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Borazine is a well-established precursor molecule for the growth of hexagonal boron nitride (h-BN) via chemical vapor deposition on metal substrates. To understand the formation of the h-BN/Rh(111) moiré from borazine on a molecular level, we investigated the low-temperature adsorption and thermally induced on-surface reaction of borazine on Rh(111) in situ using synchrotron radiation-based high-resolution x-ray photoelectron spectroscopy (XPS), temperature-programmed XPS, and near-edge x-ray absorption fine structure measurements. We find that borazine adsorbs mainly as an intact molecule and have identified a flat-lying adsorption geometry. Borazine multilayers are observed to desorb below 200 K. Starting at about 300 K, dehydrogenation of the remaining borazine and borazine fragments takes place, and disordered boron nitride starts to grow. Above 600 K, the formation of the h-BN sets in. Finally, at 1100 K, the conversion to h-BN is complete. The h-BN formed by deposition and post-annealing was compared to the h-BN grown by an established procedure, proving the successful preparation of the desired two-dimensional material. [ABSTRACT FROM AUTHOR]

Borazine-doped π-conjugated frameworks have significantly contributed to advancing the application of boron–nitrogen-doped organic materials. However, the challenging synthetic procedure has imposed limits on progress. In the case of hexaaryl-substituted borazines (HABs), the instability of B,B′,B′′-trichloro-N,N′,N′′-triarylborazine (TCB) due to the high reactivity of the boron site necessitates the synthesis and nucleophilic substitution of the chlorinated borazine under strict avoidance of moisture and oxygen to obtain HABs. Moving toward an ideal more sustainable synthesis, the first continuous flow process for the synthesis of HABs has been developed, enabling fast and safe boron arylation. The new process facilitates the neutralization and cleanup of the TCB solution from acidic by-products by utilizing an inorganic scavenger. BY making use of bio-derived 2-MeTHF as reaction medium, the common wasteful isolation procedure of HABs can be avoided, thus allowing not only simplifying the preparation of substituted borazines in high yields but also minimizing its environmental impact and improving its safety profile. [ABSTRACT FROM AUTHOR]

It is shown by tiling that only three out of the thirteen title molecules are planar. Using our recent concept of quasi-molecule ('tile') or its generalisation, all participating tiles have been here optimised in a few spin-states both at the DFT level with the B3LYP and M06-2X functionals, and using the CCSD(T) method. While borazine ( $ 1,4,6-{\rm B}_3{\rm N}_3{\rm H}_6 $ 1 , 4 , 6 − B 3 N 3 H 6 ) was synthesised in the forties of the past century, its next up-lying planar isomer ( $ 1,3,4-{\rm B}_3{\rm N}_3{\rm H}_6 $ 1 , 3 , 4 − B 3 N 3 H 6 or $ {\rm BHNHNHBHBHNH} $ BHNHNHBHBHNH ) was not. Quasi-tetratomic tiles are then shown to be shape-determining while 5-body terms and beyond are shape-preserving. The need to bring the notion of planarity as a probabilistic outcome is also examined, and the concept of planarity likelihood ratio (index) introduced. As for the above borazine isomers, this index is also predicted to be unit for $ 1,4-{\rm B}_4{\rm N}_2{\rm H}_6 $ 1 , 4 − B 4 N 2 H 6 , a result that is corroborated upon its optimisation at DFT/B3LYP/AVTZ level but not with M06-2X by which it is predicted as quasi-planar. Nevertheless, recent work with a derivative of diazatetraborinine where all atoms are bonded to substituent atoms or groups of atoms confirms the planarity of the $ {\rm B}_4{\rm N}_2 $ B 4 N 2 ring. Such a result is further corroborated at the gold-standard CCSD(T) level. Although planarity is also predicted for $ {\rm B}_6{\rm H}_6 $ B 6 H 6 , DFT and CCSD(T) frequency calculations suggest it to be likely a saddle point. [ABSTRACT FROM AUTHOR]

We have defined a procedure for the late‐stage functionalization of aryl borazines to facilitate the synthesis of a diverse array of borazine derivatives with varying substitution patterns, paving the way for further exploration of the field. More in detail, we have studied and disclosed a simple iodination procedure that could be applied to several differently substituted substrates (1 a–i) with mostly good to excellent yields (47–96%). The representative iodinated compounds 2 b and 2 e, were utilized to test their use in further representative functionalization steps such as cyanation, Heck, and Sonogashira reactions. All products 3 a–e were obtained in satisfactory good to very good yields considering the multiple (three or six times) concomitant reactions. [ABSTRACT FROM AUTHOR]

The interaction of borazine with metal supports and the concomitant surface chemistry play important roles in the synthesis of hexagonal boron nitride and the assembly of BN‐doped carbon nanostructures, thus making adsorbed borazine an intriguing model system. Herein, the first real space characterization of individual borazine molecules and highly ordered borazine self‐assemblies on solid supports, combining scanning tunneling microscopy (STM), scanning tunneling spectroscopy, X‐ray photoelectron spectroscopy, and complementary density functional theory modeling is reported. Specifically, a weak, nondissociative adsorption of borazine with the ring aligned in parallel to the surface plane is observed on Ag(111) upon low temperature deposition. Borazine is found to favor hollow adsorption sites, which guide the assembly of intricate borazine assemblies including a porous, chiral honeycomb‐like network, and dense‐packed monolayer films. Additionally, a modification of the borazine adsorption configuration by STM‐based manipulation is demonstrated. Dehydrogenation of individual molecules by voltages pulses yields an upright standing borazine fragment bound via B to Ag. This study thus provides a comprehensive, single‐molecule level characterization of borazine adsorption and surface chemistry on a characteristic coinage metal support and may serve as a reference for advanced low‐dimensional materials based on functionalized borazines or including BN units as dopants. [ABSTRACT FROM AUTHOR]

Dehydrogenation of ammonia borane to well-defined products is an important but challenging reaction. A dinuclear ruthenium complex with a Ru–Ru bond bearing a diazadiene (dad) unit and olefins as non-innocent ligands catalyzes the highly selective formation of conjugated polycondensed borazine oligomers (BxNxHy), predominantly B21N21H18, the BN analogue of superbenzene. [ABSTRACT FROM AUTHOR]

Boron-doped organic compounds display unique properties as a result of the presence of an empty p orbital on boron and the ability to switch between a trigonal planar and a tetrahedral geometry. In recent years, they have found several applications not only as synthetic reagents, e.g., in the Suzuki–Miyaura reaction, but also as pharmaceuticals and as specialized materials due to their optical and electronic properties. Some boron compounds may exist as atropisomers, and these rotamers may have different properties according to their sense of rotation. Synthetic strategies to separate them and, more recently, to obtain them in an asymmetric manner are becoming popular. In this review, we survey the literature on this emerging field of research. [ABSTRACT FROM AUTHOR]

The title compound, alternatively known as benzodiazaborole trimer, C18H15B3N6·2C3H6O, at 100 K crystallizes in the triclinic system, space group P\overline{1}. The structure displays N—H...O hydrogen bonding connecting the main molecule with the crystallization solvent. Disorder of the main molecule is observed with occupancy factors refined to 0.8922 (14):0.1078 (14). The packing of the crystal shows a parallel-displaced atom-centered orientation with 3.30 (2) Å between the planes of the rings. In the solid state, the title compound is linked with weak C—H...π interactions, which is supported by Hirshfeld surface analysis.

Alkali atom-doped hexalithioborazine (B3N3Li6-M) as a novel class of super-alkali complex has been investigated for their exceptionally high first-order and second-order electrical responsive properties. The stability of resulting complexes, B3N3Li6-M (M = Li, Na, and K), is confirmed by the ADMP simulation and the negative values of thermodynamic parameters such as binding energy (∆Eb) and Gibbs free energy (∆G). The relationship between aromaticity (NICS) and first hyperpolarizability of B3N3Li6-M follows linear relationship. Diffuse electron cloud around the central ring and doped alkali metal in the HOMO of B3N3Li6-M complexes has been attributed to the charge transfer from peripheral Li to the dopant metal (M) atom. The dipole moment of B3N3Li6-M varies between 0.507 D (M = Na) and 1.608 D (M = Li) due to charge transfer in these complexes. The mean polarizabilities (αav) of B3N3Li6-M ranging from 573.08 to 1598.86 a.u are observed. Exceptionally high value of second-order NLO parameter (βav = 5.133 × 105 a.u and βHRS = 2.166 × 106 a.u) are observed in case of Li-doped B3N3Li6 in this series. Thus, the first hyperpolarizability (βav and βHRS) values of the complexes produced by the interactions between alkali metal atoms (M) and B3N3Li6 are strong enough to demonstrate as potential second-order NLO materials. [ABSTRACT FROM AUTHOR]

The past decade has marked a renewed interest in borazines and BN‐doped polycyclic aromatic hydrocarbons. This is predominantly because of new advances that have highlighted their potential in various applications, including gas separation and storage, organic (opto)electronics, catalysis, and as supramolecular systems. This review gives a critical overview of the most significant approaches to the synthesis of (substituted) B3N3 motifs and focuses on the discussion of those borazine‐doped carbon structures that have been developed for potential use in materials science applications. [ABSTRACT FROM AUTHOR]

The title compound, alternatively known as benzodiazaborole trimer, C18H15B3N6⋅2C3H6O, at 100 K crystallizes in the triclinic system, space group P1. The structure displays N--H⋯O hydrogen bonding connecting the main molecule with the crystallization solvent. Disorder of the main molecule is observed with occupancy factors refined to 0.8922 (14):0.1078 (14). The packing of the crystal shows a parallel-displaced atom-centered orientation with 3.30 (2) Å between the planes of the rings. In the solid state, the title compound is linked with weak C--H⋯π interactions, which is supported by Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

Abstract The interaction of borazine with metal supports and the concomitant surface chemistry play important roles in the synthesis of hexagonal boron nitride and the assembly of BN‐doped carbon nanostructures, thus making adsorbed borazine an intriguing model system. Herein, the first real space characterization of individual borazine molecules and highly ordered borazine self‐assemblies on solid supports, combining scanning tunneling microscopy (STM), scanning tunneling spectroscopy, X‐ray photoelectron spectroscopy, and complementary density functional theory modeling is reported. Specifically, a weak, nondissociative adsorption of borazine with the ring aligned in parallel to the surface plane is observed on Ag(111) upon low temperature deposition. Borazine is found to favor hollow adsorption sites, which guide the assembly of intricate borazine assemblies including a porous, chiral honeycomb‐like network, and dense‐packed monolayer films. Additionally, a modification of the borazine adsorption configuration by STM‐based manipulation is demonstrated. Dehydrogenation of individual molecules by voltages pulses yields an upright standing borazine fragment bound via B to Ag. This study thus provides a comprehensive, single‐molecule level characterization of borazine adsorption and surface chemistry on a characteristic coinage metal support and may serve as a reference for advanced low‐dimensional materials based on functionalized borazines or including BN units as dopants.

The chemical stability and the low‐lying singlet and triplet excited states of BN‐n‐acenes (n = 1–7) were studied using single reference and multireference methodologies. From the calculations, descriptors such as the singlet‐triplet splitting, the natural orbital (NO) occupations and aromaticity indexes are used to provide structural and energetic analysis. The boron and nitrogen atoms form an isoelectronic pair of two carbon atoms, which was used for the complete substitution of these units in the acene series. The structural analysis confirms the effects originated from the insertion of a uniform pattern of electronegativity difference within the molecular systems. The covalent bonds tend to be strongly polarized which does not happen in the case of a carbon‐only framework. This effect leads to a charge transfer between neighbor atoms resulting in a more strengthened structure, keeping the aromaticity roughly constant along the chain. The singlet‐triplet splitting also agrees with this stability trend, maintaining a consistent gap value for all molecules. The BN‐n‐acenes molecules possess a ground state with monoconfigurational character indicating their electronic stability. The low‐lying singlet excited states have charge transfer character, which proceeds from nitrogen to boron. [ABSTRACT FROM AUTHOR]

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2D boron nitride (2D-BN) was synthesized by gas-source molecular beam epitaxy on polycrystalline and monocrystalline Ni substrates using gaseous borazine and active nitrogen generated by a remote plasma source. The excess of nitrogen atoms allows to overcome the thickness self-limitation active on Ni when using borazine alone. The nucleation density and the shape of the 2D-BN domains are clearly related to the Ni substrate preparation and to the growth parameters. Based on spatially-resolved photoemission spectroscopy and on the detection of the π plasmon peak, we discuss the origin of the N1s and B1s components and their relationship with an electronic coupling at the interface. After optimization of the growth parameters, a full 2D-BN coverage is obtained, although the material thickness is not evenly distributed. The 2D-BN presents a granular structure on (111) oriented Ni grains, showing a rather poor cristallographic quality. On the contrary, high quality 2D-BN is found on (101) and (001) Ni grains, where triangular islands are observed whose lateral size is limited to ∼20 μ m. [ABSTRACT FROM AUTHOR]

Boron-doped organic compounds display unique properties as a result of the presence of an empty p orbital on boron and the ability to switch between a trigonal planar and a tetrahedral geometry. In recent years, they have found several applications not only as synthetic reagents, e.g., in the Suzuki–Miyaura reaction, but also as pharmaceuticals and as specialized materials due to their optical and electronic properties. Some boron compounds may exist as atropisomers, and these rotamers may have different properties according to their sense of rotation. Synthetic strategies to separate them and, more recently, to obtain them in an asymmetric manner are becoming popular. In this review, we survey the literature on this emerging field of research.

Together with borazine, ammonia borane is a prominent precursor molecule for the formation of hexagonal boron nitride, which is of high interest as a 2D-material and graphene analog. Ammonia borane is also a possible solid hydrogen carrier for renewable energies with high storage density. Using X-ray photoelectron spectroscopy and temperature-programmed desorption, we investigated low-temperature adsorption and dehydrogenation during heating of borazine and ammonia borane on Ni(111) to form h-BN. For borazine, we observe the formation of disordered boron nitride above 300 K, which starts to form hexagonal boron nitride above 600 K. Ammonia borane shows multiple dehydrogenation steps at the boron and nitrogen atoms up to 300 K. This results in various BHxNHy species, including borazine-like intermediates, before the formation of disordered boron nitride and finally hexagonal boron nitride, analogous to the borazine decomposition. [ABSTRACT FROM AUTHOR]

The growth of hexagonal boron nitride (hBN) on epitaxial Ge(001)/Si substrates via high-vacuum chemical vapor deposition from borazine is investigated for the first time in a systematic manner. The influences of the process pressure and growth temperature in the range of 10−7–10−3 mbar and 900–980 °C, respectively, are evaluated with respect to morphology, growth rate, and crystalline quality of the hBN films. At 900 °C, nanocrystalline hBN films with a lateral crystallite size of ~2–3 nm are obtained and confirmed by high-resolution transmission electron microscopy images. X-ray photoelectron spectroscopy confirms an atomic N:B ratio of 1 ± 0.1. A three-dimensional growth mode is observed by atomic force microscopy. Increasing the process pressure in the reactor mainly affects the growth rate, with only slight effects on crystalline quality and none on the principle growth mode. Growth of hBN at 980 °C increases the average crystallite size and leads to the formation of 3–10 well-oriented, vertically stacked layers of hBN on the Ge surface. Exploratory ab initio density functional theory simulations indicate that hBN edges are saturated by hydrogen, and it is proposed that partial de-saturation by H radicals produced on hot parts of the set-up is responsible for the growth. [ABSTRACT FROM AUTHOR]

The on-surface synthesis strategy has emerged as a promising route for fabricating well-defined two-dimensional (2D) BN-substituted carbon nanomaterials with tunable electronic properties. This approach relies on specially designed precursors and requires a thorough understanding of the on-surface reaction pathways. It promises precise structural control at the atomic scale, thus complementing chemical vapor deposition (CVD). In this study, we investigated a novel heteroatomic precursor, tetrabromoborazine, which incorporates a BN core and an OH group, on Ag(111) using low temperature scanning tunnelling microscopy/spectroscopy (LT-STM/STS) and X-ray photoelectron spectroscopy (XPS). Through sequential temperature-induced reactions involving dehalogenation and dehydrogenation, distinct tetrabromoborazine derivatives were produced as reaction intermediates, leading to the formation of specific self-assemblies. Notably, the resulting intricate supramolecular structures include a chiral kagomé lattice composed of molecular dimers exhibiting a unique electronic signature. The final product obtained was a random covalent carbon network with BN-substitution and embedded oxygen heteroatoms. Our study offers valuable insights into the significance of the structure and functionalization of BN precursors in temperature-induced on-surface reactions, which can help future rational precursor design. Additionally, it introduces complex surface architectures that offer a high areal density of borazine cores., (© 2024 Wiley‐VCH GmbH.)

Given the wide array of current applications of borazine-based materials, synthetic access to these compounds is of importance. This review summarizes the many ways of preparing borazines and its carbo-substituted analogues. In addition, the functionalization of borazines is covered. The synthesis of molecules incorporating more than one borazine units as well as aspects of unsymmetrically substituted borazines are not included. The literature has been covered comprehensively until the end of 2020. 1 Introduction: Structure and Properties of Borazine 2 Synthesis of Parent Borazine 3 Synthesis of N -Substituted Borazines 4 Synthesis of B -Halo/ B -Halo- N -Substituted Borazines 5 Synthesis of B -Substituted Borazines 6 Synthesis of Polycyclic Borazines Containing One Borazine Ring 7 Modifications or Hydrolysis of the Borazine Ring 8 Borazine Metal Complexes 9 Outlook and Conclusion [ABSTRACT FROM AUTHOR]

Activation of small molecules is one of the important research topics for last decade. Activation of nitrogen is one among the important small molecule. This work presents a DFT study of the adsorption properties of nitrogen molecule over group 8 metal-borazine complex. Using B3LYP theory and 6-31G*/LANL2DZ basis sets, the different mode of adsorption of dinitrogen over the metal-borazine complex has been studied. In all the case, dinitrogen has adsorbed over the metal-borazine complex without undergoing any deformation and decomposition. Vibrational analysis, NPA and FMOs analysis afford significant understanding into their bonding and reactivity pattern. All the complexes show very strong binding towards dinitrogen and lead to activation of nitrogen molecule with less energy barrier. It has been observed that dinitrogen is highly activated in the case of Os-complex. The results show that group 8 metal-borazine complexes are a potential nitrogen trapper and good choice of complexes for activating the nitrogen molecule. [ABSTRACT FROM AUTHOR]

Elastic waves have emerged as a paradigm of condensed matter physics since many dynamical effects of the latter can be emulated with these waves. Molecular Π-orbitals are of great interest in this area because they play a key role in the electronic transport of 2D materials and aromatic molecules such as benzene and borazine. In this work, we show the design, construction and characterization of an elastic, artificial borazine structure that emulates the Π-orbitals of borazine. The elastic structure consists of hexagonal resonators that act as artificial elastic atoms coupled to each other through finite phononic crystals that in turn act as artificial Π bonds. When the resonant frequency of an artificial atom falls within the gap of the phononic crystal, the vibrations are trapped in the artificial atom and interact weakly with neighboring artificial atoms through evanescent Bloch waves. Thus, a tight-binding regime for elastic waves emerges. Here, these ideas are applied to emulate the Π-orbitals of borazine. The design relies on extensive finite element numerical simulations. The experimental results show an excellent agreement with both, the tight-binding formalism and the numerical results. [ABSTRACT FROM AUTHOR]

Borazine is isoelectronic with benzene and is popularly referred to as inorganic benzene. The study of non-covalent interactions with borazine and comparison with its organic counterpart promises to show interesting similarities and differences. The motivation of the present study of the borazine-water interaction, for the first time, stems from such interesting possibilities. Hydrogen-bonded complexes of borazine and water were studied using matrix isolation infrared spectroscopy and quantum chemical calculations. Computations were performed at M06-2X and MP2 levels of theory using 6-311++G(d,p) and aug-cc-pVDZ basis sets. At both the levels of theory, the complex involving an N--H···O interaction, where the N--H of borazine serves as the proton donor to the oxygen of water was found to be the global minimum, in contrast to the benzene-water system, which showed an H--π interaction. The experimentally observed infrared spectra of the complexes corroborated well with our computations for the complex corresponding to the global minimum. In addition to the global minimum, our computations also located two local minima on the borazine-water potential energy surface. Of the two local minima, one corresponded to a structure where the water was the proton donor to the nitrogen of borazine, approaching the borazine ring from above the plane of the ring; a structure that resembled the global minimum in the benzene-water H--π complex. The second local minimum corresponded to an interaction of the oxygen of water with the boron of borazine, which can be termed as the boron bond. Clearly the borazine-water system presents a richer landscape than the benzene-water system. [ABSTRACT FROM AUTHOR]

The growth of hexagonal boron nitride (hBN) on epitaxial Ge(001)/Si substrates via high-vacuum chemical vapor deposition from borazine is investigated for the first time in a systematic manner. The influences of the process pressure and growth temperature in the range of 10−7–10−3 mbar and 900–980 °C, respectively, are evaluated with respect to morphology, growth rate, and crystalline quality of the hBN films. At 900 °C, nanocrystalline hBN films with a lateral crystallite size of ~2–3 nm are obtained and confirmed by high-resolution transmission electron microscopy images. X-ray photoelectron spectroscopy confirms an atomic N:B ratio of 1 ± 0.1. A three-dimensional growth mode is observed by atomic force microscopy. Increasing the process pressure in the reactor mainly affects the growth rate, with only slight effects on crystalline quality and none on the principle growth mode. Growth of hBN at 980 °C increases the average crystallite size and leads to the formation of 3–10 well-oriented, vertically stacked layers of hBN on the Ge surface. Exploratory ab initio density functional theory simulations indicate that hBN edges are saturated by hydrogen, and it is proposed that partial de-saturation by H radicals produced on hot parts of the set-up is responsible for the growth.

A number of superalkali (M3O / M3S; M = Li, Na, K)-doped borazine and hexalithio borazine complexes are considered for the theoretical study of their electronic structure and quadratic polarizability. Electron-rich O/S atom of superalkali species remains very close to one boron atom of the ring through non-covalent interaction. The first-hyperpolarizability increases rather significantly upon superalkali doping. The chosen complexes possess diffuse excess electron which is located on the superpalkali moiety of borazine complexes and at the ring site of lithiated borazines. First-hyperpolarizability of M3O(S)@B3N3Li6 complexes are significantly larger than that of the corresponding M3O(S)@B3N3H6 complexes. The magnitude of first-hyperpolarizability of Li3S@B3N3Li6 is larger than that of Li3S@B3N3H6 by about three orders of magnitude. [ABSTRACT FROM AUTHOR]

Building on the MOF approach to prepare porous materials, herein we report the engineering of porous BN‐doped materials using tricarboxylic hexaarylborazine ligands, which are laterally decorated with functional groups at the full‐carbon 'inner shell'. Whilst an open porous 3D entangled structure could be obtained from the double interpenetration of two identical metal frameworks derived from the methyl substituted borazine, the chlorine‐functionalised linker undergoes formation of a porous layered 2D honeycomb structure, as shown by single‐crystal X‐ray diffraction analysis. In this architecture, the borazine cores are rotated by 60° in alternating layers, thus generating large rhombohedral channels running perpendicular to the planes of the networks. An analogous unsubstituted full‐carbon metal framework was synthesised for comparison. The resulting MOF revealed a crystalline 3D entangled porous structure, composed by three mutually interpenetrating networks, hence denser than those obtained from the borazine linkers. Their microporosity and CO2 uptake were investigated, with the porous 3D BN‐MOF entangled structure exhibiting a large apparent BET specific surface area (1091 m2 g−1) and significant CO2 reversible adsorption (3.31 mmol g−1) at 1 bar and 273 K. [ABSTRACT FROM AUTHOR]

The geometrical structures of neutral and anionic Com(borazine)n (m = 1, 2; n = 1–3) complexes have been determined by using density functional theory. The results indicate that most of the ground state structures for the complexes are similar to those of Com(benzene)n, which might because borazine is isoelectronic and isostructural to benzene. The frontier molecular orbitals (FMOs) analyses show that their FMOs mainly arise from the 3d/4s electrons of cobalt atoms and the weak π-cloud of borazine molecule. Furthermore, the magnetic moments of complexes were studied and the results revealed that the Co atoms carry most of the magnetic moments. Comparing with the magnetic moment of a free Co atom (3.0μB), the magnetic moments of Co atom in most of Com(borazine)n0/- complexes are significantly reduced and even quenched except that the Co(borazine) remains unchanged. More importantly, there is a transition FM-to-AFM between neutral and anionic Co2(borazine)2. Finally, natural population analyses were performed to insightfully explore the reliable electronic structure properties. [ABSTRACT FROM AUTHOR]

Benzene, a common aromatic compound, can be converted into an unstable antiaromatic 8π‐electron intermediate through two‐electron reduction. However, as an isoelectronic equivalent of benzene, borazine (B3N3Ph6), having weak aromaticity, undergoes a totally different two‐electron reduction to afford (B3N3R6)2− homoaromatic compounds. Reported here is the synthesis of homoaromatic (B3N3Ph6)2− by the reduction of B3N3Ph6 with either potassium or rubidium in the presence of 18‐crown‐6 ether. Theoretical investigations illustrate that two electrons delocalize over the three boron atoms in (B3N3Ph6)2−, which is formed by the geometric and orbital reorganization and exhibits (π,σ)‐mixed homoaromaticity. Moreover, (B3N3Ph6)2− can act as a robust 2e reductant for unsaturated compounds, such as anthracene, chalcone, and tanshinones. This 2e reduction is of high efficiency and selectivity, proceeds under mild reaction conditions, and can regenerate neutral borazine. [ABSTRACT FROM AUTHOR]

In this work, a comprehensive account of the authors' synthetic efforts to prepare borazino‐doped hexabenzocoronenes by using the Friedel–Crafts‐type electrophilic aromatic substitution is reported. Hexafluoro‐functionalized aryl borazines, bearing an ortho fluoride leaving group on each of the N‐ and B‐aryl rings, was shown to lead to cascade‐type electrophilic aromatic substitution events in the stepwise C−C bond formation, giving higher yields of borazinocoronenes than those obtained with borazine precursors bearing fluoride leaving groups at the ortho positions of the B‐aryl substituents. By using this pathway, an unprecedented boroxadizine‐doped PAH featuring a gulf‐type periphery could be isolated, and its structure proven by single‐crystal X‐ray diffraction analysis. Mechanistic studies on the stepwise Friedel–Crafts‐type cyclization suggest that the mechanism of the planarization reaction proceeds through extension of the π system. To appraise the doping effect of the boroxadizine unit on the optoelectronic properties of topology‐equivalent molecular graphenes, the all‐carbon and pyrylium PAH analogues, all featuring a gulf‐type periphery, were also prepared. As already shown for the borazino‐doped hexabenzocoronene, the replacement of the central benzene ring by its B3N2O congener widens the HOMO–LUMO gap and dramatically enhances the fluorescence quantum yield. [ABSTRACT FROM AUTHOR]

A theoretical study on the intermolecular dihydrogen bonding (DHB) of ground state B3N3H6···HM (Li, Na, and K) complexes were investigated by B3LYP and MP2 methods with 6-311++G** basis set. Thermodynamic parameters (entropy, enthalpy, heat capacity and Gibbs free energy) of the complexes were calculated at different temperatures in the gas phase. The vibrational analysis of N–H···H–M DHB bond formation reveals that the calculated N–H and M–H stretching frequencies undergo red and blue shifts, respectively. The calculated interaction energies correlate well with the geometrical parameters wherein the shortest H···H intermolecular distance is obtained for B3N3H6···HK complex. The chemical shift of 1H, 11B and 15N NMR predict large variation for B3N3H6···HK complex which has large protonic hydrogen than the hydridic hydrogen. Furthermore, natural bond orbital and quantum theory of atoms in molecule analyses were carried out to explore the non-covalent interaction along with the molecular electrostatic potential to predict the reactive sites of electrophilic and nucleophilic attack. [ABSTRACT FROM AUTHOR]

[Display omitted] • This research is the first systematic investigation of BN-helicenes. • BN-[ n ]helicenes with ring number n ranging from 4 to 12 have been studied. • BN-helicenes showed unique aromaticity compared with carbohelicenes. • BN-helicenes exhibited larger HOMO-LUMO gaps and shorter UV-vis absorptions. In this study, we have demonstrated a new type of helicene, the boron-nitrogen helicenes, the isostructural and isoelectronic homolog of conventional carbohelicenes, by DFT theoretical calculations. We have systematically investigated the geometry, electronic characteristics, enantiomerization, aromaticity, as well as absorption and electronic circular dichroism properties of BN-[n]helicenes, where the ring number n varies from 4 to 12. Notably, the substitution of the original benzene core with a borazine mother core has endowed these BN-helicenes with distinctive properties different from those of conventional carbohelicenes. Specifically, they exhibit atypical aromaticity and exhibit a pronounced electronic circular dichroism behavior. [ABSTRACT FROM AUTHOR]

The title compound, alternatively known as benzodi-aza-borole trimer, C 18 H 15 B 3 N 6 ·2C 3 H 6 O, at 100 K crystallizes in the triclinic system, space group P . The structure displays N-H⋯O hydrogen bonding connecting the main mol-ecule with the crystallization solvent. Disorder of the main mol-ecule is observed with occupancy factors refined to 0.8922 (14):0.1078 (14). The packing of the crystal shows a parallel-displaced atom-centered orientation with 3.30 (2) Å between the planes of the rings. In the solid state, the title compound is linked with weak C-H⋯π inter-actions, which is supported by Hirshfeld surface analysis., (© Streeter et al. 2023.)

We found that oxidized Cu nanoparticles can catalyze the growth of boron nitride nanotubes from borazine via plasma-assisted chemical vapor deposition. The Raman spectra suggest that the formation of thin-walled nanotubes show a radial breathing mode vibration. The presence of oxygen in the plasma environment was necessary for the growth of the nanotubes, and a part of the nanotubes had a core shell structure with a cupper species inside it. In atomic resolution transmission electron microscope (TEM) images, Cu2O was found at the interface between the Cu-core and turbostratic BN-shell. The growth mechanism seemed different from that of carbon nanotube core-shell structures. Therefore, we pointed out the important role of the dynamic morphological change in the Cu2O-Cu system.

We present the research findings of the DOE-funded Hydrogen Storage Engineering Center of Excellence (HSECoE) related to liquid-phase and slurry-phase chemical hydrogen storage media and their potential as future hydrogen storage media for automotive applications. Chemical hydrogen storage media other than neat liquid compositions will prove difficult to meet the DOE system level targets. Solid- and slurry-phase chemical hydrogen storage media requiring off-board regeneration are impractical and highly unlikely to be implemented for automotive applications because of the formidable task of developing solid- or slurry-phase transport systems that are commercially reliable and economical throughout the entire life cycle of the fuel. Additionally, the regeneration cost and efficiency of chemical hydrogen storage media is currently the single most prohibitive barrier to implementing chemical hydrogen storage media. Ideally, neat liquid-phase chemical hydrogen storage media with net-usable gravimetric hydrogen capacities of greater than 7.8 wt% are projected to meet the 2017 DOE system level gravimetric and volumetric targets. The research presented herein is a collection of research findings that do not in and of themselves warrant a dedicated manuscript. However, the collection of results do, in fact, highlight the engineering challenges and short-comings in scaling up and demonstrating fluid-phase ammonia borane and alane compositions that all future materials researchers working in hydrogen storage should be aware of.

Borazines are used in chemical vapor deposition processes to produce hybrid graphene–boron nitride nanostructures. As the knowledge on the mechanism of borazine formation is scarce, we studied the mechanism of formation of B,B′,B′′-trichloro-N,N′,N′′-tri(p-fluorophenyl)borazine (3a) from p-fluoroaniline and boron trichloride employing NMR spectroscopy, X-ray single crystal structure analysis, trapping experiments, and computational chemistry methods up to the coupled cluster CCSD(T) level of theory. These studies suggest the initial formation of the 1 : 1 adduct 1a (ArNH2BCl3, Ar = 4-fluorophenyl) with a dative B–N bond that could be fully characterized including single crystal X-ray diffraction. Adduct 1a undergoes unimolecular hydrogen chloride elimination with a first-order rate constant of k1 = 3.03(7) × 10−2 min−1 in toluene at 100 °C. This rate constant is in very good agreement with the one derived (k1 = 3.18 × 10−2 min−1) from computed activation parameters (ΔH‡373.15 = 28.1 kcal mol−1, ΔS‡373.15 = 1.56 eu, ΔG‡373.15 = 27.6 kcal mol−1). The product of the first hydrogen chloride evolution is anilinodichloroborane ArNHBCl2 (2a). Compound 2a cannot be isolated in a pure form due to instability, but its presence as a transient reactive intermediate can be derived from NMR spectroscopy. Reactive intermediates other than anilinodichloroborane cannot be assigned by NMR spectroscopy. We propose that the mechanism of formation of borazine 3a involves the reaction of 2a with 4-fluoroaniline as the rate determining step. [ABSTRACT FROM AUTHOR]

The temperature dependence of vapor pressure over liquid and solid borazine has been measured by static tensiometry method with a membrane null-manometer at 200–259 K. Gas-phase heat-induced decomposition of borazine in its unsaturated vapor has been studied over the 373–473 K range. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitrite (hBN) is an attractive material for many applications such as in electronics as a complement to graphene, in anti-oxidation coatings, light emitters, etc. However, the synthesis of high-quality hBN at cost-effective conditions is still a great challenge. Thus, this work reports on the synthesis of large-area and crystalline hBN nanosheets via the modified polymer derived ceramics (PDCs) process. The addition of both the BaF2 and Li3N, as melting-point reduction and crystallization agents, respectively, led to the production of hBN powders with excellent physicochemical properties at relatively low temperatures and atmospheric pressure conditions. For instance, XRD, Raman, and XPS data revealed improved crystallinity and quality at a decreased formation temperature of 1200 °C upon the addition of 5 wt% of BaF2. Moreover, morphological determination illustrated the formation of multi-layered nanocrystalline and well-defined shaped hBN powders with crystal sizes of 2.74−8.41 ± 0.71 µm in diameter. Despite the compromised thermal stability, as shown by the ease of oxidation at high temperatures, this work paves way for the production of large-scale and high-quality hBN crystals at a relatively low temperature and atmospheric pressure conditions.

Boron nitride (BN) is a III-V compound which is the focus of important research since its discovery in the early 19th century. BN is electronic to carbon and thus, in the same way that carbon exists as graphite, BN exists in the hexagonal phase. The latter offers an unusual combination of properties that cannot be found in any other ceramics. However, these properties closely depend on the synthesis processes. This review states the recent developments in the preparation of BN through the chemistry, shaping and ceramic conversion of borazine derivatives. This concept denoted as Polymer-Derived Ceramics (PDCs) route allows tailoring the chemistry of precursors to elaborate complex BN shapes which cannot be obtained by conventional process. The effect of the chemistry of the molecular precursors, i.e., borazine and trichloroborazine, and their polymeric derivatives i.e., polyborazylene and poly[tri(methylamino)borazine], in which the specific functional groups and structural motifs determine the shaping potential by conventional liquid-phase process and plastic-forming techniques is discussed. Nanotubes, nano-fibers, coatings, monoliths and fiber-reinforced matrix composites are especially described. This leads to materials which are of significant engineering interest.

Pillar[5]arene and its derivatives act as useful complexing agents and find utility in various fields of chemistry. Effects of doping of borazine unit in pillar[5]arene with respect to its geometry, reactivity and spectroscopic properties are discussed in the light of density functional theory and density functional reactivity theory. Reactivity parameters namely energy of the HOMO, global hardness and chemical potential are used to explain the reactivity of the undoped and doped pillar[5]arene. Aromaticity of the chosen molecule is determined by Nucleus Independent Chemical Shift (NICS) calculations. Absorption spectra of the chosen molecules are analyzed using time dependent density functional theory. Results suggest enhanced stability of pillar[5]arene system upon doping with of borazine unit. Blue shifts in absorption spectra of pillar[5]arene systems upon such doping are also evident which is remarkable from the viewpoint of its opto-electronic utility. [ABSTRACT FROM AUTHOR]

The first examples of group 13 element containing pyridinophanes have been assembled using heteroatom N–E–N bridges (E = B, Al). The presence of B and Al as acceptor atoms in the bridges and their coordination with pyridine nitrogen has a very strong influence on the conformational rigidity of the pyridinophanes. [ABSTRACT FROM AUTHOR]