetes, is characterized by its complex pathogenesis, high risk of chronic renal failure, and lack of effective diagnosis and treatment methods. GSK3β (glycogen synthase kinase 3β), a highly conserved threonine/serine kinase, was found to activate glycogen synthase. As a key molecule of the glucose metabolism pathway, GSK3β participates in a variety of cellular activities and plays a pivotal role in multiple diseases. However, these effects are not only mediated by affecting glucose metabolism. This review elaborates on the role of GSK3β in DKD and its damage mechanism in different intrinsic renal cells. GSK3β is also a biomarker indicating the progression of DKD. Finally, the protective effects of GSK3β inhibitors on DKD are also discussed. [ABSTRACT FROM AUTHOR]

A whole dataset containing 55 hydrogen bonds were studied at the MP2/aug-cc-pVTZ level of theory. The changes of geometries and stretching vibrational frequencies show that there are 31 redshifted and 24 blueshifted hydrogen-bonded complexes. Natural bond orbital analysis was carried out at the B3LYP/aug-cc-pVTZ level of theory to obtain the electron densities in the bonding and antibonding orbitals of the proton donor X-H bond, which are closely associated with its bond length. Based on their relationship, a generally applicable method considering both the electron densities in the bonding and antibonding orbitals of the proton donor X-H bond has been developed to quantitatively describe the hyperconjugative effect on the X-H bond length changes in these hydrogen-bonded complexes. [ABSTRACT FROM AUTHOR]

Theoretical investigations of the interactions between carbon monoxide (CO) and bromopentafluorobenzene (C6F5Br) have been carried out at both M06-2X/6-311++G(2d,2p) and M06-2X/aug-cc-pVTZ levels of theory. Because both C and O atom-ends of CO show negative electrostatic potential, they can favorably interact with the positive electrostatic potential generated by the σ-hole of Br and the π-hole of the aromatic ring of C6F5Br, yielding four different dimers and trimers. Their structures, spectroscopy and nature were systematically studied. The competition between the interactions involving the σ-hole of the Br atom and the π-hole of C6F5Br with the C and O atom-ends of CO was illustrated for the dimers and trimers, and meanwhile, the cooperativity between the two components of the trimers was elaborated. In addition, the experimental FT-IR and fluorescence spectra were measured for C6F5Br and the mixed C6F5Br and CO system without and with the solvent of hexane to gain information on the formation of molecular complexes between C6F5Br and CO. The results presented in this work are beneficial for the understanding of the competition and cooperativity of σ- and π-hole intermolecular interactions. [ABSTRACT FROM AUTHOR]

The mechanisms of three cascade reactions between N -methylindole and sulfonylazides via Huisgen cycloaddition were investigated using density functional theory, and the polarized continuum model (PCM) was applied to simulate the solvent effects. Fukui functions and dual descriptor have been employed to assess the atomic reactivity. With respect to these three reactions, each has two possible reaction pathways (I and II). The calculated results show that singlet O 2 plays a crucial role in the oxidative dehydrogenation process in the first reaction between 2-imine indole and p-tosylazide (TsN 3 ), when the reaction occurs without O 2 but with N 2 , two pathways via the processes of breaking two covalent bonds, followed by 1,2-H shift and N 2 removal (or by N 2 removal and 1,2-H shift) exist. Water molecule plays an important role in the H-shift process in the third reaction of the methyl substituted N -methylindole with TsN 3 . Our results demonstrated that these reactions can take place at certain condition, in good agreement with the experimental observation. The understanding of the competitive pathways for Huisgen cycloaddition of N -methylindole and sulfonylazides can provide valuable insights into related reactions. [ABSTRACT FROM AUTHOR]

Intermolecular interactions between phenol and benzene molecules with the T-shaped geometries could be diverse. They can be pursued via two structural series: one with benzene standing above phenol using one or two C–H bonds as the anchoring point and the other with phenol standing on top of benzene with either C–H or O–H bond as the leg. In this work, structure and interaction properties of these species are investigated at the DFT M06-2X/6-311++G(2d,2p) level of theory without and with the counterpoise correction. A total of twelve distinct isomers have been identified, eight of which were unveiled for the first time. It is found that π–π interactions play essential roles in stabilizing these conformations, while C–H/π, C–H···O van der Waals interactions, and C–H···O and O–H/π hydrogen bonds are also involved and positively contribute to the stability of these species. Our energy decomposition analysis shows that the driving force for the formation of these complexes arises from attractive electrostatic, exchange, polarization, and dispersion terms, balanced by the repulsion term. The dispersion effect plays a dominant role, but the electrostatic and exchange terms are also markedly significant. Their close relationships between one another have also been disclosed. [ABSTRACT FROM AUTHOR]

A simple model for describing the non-quasi-equivalent icosahedral virus capsid composed of 72 pentameric capsomeres is developed. By means of six-step operations, a new 4-gons polyhedron P is obtained which contains 72 pentagons, 80 trigons and 210 quadrilaterals. More importantly, it bears icosahedral symmetry. The rationality of the existence of the 4-gons polyhedron P is further discussed. The results show that this model can be used to represent the capsids of papovaviruses. [ABSTRACT FROM AUTHOR]

Context: The reaction between Na and HF is a typical harpooning reaction which is of great interest due to its significance in understanding the elementary chemical reaction kinetics. This work aims to investigate the detailed reaction mechanisms of sodium with hydrogen fluoride and the adsorption of HF on the resultant NaF as well as the (NaF)4 tetramer. The results suggest that the reaction between Na and HF leads to the formation of sodium fluoride salt NaF and hydrogen gas. Na interacts with HF to form a complex HF···Na, and then the approaching of F atom of HF to Na results in a transition state H···F···Na. Accompanied by the broken of H-F bond, the bond forms between F and Na atoms as NaF, then the product NaF is yielded due to the removal of H atom. The resultant NaF can further form (NaF)4 tetramer. The interaction of NaF with HF leads to the complex NaF···HF; the form I as well as II of (NaF)4 can interact with HF to produce two complexes (i.e., (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF), but the form III of (NaF)4 can interact with HF to produce only one complex (NaF)4(III)···HF. These complexes were explored in terms of noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. NCI analyses confirm the existences of attractive interactions in the complexes HF···Na, NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF. QTAIM analyses suggest that the F···Na interaction forms in the HF···Na complex while the F···H hydrogen bonds form in NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF complexes. Natural bond orbital (NBO) analyses were also applied to analyze the intermolecular donor-acceptor orbital interactions in these complexes. These results would provide valuable insight into the chemical reaction of Na and HF and the adsorption interaction between sodium fluoride salt and HF. Methods: The calculations were carried out at the M06-L/6-311++G(2d,2p) level of theory which were performed using the Gaussian16 program. Intrinsic reaction coordinate (IRC) calculations were carried out at the same level of theory to confirm that the obtained transition state was true. The molecular surface electrostatic potential (MSEP) was employed to understand how the complex forms. Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) analysis was used to know the topology parameters at bond critical points (BCPs) and intermolecular interactions in the complex and intermediate. The topology parameters and the BCP plots were obtained by the Multiwfn software. [ABSTRACT FROM AUTHOR]

Design and engineering of highly efficient emitting materials with assembly-induced luminescence, such as room-temperature phosphorescence (RTP) and aggregation-induced emission (AIE), have stimulated extensive efforts. Here, we propose a new strategy to obtain size-controlled Eu3+-complex nanoparticles (Eu-NPs) with self-assembly-induced luminescence (SAIL) characteristics without encapsulation or hybridization. Compared with previous RTP or AIE materials, the SAIL phenomena of increased luminescence intensity and lifetime in aqueous solution for the proposed Eu-NPs are due to the combined effect of self-assembly in confining the molecular motion and shielding the water quenching. As proof of concept, we also show that this system can be further applied in bioimaging, temperature measurement and HClO sensing. The SAIL activity of the rare-earth (RE) system proposed here offers a further step forward on the roadmap for the development of RE light conversion systems and their integration in bioimaging and therapy applications. [ABSTRACT FROM AUTHOR]

Herein, we describe a new catalysis platform, supramolecular carbon‐bonding catalysis, which exploits the highly directional weak interactions between carbon centers of catalysts and electron donors to drive chemical reactions. To demonstrate this catalysis approach, we discovered a class of cyclopropane derivatives incorporated with carbonyl, ester and cyano groups as catalysts which showed general catalysis capability in different types of benchmark reactions. Among these typical examples, a challenging tail‐to‐head terpene cyclization can be achieved by supramolecular carbon‐bonding catalysis. The co‐crystal structures of catalyst and electron donors, comparison experiments, and titrations support a catalysis mode of carbon‐bonding activation of Lewis basic reactants. [ABSTRACT FROM AUTHOR]

Herein, we describe a new catalysis platform, supramolecular carbon‐bonding catalysis, which exploits the highly directional weak interactions between carbon centers of catalysts and electron donors to drive chemical reactions. To demonstrate this catalysis approach, we discovered a class of cyclopropane derivatives incorporated with carbonyl, ester and cyano groups as catalysts which showed general catalysis capability in different types of benchmark reactions. Among these typical examples, a challenging tail‐to‐head terpene cyclization can be achieved by supramolecular carbon‐bonding catalysis. The co‐crystal structures of catalyst and electron donors, comparison experiments, and titrations support a catalysis mode of carbon‐bonding activation of Lewis basic reactants. [ABSTRACT FROM AUTHOR]

The tin-oxo cage ([R12Sn12O14(OH)6]2+) is an excellent photoresist candidate in extreme ultraviolet lithography (EUVL). Photoionization that leads to plenty of photoelectrons and secondary electrons is an inevitable process upon irradiation by EUV light. The secondary electrons could cause electron blur and decrease the resolution of the photoresist. The utilization and improvement are limited owing to its poorly understood fundamental chemical process, such as exposure to EUV. In this study, the property of complexes (bare cage, binary complexes, and ternary complexes) formed by the combination of the cage and different counterions (methanesulfonate, tosylate, and triflate) was explored using density functional theory (DFT). Extended transition state-nature orbital of chemical valence (ETS-NOCV), charge decomposition analysis (CDA), and atomic dipole moment corrected Hirshfeld (ADCH) atomic charge analyses were carried out to characterize the interaction process (including ionization, electron attachment, and cleavage of the carbon–tin bond) and inherent mechanism. The number and species of counterions are closely associated with ionization and electron attachment; however, they show an inconspicuous effect on the carbon–tin bond energy. Meanwhile, tin free radical could be the reactivity site of ionization (and electron affinity). The activity of radical species is affected by counterions; this could be attributed to the changes in the charge density by diverse counterions, which could be an important factor in why the counterion affects the pattern. In addition, a superb linearity between the ADCH of tin free radical and IP/AP was found, which indicate that the atomic charge could be a simple and reliable substitution of complicated calculation for IP (or AP) to screen suitable counterions and improve the resolution of photoresist. [ABSTRACT FROM AUTHOR]

Substituent size and isomerization play an important role in the polymorphism of 2-(naphthalen-n-ylamino)-benzoic acids (n = 1, 2; 2-NBAs) as each of the two previously investigated 2-NBAs was found to be polymorphic, while their parent compound fenamic acid (FA) has only one form discovered. 2-(Naphthalen-1-ylamino)-nicotinic acid (1) and 2-(naphthalen-2-ylamino)-nicotinic acid (2) (2-NNA) are isosteric compounds of 2-NBAs, and 2-(2,3-dimethyl-phenylamino)-nicotinic acid (3) and 2-(3,4-dimethyl-phenylamino)-nicotinic acid (4) are 2-NNA analogues with similar substitution patterns. All four compounds are clonixin analogues. The polymorphism of these four compounds was investigated. One solvent-free form (1-A) and one hydrate (1-H) were discovered for 1, three forms (2-I, 2-II, and 2-III) were obtained for 2, and one form was found for 3 and 4. The four systems were characterized by single-crystal XRD (SCXRD) and powder XRD (PXRD), and structural properties were compared among the crystals of the four compounds, their isosteres, and other related analogues. The phase behavior of the four systems was studied with differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) was used to investigate the dehydration of 1-H. Computational studies such as stable conformer search, π–π interaction energy calculation, and non-covalent interaction (NCI) analysis were performed to shed light on the rise of polymorphism, and the relative contribution of various intermolecular interactions to the overall stability of the crystals. The study confirmed the effect of substituent size, thus the consequent π–π interactions, on the hydrate formation of compound 1 and polymorphism of compound 2. [ABSTRACT FROM AUTHOR]

Copigmentation was investigated in model solutions between the anthocyanin malvidin-3- O -glucoside and three phenolic aldehydes (vanillic, syringic and coniferyl aldehydes) as a function of the pH and the pigment/copigment molar ratio. Tristimulus colorimetry was applied to evaluate the chromatic variations induced by copigmentation process. The results indicated that the greatest magnitude of copigmentation was obtained at pH 3.0 and molar ratio of 1:100, being significantly higher with coniferyl aldehyde, followed by syringic and vanillic aldehydes. The equilibrium constant ( K ) and Gibbs free energies (Δ G °) determined here show a spontaneous exothermic reaction. Theoretical calculations (Δ G binding , Δ E ) specified the relative arrangement of the pigment and copigment molecules within the complexes. In addition, an atoms in molecules (AIM) analysis was used to explore the main driving forces contributing to the formation of copigmentation complexes. [ABSTRACT FROM AUTHOR]

The copigmentation effect between malvidin-3- O -glucoside and three hydroxycinnamic acids ( p -coumaric, caffeic and ferulic acids) on the color expression was assessed in red wine model solutions. The colorimetric parameters indicated that the increasing concentration of these copigments could enhance the color intensity of the wine-like solutions (hyperchromic effect and bathochromic shift), and displayed the darker and more vivid bluish chromatic properties. The equilibrium constant ( K ), stoichiometric ratio ( n ) and thermodynamic parameters (∆ G °, ∆ H °, ∆ S °) were determined by the spectrophotometric methods, showing the generally spontaneous exothermic character of the process. In addition, quantum chemical investigations were performed to interpret the absorption differences. The results showed that the ferulic acid was the more powerful copigment compared with the other two hydroxycinnamic counterparts, indicating that the copigmentation was not only correlated to the concentration of the copigments but also strongly dependent on their molecular structures. AIM analysis was also used to explore the driving forces contributing to the copigmentation, which suggested that the hydrogen bond and van der Waals interactions were the main driving forces for the three pigment–copigment complexes. [ABSTRACT FROM AUTHOR]

Experimental studies on the Kolbe–Schmitt reaction and its side reactions have made great progresses; however, the relative theoretical studies fall behind. In order to study the mechanism of the Kolbe–Schmitt reaction with 2,6-di-tert-butylphenol and 2,4-di-tert-butylphenol as reactants, we carried out theoretical calculation studies at the M06-2X/Def2-SVP/SMD level of theory using the Gaussian 09 D.01 software package. For the reactant 2,6-di-tert-butylphenol, there is a dynamic equilibrium between the main product and side product, which can rapidly transform into each other at 160 °C by crossing the Gibbs free energy barrier of 14.1 kcal/mol. Moreover, the relative Gibbs free energy of the main product and side product is close; both of them may be observed in the experimental system. However, for 2,4-di-tert-butylphenol, the main product is thermodynamically favorable due to its lower Gibbs free energy, while the side product is kinetically favorable due to the lower activation energy barrier; the main product and the side product compete with each other. We hope the study can shed light on the Kolbe–Schmitt reaction. [ABSTRACT FROM AUTHOR]

• The reaction mechanism of the asymmetric passerini reaction catalyzed by chiral phosphoric acid (CP6) was theoretically investigated. • The effect of weak interactions on the enantioselectivity of the reaction was revealed. • The activation mechanism of CP6 in the reaction was elucidated. The enantioselective control of the three-component Passerini reaction was successfully achieved using chiral phosphoric acid as a catalyst with a wide range of substrates and high stereoselectivity. Quantum mechanical calculations reveals the detailed reaction mechanism and enantioselective origin of the reaction. The calculations revealed that the chiral phosphoric acid first forms a stable heterodimer with the carboxylic acid substrate, followed by C- C and C- O bond formations, the generation of a five-membered cyclic intermediate, and finally acyl migration to yield the product. Four reaction paths for the overall process were identified and compared to determine the optimal major and by-product paths. The enantioselective origin of the reaction has been elucidated systematically using distortion/interaction theory and truncated model system. QTAIM and IGMH analyses demonstrated the type and strength of interaction between catalyst and the substrates. The calculated e.e. value was 93 %, which was in good agreement with the experimental value. It is expected that the results of this study will offer new insights into the field of asymmetric Passerini reactions. [Display omitted] [ABSTRACT FROM AUTHOR]

The selective oxidation of aniline to metastable and valuable azoxybenzene, azobenzene or nitrosobenzene has important practical significance in organic synthesis. However, uncontrollable selectivity and laborious synthesis of the expensive required catalysts severely hinders the uptake of these reactions in industrial settings. Herein, we have pioneered the discovery of Zr(OH)4 as an efficient heterogeneous catalyst capable of the selective oxidation of aniline, using either peroxide or O2 as oxidant, to selectively obtain various azoxybenzenes, symmetric/unsymmetric azobenzenes, as well as nitrosobenzenes, by simply regulating the reaction solvent, without the need for additives. Mechanistic experiments and DFT calculations demonstrate that the activation of H2O2 and O2 is primarily achieved by the bridging hydroxyl and terminal hydroxyl groups of Zr(OH)4, respectively. The present work provides an economical and environmentally friendly strategy for the selective oxidation of aniline in industrial applications. [ABSTRACT FROM AUTHOR]

The selective oxidation of aniline to metastable and valuable azoxybenzene, azobenzene or nitrosobenzene has important practical significance in organic synthesis. However, uncontrollable selectivity and laborious synthesis of the expensive required catalysts severely hinders the uptake of these reactions in industrial settings. Herein, we have pioneered the discovery of Zr(OH)4 as an efficient heterogeneous catalyst capable of the selective oxidation of aniline, using either peroxide or O2 as oxidant, to selectively obtain various azoxybenzenes, symmetric/unsymmetric azobenzenes, as well as nitrosobenzenes, by simply regulating the reaction solvent, without the need for additives. Mechanistic experiments and DFT calculations demonstrate that the activation of H2O2 and O2 is primarily achieved by the bridging hydroxyl and terminal hydroxyl groups of Zr(OH)4, respectively. The present work provides an economical and environmentally friendly strategy for the selective oxidation of aniline in industrial applications. [ABSTRACT FROM AUTHOR]

First principles investigation and Hirshfeld surface analysis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) crystals have been carried out. The geometrical and electronic structures of TATB molecules in the crystal and gas phases were compared. The Hirshfeld surface analysis of the TATB crystal structure shows that the intermolecular H⋯O interactions make important contributions in stabilizing the TATB crystal, while other intermolecular H⋯N and H⋯C interactions, O⋯O, N⋯O, C⋯O, and C⋯N close contacts also make contributions. QTAIM analyses of the intermolecular interactions in the molecular pairs confirm the presence of these intermolecular interactions based on Hirshfeld surface analyses, indicating that these intermolecular interactions play important roles in the crystal. The reason why the TATB crystal adopts a high energy conformer in which the NO2 and NH2 groups are coplanar with the benzene ring is elaborated. The cooperativity between hydrogen bonding and π⋯π interactions in the TATB crystal is verified and illustrated. [ABSTRACT FROM AUTHOR]

Cu2O-based composites for photocatalysis have been extensively explored owing to their promising application in solving environmental and energy problems. At present, the research on photocatalysis is focused on improving the photocatalytic performance of materials. It has been reported that adjusting the morphology and size of Cu2O can effectively improve its photocatalytic property. However, photocorrosion is still an inevitable problem, which hinders the application of Cu2O in photocatalysis. The strategies of constructing heterogeneous nanostructures and ion doping can significantly improve the light stability, light absorption capacity and separation efficiency of electron–hole pairs. Cu2O-based composites exhibit superior performances in degrading organic matter, producing hydrogen, reducing CO2 and sterilization. Therefore, the construction of multi-materials will be one of the future directions in their photocatalytic application. This review summarizes the recent strategies for enhancing the photocatalytic activity of Cu2O by analyzing different Cu2O-based photocatalysts, and the charge transfer pathway is further discussed in detail. Finally, several opportunities and challenges in the field of photocatalysis are illustrated. [ABSTRACT FROM AUTHOR]

Monoalkylation of aniline can be readily achieved using trichloroacetimidate as an alkylating agent and a Brønsted acid, such as (±)-camphorsulfonic acid, as a catalyst. In this study, systematic theoretical calculations were performed to understand the reaction mechanism for the monoalkylation of 2,5-dichloroaniline with trichloroacetimidate catalyzed by (±)-camphorsulfonic acid; moreover, the judgement about whether the reaction takes place via an SN1 or SN2 mechanism was elaborated. The two possible proton-transfer reaction mechanisms proposed herein based on the experimental results were investigated; moreover, another two possible reaction mechanisms involving the activation of both 2,5-dichloroaniline and trichloroacetimidate by (±)-camphorsulfonic acid via dual hydrogen-bonding activation modes were evaluated. The calculated results suggest that the reaction between 2,5-dichloroaniline and trichloroacetimidate catalyzed by (±)-camphorsulfonic acid preferentially occurs through the SN1 mechanism based on the dual hydrogen-bonding activation modes. [ABSTRACT FROM AUTHOR]

Triethylene diamine (DABCO) has the characteristic of being hydrophilic and exhibits a color change in air because its N atom can interact with H2O and CO2. To understand these phenomena, herein, theoretical calculations on the intermolecular interactions between DABCO and H2O (or CO2) were carried out at the M06-2X/aug-cc-pVDZ level without and with the counterpoise method, and single-point calculations at the CCSD(T)/aug-cc-pVDZ level were also performed. The electron donating ability of DABCO was revealed by the molecular surface electrostatic potential and Fukui function. The driving forces for the formation of a dimer and trimer were uncovered by EDA analyses. Because DABCO can interact with both H2O and CO2, the formation of hydrogen bonds and tetrel bonds is competitive, and meanwhile, DABCO can interact with H2O and CO2 simultaneously, so the hydrogen bond and tetrel bond can coexist and cooperate with each other. The hydrogen bond and tetrel bond in the dimers and trimers were proven and analyzed by NCI and QTAIM. The results presented here will provide useful insight in understanding the hydrophilic characteristic and the color change of DABCO. [ABSTRACT FROM AUTHOR]

Physisorption of bromopentafluorobenzene (C6F5Br) on graphene can occur due to the unique σ-hole and π-hole characters of C6F5Br and the rich π-electrons region of graphene, leading to the formation of three types of π-hole···π and σ-hole···π interactions. The π-hole···π interactions are even stronger than the σ-hole···π interactions. The property of graphene was significantly affected by such physisorption. [ABSTRACT FROM AUTHOR]

• The copigmentation of danshensu, caffeic acid and rosmarinic acid was studied. • Spectroscopic, thermodynamic and theoretical methods were followed. • Color parameters of oenin were enhanced in the presence of the three copigments. • The fluorescence spectra indicated the interaction between caffeic acid and oenin. • Hydrogen bonds in copigmentation were confirmed by FTIR spectroscopic results. The copigmentation effects of polyphenol with different structures vary greatly. Therefore, the aim of this study is to investigate possible interactions in red wine model solutions between oenin and three phenolic compounds: danshensu, caffeic acid and rosmarinic acid. Our results show that the copigmentation of rosmarinic acid is the strongest among the compounds tested. The colourimetric parameters indicate that colour intensity becomes enhanced with increasing concentration of these copigments, leading to darker and more vivid bluish colours. Thermodynamic and quantum chemical investigations are performed to interpret the absorption properties in the visible range. Fluorescence spectroscopy confirms the interaction between caffeic acid and oenin, while FTIR spectroscopic results further suggest a role for hydrogen bonds in the overall process. To our knowledge, this is the first experimentally corroborated direct evidence of hydrogen bonds in copigmentation. [ABSTRACT FROM AUTHOR]

Bromo- and iodo-pentafluorobenzene (C6F5X, X = Br, I) exhibit intriguing σ- and π-hole characters, which are able to accept electrons, whereas furan (C4H4O) and thiophene (C4H4S) are able to donate electrons because of their electron-rich atoms and groups (i.e., the O atom and π-ring in C4H4O and the π-ring in C4H4S). Theoretical investigations of intermolecular interactions in these systems (i.e., C4H4O and C6F5Br, C4H4S and C6F5Br, C4H4O and C6F5I, and C4H4S and C6F5I) have been carried out at the M06-2X/aug-cc-pVDZ and wB97-XD/aug-cc-pVDZ levels with and without the counterpoise method, together with single-point calculations at the CCSD(T)/aug-cc-pVDZ level. For the system of C4H4O and C6F5X (X = Br, I), five different dimers, namely, I–V and I′–V′, which are connected by σ-hole…n, σ-hole…π and π-hole…π bonds, were found. Moreover, for the system of C4H4S and C6F5Br, four different dimers, namely, VI–IX, which are connected by σ-hole…π and π-hole…π bonds, were found. However, five dimers, namely, VI′–X′, were found for the system of C4H4S and C6F5I, which are connected by σ-hole…π, π-hole…π and σ-hole…n bonds. The driving forces for the formation of these dimers were revealed by EDA analyses. NCI, QTAIM and NBO analyses were employed to prove the existence of intermolecular interactions in these dimers and to elucidate their nature. The results presented here will be insightful for the study of other intermolecular systems that involve σ- and π-holes. [ABSTRACT FROM AUTHOR]

The crystallization of 3‐chloroisonicotinic acid (3‐CINA) can lead to three crystal forms (I, II and III), but 3‐CINA in each form has different conformation. The three crystal forms have different lattice energies. The intermolecular interactions in the molecular pairs involving the conformer in each crystal were evaluated, it is found that the sum of these intermolecular interaction energies in each crystal has a linear relationship with the corresponding lattice energy. QTAIM analyses for the intermolecular interactions of molecular pairs correspond to Hirshfeld surface analyses for the crystal form, illustrating that the stability of the crystal is closely associated with the intermolecular interactions involving the conformer in the asymmetric unit of the crystal. 3‐chloroisonicotinic acid (3‐CINA) has three crystal forms (I, II and III), first principles investigation and Hirshfeld surface analysis have been employed to explore them. [ABSTRACT FROM AUTHOR]

To uncover the correlation between the bond length change and the corresponding stretching frequency shift of the proton donor D-H upon hydrogen bond formation, a series of hydrogen-bonded complexes involving HF and HCl which exhibit the characteristics of red-shifted hydrogen bond were investigated at the MP2/aug-cc-pVTZ, M062X/aug-cc-pVTZ, and B3LYP/aug-cc-pVTZ(GD3) levels of theory with CP optimizations. A statistical analysis of these complexes leads to the quantitative illustrations of the relations between bond length and stretching vibrational frequency, between bond length and bond force constant, between stretching vibrational frequency and bond force constant, between bond length and bond order for hydrohalides in a mathematical way, which would provide valuable insights into the explanation of the geometrical and spectroscopic behaviors during hydrogen bond formation. [ABSTRACT FROM AUTHOR]

Carbon monoxide can interact with two dihalogen molecules XY (X, Y = Cl, Br) in the form of X(Y)⋯C OX(Y)⋯C O⋯X(Y)X(Y) trimeric complex, and their nature and characteristics were investigated at MP2/aug-cc-pVDZ level without and with counterpoise method, together with single point calculations at CCSD(T)/aug-cc-pVDZ level. The optimized geometries, stretching modes and interaction energies of a series of X(Y)⋯C OX(Y)⋯C O⋯X(Y)X(Y) trimeric complexes were obtained and discussed. The cooperativity in these complexes was evaluated. EDA analyses reveal that the electrostatic interaction is the dominant net driving force in each trimer, but the contributions of other interactions like exchange, dispersion and polarization interactions are also important. QTAIM and NCI analyses confirm the existence of attractive halogen-bonding interactions. Additionally, EDDMF analysis was employed for the component dimers of these trimers, which indicates that the formation of halogen-bonding interactions is closely related to the charge shift and the rearrangement of electronic density in the formation of these complexes. The results would provide valuable insight into for these linear halogen bonds. [ABSTRACT FROM AUTHOR]

Prototype lanthanide metal–organic frameworks (LnMOFs), Ln(BTC) (Ln = Eu and Tb; BTC = benzene-1,3,5-tricarboxylate), have been considered as luminescent sensors for detecting toxic anions, while their neutral pore structures have limited the entrance and encapsulation of anions to produce highly anion-responsive photoluminescence (PL). To facilitate anions to enter the pore space of Ln(BTC), a one-pot synthesis method was proposed in which BTC was partially replaced with its structural analogue L·BF4 (H3L·BF4 = 2,4,6-tricarboxy-1-methylpyridinium tetrafluoroborate) which consists of an anion affinity site of cationic methylpyridinium. Compared to the original Ln(BTC), the co-doped cationic framework Eu0.05Tb0.95-BTC0.9L0.1 is highly sensitive for detecting different toxic anions by tuning the energy absorption of organic chromophores, the energy transfer efficiency to Ln3+ ions and the energy allocation between different Ln3+ ions in the PL spectra. We demonstrated that the Eu0.05Tb0.95-BTC0.9L0.1 PL sensor has the capability of decoding various toxic anions with a clearly differentiable and unique emission intensity ratio of 5D4→7F5 (Tb3+, 545 nm) to 5D0→7F2 (Eu3+, 618 nm) transitions (ITb/IEu). Compared to Ln(BTC), the co-doped Eu0.05Tb0.95-BTC0.9L0.1 presents self-calibrating, high distinguishable and stable PL signals for detecting toxic anions. [ABSTRACT FROM AUTHOR]

Two molecules with different conformations appear in the asymmetric unit of fenamic acid crystal (Z′ = 2). The two conformations have higher energies, and they dimerize via asymmetric O–H…O hydrogen bonds. For the predicted crystal (Z′ = 1), the symmetric O–H…O hydrogen bonds form between the lower energy conformers. Quantum mechanical calculations were carried out to elaborate the existence of higher energy conformers and their special arrangements. The asymmetric O–H…O hydrogen bonds in the crystal (Z′ = 2) are even stronger than the symmetric O–H…O hydrogen bonds in the predicted crystal (Z′ = 1), which is an important reason that the crystal with Z′ = 2 is observed. Additionally, intricate intermolecular interactions, that is, many adjacent molecules interacting with the substituted and unsubstituted benzene groups of higher energy conformers, also come into play, and these interactions cooperate and stabilize the conformers. A comparison of these intermolecular interactions in the crystal (Z′ = 2) with those in the predicted crystal (Z′ = 1) was made. The potential factors holding the two higher energy conformers together as a packing motif have been discussed in detail. We expect that the results could shed light on the understanding of the origin of the Z′ = 2 structure and other higher Z′ structures. [ABSTRACT FROM AUTHOR]

• The mechanisms for organocatalytic synthesis of chiral allene by racemic propargylic alcohol and 3-phenylindole were proposed. • Eight possible reaction pathways were found after the dehydration process. • The intermolecular interactions including HBs and π-π interactions play crucial roles in determining the enantioselectivity. Organocatalytic synthesis of chiral allene can be successfully achieved through the reaction between propargylic alcohol and 3-phenylindole catalyzed by chiral phosphoric acid with high yield and high enantioselectivity. The detailed reaction mechanism and origin of enantioselectivity were uncovered by quantum mechanical calculations. The results indicate that the reactions undergo the dehydration process, the C–C bonding reaction, the hydrogen abstraction and the regeneration of catalyst. Eight possible pathways were found and the most favorable reaction paths leading to the major and minor products were evaluated which were consistent with the experimental results. The distortion/interaction analyses of the transition states in enantioselectivity-determining steps confirm the most favorable pathway in leading the major product. QTAIM and IGM analyses are used to illustrate the role of intermolecular interactions. EDA analysis is also employed to understand the origin of selectivity. This work would provide insightful viewpoints on the asymmetric organocatalytic reaction by chiral phosphoric acid. [Display omitted] [ABSTRACT FROM AUTHOR]

• Phenolic acids inhibit the volatilization of ethyl acetate. • The hydroxyl and methoxy groups of phenolic acids affected the inhibition effect. • Hydrophobic effect might drive the spontaneous binding of the two compounds. • There was an electron transfer between phenolic acids and ethyl acetate. Hydroxycinnamic acids and ethyl acetate were assessed in simulated alcohol-free wine solutions to explore the effect of phenolic acids on the aroma volatility of esters. The results showed that the phenolic acids could inhibit the volatilization of ethyl acetate, and the extent of inhibition was influenced by the concentration and structure of the phenolic compounds. The ultraviolet absorption spectra of the phenolic acids and ethyl acetate confirmed the interaction between the two compounds. The thermodynamic parameters of the interaction implied a spontaneous exothermic interaction, driven primarily by hydrophobic effects. Meanwhile, the results of the fluorescence-quenching analysis indicated electron transfer between the reactants. The quantum chemical investigations revealed negative and positive charge density distributions in the structures of ethyl acetate and the phenolic acids, respectively. These results will provide some data reference and theoretical support for further research on the effects of phenolic acid matrix on other structural esters. [ABSTRACT FROM AUTHOR]

In the present research, the copigmentations of malvidin-3- O -glucoside with five hydroxybenzoic cofactors ( p -hydroxybenzoic acid, protocatechuic acid, gallic acid, vanillic acid, and syringic acid) were investigated. The influence of the concentration of these cofactors and the reaction temperature was examined. The equilibrium constant ( K ), stoichiometric ratio ( n ) and the thermodynamic parameters (Δ G °, Δ H °, Δ S °) related to the copigmentation were also reported here. Theoretical calculations were performed to identify the relative arrangement between the pigment and cofactors in the copigmentation complexes. Besides, the comparison of the relative binding free energies (ΔΔ G binding ) derived from the theoretical calculations and experimental data were made, and the binding strength of these copigmentation complexes was discussed with the interaction energies (Δ E ). AIM analysis was also used to explore the main driving forces contributing to the copigmentation. In the comparison of the five studied cofactors, syringic acid had a stronger copigmentation effect than the other four phenolic acids investigated. [ABSTRACT FROM AUTHOR]

The high-energetic and low-sensitive explosive material of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) was theoretically investigated by first principles calculations and Hirshfeld surface analysis. The experimental and partly optimized LLM-105 crystals were compared which indicated that it is important to correct the hydrogen positions. Hirshfeld surface analyses of the experimental and partly optimized LLM-105 crystals were also compared, which showed that the intermolecular H⋯O interactions significantly contribute to the stability of the LLM-105 crystal, while the contributions of other intermolecular interactions in the experimental and partly optimized LLM-105 crystals are quite different. The geometrical and electronic structures of LLM-105 molecules in the experimental and partly optimized crystals as well as that in the gas phase were compared. QTAIM analysis was employed to illustrate the existences of intermolecular interactions in the molecular pairs taken from partly optimized LLM-105 crystal, and the types of intermolecular interactions from QTAIM analysis are in agreement with the results of Hirshfeld surface analysis. The reason why the LLM-105 molecule in the partly optimized crystal adopts a non-coplanar structure in which the NO 2 and NH 2 groups is not coplanar with the six-membered ring is elaborated. The existence of cooperativity among different intermolecular interactions were verified by analysing the trimeric complexes formed among three LLM-105 molecules in the partly optimized crystal. The non-coplanar of the NO 2 and NH 2 groups with the six-membered ring in LLM-105 molecule is favorable in forming more intermolecular interactions which cooperate and stabilize the crystal. [Display omitted] • The explosive material of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) crystal was investigated theoretically. • The single LLM-105 molecule, the dimeric and trimeric complexes were analyzed. • The non-coplanar LLM-105 molecule favors the formation of more intermolecular interactions which stabilize the crystal. • The cooperativity among the intermolecular interactions was verified. [ABSTRACT FROM AUTHOR]

The equilibrium geometries, growth patterns, stabilities, and electronic properties of bimetallic BeSi ( n = 1-11) clusters are systematically investigated at the B3LYP/6-311G(d) level of theory. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. The optimized results suggest that the three-dimensional structures are observed for the most stable isomers of BeSi clusters when n > 2. The calculated vertical ionization potential for the lowest-energy isomers are comparable to the experimental values of Si. According to the averaged binding energy, fragmentation energy, second-order energy difference and HOMO-LUMO gaps calculations, we identify that the BeSi and BeSi clusters are more stable, and Be atoms doping enhance the chemical reactivity of the Si host. The natural population and natural electron configuration analyses indicate that the Be atoms possess positive charge at n = 1-5 but negative charge at n = 6-11. The chemical hardness of BeSi clusters show three local maxima at n = 2, 5, and 9, whereas three local minima are found for the corresponding chemical potential, meaning these clusters are more stable than their neighboring cluster sizes. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Ternary NiO/Ag/RGO nanocomposites were synthesized as an electrochemical sensor for nanomolarity detection of Sunset Yellow in soft drink. [Display omitted] • Ternary NiO/Ag/RGO exhibited high electrocatalytic activity for SY oxidation. • NiO/Ag/RGO held a low LOD of 13 nM and good selectivity for SY detection. • The electrochemical sensor was successfully employed for SY detection in soft drinks. NiO nanoparticles (NPs) with small Ag NPs loading supported on reduced graphene oxide nanosheets (ternary NiO/Ag/RGO nanocomposites) were synthesized via a hydrothermal process followed by high-temperature calcination, extending the synergistic effects among noble metal, metal oxide and carbon materials. Based on ternary NiO/Ag/RGO nanocomposites, a new electrochemical sensor was fabricated for the detection of sunset yellow (SY) in soft drinks through cyclic voltammetry, Tafel plot and differential pulse voltammetry. The experimental conditions were optimized and kinetic parameters studied. Due to the synergistic effect of the ternary components, the prepared sensor exhibited superior electroanalytical performance toward SY detection, including wide linear range from 0.1 to 50 μM and from 50 to 450 μM, low detection limit of 13 nM, excellent specificity against various interfering colorants, good reproducibility and stability. Importantly, the electrochemical sensors was successfully employed for quantitative SY analysis in soft drinks with satisfactory recoveries, where the analyzed results were also in agreement with LC/MS analysis. [ABSTRACT FROM AUTHOR]

The rich π-electrons region of graphene enables it to be a good material which can interact with many organic molecules. As a low-sensitivity and high-energy explosive, 1,1-diamino-2,2-dinitroethene and its dimer possess unique characters including hydrogen bonds and π bond which can adsorb on graphene through physisorption. The results suggest that the adsorption energies have a very small difference on the different adsorption sites. Due to the physisorption, the geometrical and electronic properties of 1,1-diamino-2,2-dinitroethene and its dimer vary significantly. The intramolecular as well as intermolecular hydrogen bond strengths are considerably affected due to the π···π interaction of 1,1-diamino-2,2-dinitroethene or its dimer with graphene. The cooperativity between intermolecular hydrogen bonds and π···π interactions is observed which causes wax of intermolecular hydrogen bonds and wane of π···π interactions. The physisorption of 1,1-diamino-2,2-dinitroethene or its dimer also leads to the variation of electronic property of graphene. The physisorptions of 1,1-diamino-2,2-dinitroethene and its dimer on graphene have been investigated theoretically. Image 1 • The physisorptions of 1,1-diamino-2,2-dinitroethene and its dimer on graphene have been investigated theoretically. • The geometrical and electronic properties of 1,1-diamino-2,2-dinitroethene and its dimer vary significantly. • The cooperativity between intermolecular hydrogen bonds and π···π interactions is observed. • The physisorption of 1,1-diamino-2,2-dinitroethene or its dimer modulates the electronic property of graphene. [ABSTRACT FROM AUTHOR]

Abstract: In the work, we report a facile template-free approach to prepare hollow VO2 microspheres. Uniform hollow VO2 assemblies composed of ordered microspheres with an average diameter of 3.0µm and a hollow interior of 2.0µm were prepared by calcining the precursor, which was synthesized via heat preservation process sealed in Teflon-lined stainless autoclave in the presence of urea. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scan electron microscopy (SEM) have been used to characterize VO2 microspheres. The proposed mechanism for the formation of hollow VO2 microspheres is discussed. [Copyright &y& Elsevier]