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Quantum anomalous Hall (QAH) insulators (or Chern insulators) have attracted much attention due to their exotic properties. However the ultra-low critical temperature restricts their potential applications. Based on first-principles calculations, we propose that chalcogenide monolayers PdTaX2 (X = Se, Te) are ferromagnetic Chern insulators with a Chern number of. Their Curie temperatures both exceed 1000 K. Furthermore, the spin–orbit coupling (SOC) induced global band gaps of PdTaSe2 and PdTaTe2 are as large as 350 meV and 566 meV, respectively. The combined merits of high Curie temperature and large nontrivial band gap of PdTaX2 (X = Se, Te) show the potential to break through the critical temperature restriction of QAH. Considering the spin-polarized edge states of PdTaX2 (X = Se, Te), they are also potential candidates for spintronics. [ABSTRACT FROM AUTHOR]

Construction of the pyridine ring is a practical and streamline way to construct a variety of quindoline derivatives. We have developed a novel method for synthesis of quindoline derivatives by means of intramolecular ring-closure reactions of 3-N-methylphenylindoles via an iminium salt intermediate. This practical method has the advantages of a short reaction time, operational simplicity, and nearly quantitative yields; and it can be used for the rapid synthesis of a variety of valuable quindoline derivatives. [ABSTRACT FROM AUTHOR]

Recently, there has been growing interest in the field of flat-band physics due to its attractive properties and wide range of practical applications. In this study, we introduce two novel two-dimensional monolayers, namely B3C11O6 and B3C15O6, which exhibit a flat band near the Fermi level. These monolayers have been found to be energetically favorable, dynamically stable, and thermodynamically stable based on formation energies, phonon spectra, and molecular dynamics simulations. The nearly flat band (NFB) in B3C11O6 arises from the extended kagome sublattice of carbon atoms. Due to the strong interaction between carbon atoms beyond their nearest neighbors, the bandwidth of the initial flat band is extended to approximately 0.5 eV. Nevertheless, there is still a prominent peak in the density of states near the Fermi level. On the other hand, the NFB in B3C15O6 originates from the localized states of the carbon five-ring structure, which forms a distorted kagome lattice. The presence and characteristics of the NFB strongly depend on the interactions between next-nearest neighbors. Interestingly, the partially occupied NFB in B3C11O6 leads to spin splitting, resulting in a transformation of the system into a ferromagnetic metal. Our research not only presents two types of lattices capable of hosting flat bands or NFBs, but also provides two monolayers that can be employed to investigate various intriguing quantum phases. [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]

The chemistry of cyclic sulfinic acid derivatives (sultines and cyclic sulfinamides) was underdeveloped for a long time due to their inaccessibility. Considering the importance of cyclic sulfinate esters and amides in the fields of chemistry, pharmaceutical science, and material science, synthesis strategies involving cyclic sulfinic acid derivatives have been paid more attention in recent years, and have been widely used in the synthesis of sulfur-containing compounds such as sulfoxides, sulfones, sulfinates and thioethers. Despite the impressive improvements that have been made in last twenty years with the new strategies, to date, no reviews have been published, to the best of our knowledge, dealing with the preparation of cyclic sulfinic acid derivatives. This review summarizes the latest advances in the development of new synthesis methods to access cyclic sulfinic acid derivatives in the last two decades. The synthetic strategies are reviewed by highlighting their product diversity, selectivity and applicability, and the mechanistic rationale is presented where possible. We wish to bring readers a comprehensive understanding of the state-of-play of cyclic sulfinic acid derivative formation and make a contribution to future research. [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]

Direct difunctionalization of olefins—which are the most commonly used compounds in organic synthesis—is a powerful tool for rapid formation of structurally complex building blocks from readily available starting materials. However, difunctionalization of unactivated olefins remains a formidable challenge. Herein, we describe a green, cost-effective, and eco-friendly electrochemical protocol for selective chlorosulfuration or chlorosulfoxidation of unactivated alkenes. This electrochemical method creates the potential possibility for the preparation of high-value-added products in a more sustainable and greener manner. [ABSTRACT FROM AUTHOR]

Two new copper(I) iodide-based hybrids, i.e. (Py3P–O–PPy3)(Cu2I4) (1) and (Py3P–O–PPy3)(Cu4I6) (2) (Py = pyrrolidine), have been prepared, in which the tripodal diphosphonium (Py3P–O–PPy3)2+ is in situ generated in the one-pot synthesis. The disordered (Cu4I6)2− tetramers are rare with two sets of tetracuprate centers. Interestingly, 1 exhibits sensitive luminescence mechanochromism, which is ascribed to the disturbed cuprophilic Cu⋯Cu interactions and the crystalline packing adjustment by destroying C–H⋯I hydrogen bonds during mechanical force. In particular, the luminescence thermochromism is unique, whose fluorescence intensity is strengthened with the elevated temperature. This could be due to the S2–S1 internal conversion on the linear P–O–P backbone, which will be bent upon heating. Simultaneous luminescence thermo/mechanochromism can also be monitored in 1. However, no luminescence thermo/mechanochromic performances can be detected in 2, so the luminescence thermo/mechanochromism of 1 could be quenched with DMF. The conclusions in this work might provide a new large-scale synthesis strategy for intelligent responsive luminescent materials. [ABSTRACT FROM AUTHOR]

Strong electron-poor cation diphenyliodonium was firstly incorporated with transition metal thiocyanates to obtain three new photo-sensitive hybrids, (DPI)3[Mn(SCN)5(H2O)]·0.25H2O (α-1), {(DPI)2[Ni(SCN)4]}n (α-2) and {(DPI)6[Cd3(SCN)12]}n (α-3) (DPI+ = diphenyliodonium), whose photo-induced structural transformations to corresponding β-phases have been disclosed. After irradiating, all the MX6 octahedrons stretch clearly along the M–S directions, and C–H⋯π interactions and the secondary hypervalent I(III)⋯S halogen bonds are weakened. The hydrogen bonds are also weakened, except for those in 1. Time-dependent solid-state UV-vis spectra, PXRD patterns and EPR spectra before and after irradiating were obtained to prove the irreversible structural transformations of the hybrids, during which minor structural adjustments occurred. Consequently, the fluorescence emission changed from blue (α-3) to yellow (β-3) upon irradiation. Interestingly, obvious photomagnetization on 1 with a χMT increase of 14.89% and photodemagnetization on 2 with a χMT decrease of 12.82% can be observed. Finally, these hybrids can be used as long-term inkless and erasable print media. This work demonstrates the potential application of diphenyliodonium-based hybrids in some photo-sensitive functional materials. [ABSTRACT FROM AUTHOR]

We have developed a practical, general protocol for direct C–H azolation reactions of quinoxalin-2(1H)-ones by electro-oxidative cross-coupling. These mild reactions proceed under metal-, oxidant-, and reagent-free conditions to provide synthetically useful azolated quinoxalin-2(1H)-ones. Furthermore, the reactions can be carried out with a pencil lead as an electrode and a 3 V battery as a power source, revealing the remarkable flexibility of this protocol. [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]

A nickel-catalyzed intramolecular addition of aryl halides to 1,3-diketones was first developed. This desymmetrization reaction afforded polycyclic products bearing two tetrasubstituted centers with excellent diastereoselectivities and high yields. Moderate enantioselectivities were achieved in the presence of a chiral ligand. This transformation has great potential for the synthesis of polycyclic compounds including spiro[4,4,3,0] compounds. [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]

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 characters of σ- and π-holes of bromopentafluorobenzene (C6F5Br) enable it to interact with an electron-rich atom or group like pyridine which possesses an electron lone-pair N atom and a π ring. Theoretical studies of intermolecular interactions between C6F5Br and C5H5N have been carried out at the M06-2X/aug-cc-pVDZ level without and with the counterpoise method, together with single point calculations at M06-2X/TZVP, wB97-XD/aug-cc-pVDZ and CCSD(T)/aug-cc-pVDZ levels. The σ- and π-holes of C6F5Br exhibiting positive electrostatic potentials make these sites favorably interact with the N atom and the π ring of C5H5N with negative electrostatic potentials, leading to five different dimers connected by a σ-hole…n bond, a σ-hole…π bond or a π-hole…π bond. Their geometrical structures, characteristics, nature and spectroscopy behaviors were systematically investigated. EDA analyses reveal that the driving forces in these dimers are different. NCI, QTAIM and NBO analyses confirm the existence of intermolecular interactions formed viaσ- and π-holes of C6F5Br and the N atom and the π ring of C5H5N. The experimental IR and Raman spectra gave us important information about the formation of molecular complexes between C6F5Br and C5H5N. We expect that the results could provide valuable insights into the investigation of intermolecular interactions involving σ- and π-holes. [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]

Based on density functional theory and Berry curvature calculations, we predict that the p–p band inversion type quantum spin Hall effect (QSHE) can be realized in a series of two dimensional (2D) bilayer honeycomb TlMs (M = N, P, As, Sb), which can be effectively equivalent to a bilayer triangular lattice for low energy electrons. Further topological analysis reveals that the band inversion between p−z and px,y of the M atom contributes to the non-trivial topological nature of TlM. The band inversion is independent of spin–orbit coupling which is distinctive from conventional topological insulators (TIs). A tight binding model based on a triangular lattice is constructed to describe the QSH states in the systems. Besides the interesting 2D triangular lattice p–p type inversion for the topological mechanism, the maximal 550 meV local band gap (TlSb) and the tunable global band gap of the systems provide a new choice for a future room temperature quantum spin Hall insulator (QSHI). Considering the advance of the technology of van der Waals passivation, combination with hexagonal materials, such as h-BN, enables TlMs to show great potential for future 2D topological electronic devices. [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]

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]

Divergent cascade syntheses constitute a highly attractive and challenging area in synthetic chemistry, and can exhibit unexpected chemoselectivity. Herein, a Brønsted acid-controlled protocol is described for the efficient catalysis of two different reactions, namely acylation cascade- and [1+2+3]-type cyclization of enaminones and isatins for the concise synthesis of highly functionalized pyrrolo[3,4-c]quinolin-1-ones and spirooxindoles in the presence of carboxylic acids and KHSO4, respectively. The observed chemoselectivity was reasonably explained by trapping the intermediate α,β-unsaturated 2-oxindoles, and the source of the hydroxyl group, carbocation intermediate, and amination reaction were also evaluated. [ABSTRACT FROM AUTHOR]

Based on a comprehensive investigation including ab initio phonon and finite-temperature molecular dynamics calculations, we find that two-dimensional tricycle-shaped arsenene (T-As) is robust and even stable under high temperature. T-As is energetically comparable to previously reported chair-shaped arsenene (C-As) and more stable than stirrup-shaped arsenene (S-As). In contrast to C-As and S-As, the monolayer T-As is a direct band gap semiconductor with an energy gap of 1.377 eV. Our results indicate that the electronic structure of T-As can be effectively modulated by stacking, strain, and patterning, which shows great potential of T-As in future nano-electronics. Moreover, by absorbing H or F atoms on the surface of T-As along a specific direction, nanoribbons with desired edge type and even width can be obtained, which is suitable for the fabrication of nano-devices. [ABSTRACT FROM AUTHOR]

An osmotically swollen ammoniated MoS2 electrocatalyst for hydrogen evolution is developed via a simple hydrothermal route for the first time. The applied relatively high temperature and pressure promote the diffusion of NH4+ ions into MoS2 lamellar structures, leading to the formation of ammoniated MoS2 with remarkable lattice expansion. The insertion of NH4+ ions induces a great enhancement in the electrical conductivity of MoS2, resulting in an excellent activity for the hydrogen evolution reaction with a small Tafel slope of 45 mV dec−1, which is amongst the best recorded for MoS2-based catalysts, making it a very promising electrocatalyst to replace Pt-based ones. [ABSTRACT FROM AUTHOR]

A series of benzene derivatives with different substituents adsorbed on graphene was investigated using a density-functional tight-binding method with a dispersion correction. Compared to benzene, the derivative with either an electron-withdrawing or -donating substituent exhibits stronger physisorption. Moreover, the steric size of the substituent is important in determining the adsorption strength, while the direction and the number of H atoms in the substituent affect the electron transfer from graphene. NBO analysis reveals that the stereoelectronic effect of the conjugation between the substituent and the benzene ring strongly influences the π…π interaction region between the molecule and graphene. The findings can deepen the understanding of the interaction between an aromatic molecule and graphene as well as the corresponding adsorption mechanism. [ABSTRACT FROM AUTHOR]

A bulk transparent single-crystal of N-isopropylbenzylammonium dichloroacetate (N-IPBADC) with sizes of 15 × 15 × 10 mm3, which possesses switchable dielectric permittivities above room temperature, has been successfully grown by the slow solution cooling method. A reversible second-order solid-state phase transition at 366 K was confirmed by thermal analyses, including differential scanning calorimetry (DSC) and specific heat (Cp), dielectric measurements, variable-temperature single-crystal X-ray diffraction and powder X-ray diffraction (PXRD). In particular, order–disorder transformations of the dichloroacetate moieties in N-IPBADC from room temperature to high temperature phases have been revealed to induce the distinct dielectric anomaly along with dielectric anisotropic properties above room temperature, up to 366 K. The successful discovery of N-IPBADC would potentially pave a new way to explore new above room-temperature phase transition materials. [ABSTRACT FROM AUTHOR]

A novel switchable and tunable molecular dielectric material, diisopropylammonium trifluoromethanesulfonate (1), which undergoes two reversible second-order solid state phase transitions at 200 K (TcL) and 340 K (TcH) respectively, has been successfully synthesized and grown as bulk crystals. The differential scanning calorimetry (DSC) measurements, and dielectric and variable-temperature single-crystal X-ray diffraction studies confirmed the stepwise phase transitions. 1 exhibits a remarkable temperature-dependent dielectric behavior, which could be tuned through three distinctive states triggered by the temperature change. Temperature-dependent single crystal structural analyses of 1 reveal a collection of exceptionally distinct and synchronous molecular motions of both the cationic and anionic moieties in 1, and that the interesting stepwise ordering of cations and anions are mainly responsible for its switchable and tunable dielectric properties. All of this demonstrates its potential application as a switchable and tunable molecular dielectric material. [ABSTRACT FROM AUTHOR]

An organic dielectric relaxor, N-isopropylbenzylammonium tetrafluoroborate (1), with tunable dielectric properties between high and low dielectric states, has been successfully constructed through the prominent strategies of reversible structure transitions associated with ordering and reorientation of molecular motions. 1 undergoes an exceptional order–disorder solid state phase transition at 201 K, which was confirmed by the variable temperature single crystal X-ray diffraction analysis, thermal analysis and dielectric measurements. Owing to the ordering of the pendulum-like motion of methyl groups in the N-isopropylbenzylammonium (N-IPBA) cations and the reorientation of the molecular dipoles, 1 demonstrates a phase transition from a space group of C2/m at room temperature to C2/c at low temperature. Emphatically, the striking anisotropy of the dielectric response was investigated, revealing the crucial role of the ordering and orientation motions of N-IPBA cations. Moreover, the significant dielectric relaxation behaviour, attributed to the orientational polarization of the molecules’ dipoles, was observed and discussed. Such distinctive dielectric performances suggest that 1 might be a potential switchable relaxor-type dielectric material. [ABSTRACT FROM AUTHOR]

Our density functional theory (DFT)/time-dependent DFT calculations for the fluoride anion sensor, 5,7-dibromo-8-tert-butyldimethylsilyloxy-2-methylquinoline (DBM), suggested a different sensing mechanism from the experimentally proposed one (Chem. Commun., 2011, 47, 7098). Instead of the formation of fluoride–hydrogen-bond complex (DBMOHF) and excited-state proton transfer mechanism, the theoretical results predicted a sensing mechanism based on desilylation reaction and intramolecular charge transfer (ICT). The fluoride anion reacted with DBM and formed an anion (DBMO), with the ICT causing a red shift in the absorbance and emission spectra of the latter. The calculated vertical excitation energies in the ground and first excited states of both DBM and DBMO, as well as the calculated 1H NMR spectra, significantly reproduced the experimental measurements, providing additional proofs for our proposed sensing mechanism for DBM. [ABSTRACT FROM AUTHOR]

A series of ring-shaped molecular complexes formed by H3N, HF and XY (X = Cl, Br and Y = F, Cl, Br) have been investigated at the MP2/aug-cc-pVTZ level of theory. Their optimized geometry, stretching mode, and interaction energy have been obtained. We found that each complex possesses two red-shifted hydrogen bonds and one red-shifted halogen bond, and the two hydrogen bonds exhibit strong cooperative effects on the halogen bond. The cooperativity among the NH3FH, FHXY and H3NXY interactions leads to the formations of these complexes. The AIM analysis has been performed at the CCSD(T)/aug-cc-pVQZ level of theory to examine the topological characteristics at the bond critical point and at the ring critical point, confirming the coexistence of the two hydrogen bonds and one halogen bond for each complex. The NBO analysis carried out at the B3LYP/aug-cc-pVTZ level of theory demonstrates the effects of hyperconjugation, hybridization, and polarization coming into play during the hydrogen and halogen bonding formations processes, based on which a clockwise loop of charge transfer was discovered. The molecular electrostatic potential has been employed to explore the formation mechanisms of these molecular complexes. [ABSTRACT FROM AUTHOR]

Correction for ‘Insights into the unexpected chemoselectivity in Brønsted acid catalyzed cyclization of isatins with enaminones: convenient synthesis of pyrrolo[3,4-c]quinolin-1-ones and spirooxindoles’ by Hui Xu et al., Chem. Commun., 2016, 52, 8002–8005. [ABSTRACT FROM AUTHOR]