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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.

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]

Heterocyclen, die Elemente der Gruppen 13 und 15 enthalten, wie z. B. Borazine, sind ein fester Bestandteil der organischen, biomedizinischen und Materialchemie. Überraschenderweise sind Heterocyclen, die P und Al enthalten, selten. Wir haben nun Phosphaalumene in Reaktionen mit Alkinen, Alkenen und konjugierten Doppelbindungssystemen eingesetzt. Mit sterisch anspruchsvollen Alkinen wurden 1,2‐Phosphaalumete erhalten, während die Reaktion mit HCCH oder HCCSiMe3 1,4‐Phosphaaluminabarrelene ergab. Mit Styrol wurden gesättigte 1,2‐Phosphaalumate gebildet, die mit weiteren Äquivalenten Styrol zu verschiedenen Regio‐Isomeren von 1,4‐Aluminaphosphorinanen weiterreagierten. Mit Ethylen wird ebenfalls ein 1,4‐Aluminaphosphorinan erhalten, während mit 1,3‐Butadien ein bicyclisches System mit einer Aluminacyclopentan‐ und einer Phosphiran‐Einheit synthetisiert wurde. Die experimentellen Arbeiten werden durch theoretische Studien unterstützt, um den Mechanismus der Bildung dieser Heterocyclen genauer zu untersuchen. [ABSTRACT FROM AUTHOR]

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.)

Boron nitride (BN) ceramics are promising candidates for high-temperature structural and functional materials. However, it is difficult to sinter dense additive-free bulk BN monoliths because of the covalent bond and flake structure. Here, we report dense bulk BN with relative density higher than 95% without sintering additives achieved via a self-densifying approach of borazine within a wide temperature range from 800 °C to 1800 °C. A polyborazylene with a controlled degree of cross-linking was synthesized and press-molded into shaped green bodies, which were pressureless pyrolyzed into porous frameworks and then densified through repeated borazine infiltration and pyrolysis method. The microstructural and crystalline evolution of the bulk BN ceramics, as well as the corresponded mechanical, thermal and dielectric properties were investigated. • Dense additive-free bulk BN ceramics with >95% relative density were prepared from 800 °C to 1800 °C. • The crystalline process from amorphous phase to turbostratic and h-BN phases were revealed. • The mechanical, thermal and dielectric properties of the dense bulk BN ceramics were obtained. [ABSTRACT FROM AUTHOR]

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]

In this project, hexagonal‑boron nitride nanosheets synthesized on aluminum substrates using the atmospheric pressure micro plasma (APMP) technique with borazine as the precursor. The synthesized nanosheets were subjected to comprehensive characterization techniques to evaluate their properties and potential applications. To confirm the formation of the hexagonal phase of boron nitride, X-ray diffractometry was employed. Scanning electron microscopy was utilized to investigate the microstructure, nanoparticle size estimation, average roughness and pore size. Energy-dispersive X-ray analysis (EDX) was implied to assess the elemental composition of the nanosheets. Further insights into the surface chemistry of these nanosheets were obtained through Fourier-transform infrared (FT-IR) spectroscopy. The optical properties of the nanosheets, particularly their reflectivity in the UV-VIS range of the electromagnetic spectrum, were characterized using UV-VIS spectroscopy. Additionally, Vickers hardness tests were conducted to assess the hardness of the nanosheets. The results of this study demonstrate that the hexagonal‑boron nitride nanosheets form a uniform and continuous coating on Al. Importantly, these nanosheets exhibit minimal interference with the reflectivity of Al in the UV-VIS spectral region. This finding suggests that hexagonal‑boron nitride nanosheets have promising potential as coatings for various aluminum-based applications, including optical mirrors, solar energy concentrators, fuselage materials, bearings, and coinage. [Display omitted] [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]

This study uses first-principles calculations to investigate and compare the hydrogen storage properties of Ti doped benzene (C 6 H 6 Ti) and Ti doped borazine (B 3 N 3 H 6 Ti) complexes. C 6 H 6 Ti and B 3 N 3 H 6 Ti complex each can adsorb four H 2 molecules, but the former has a 0.11 wt% higher H 2 uptake capacity than the latter. Ti atoms bind to C 6 H 6 more strongly than B 3 N 3 H 6. The hydrogen adsorption energies with Gibbs free energy correction for C 6 H 6 Ti and B 3 N 3 H 6 Ti complexes are 0.17 and 0.45 eV, respectively, indicating reversible hydrogen adsorption. The hydrogen adsorption properties of C 6 H 6 Ti have also been studied after boron (B) and nitrogen (N) atom substitutions. Several B and N substituted structures between C 6 H 6 Ti and B 3 N 3 H 6 Ti with different boron and nitrogen concentration and at different positions were considered. Initially, one boron and one nitrogen atom is substituted for two carbon atoms of benzene at three different positions and three different structures are obtained. Seven structures are possible when four carbon atoms of benzene are replaced by two boron and two nitrogen atoms at different positions. The hydrogen storage capacity of the C 6 H 6 Ti complex increases as boron and nitrogen atom concentrations increases. The positions of substituted boron and nitrogen atoms have less impact on H 2 uptake capacity for the same B and N concentration. The position and concentration of B and N affects the H 2 adsorption energy as well as the temperature and pressure range for thermodynamically favorable H 2 adsorption. The H 2 desorption temperature for all the complexes is found to be higher than 250 K indicates the stronger binding of H 2 molecules with these complexes. • Ti decorated heterocyclic (BCN) rings have higher H 2 uptake capacity than Benzene-Ti and Borazine-Ti complexes. • The H 2 uptake capacity of Benzene-Ti complex increases with an increasing concentrations of boron and nitrogen atoms. • H 2 adsorption is thermodynamically more favourable on Borazine-Ti complex than the Benzene-Ti complex. • H 2 molecules interact more strongly with Borazine-Ti complex than other Ti decorated heterocyclic rings. [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.

[Display omitted] • Structure, stability and bonding character of the NgBz (Ng = He-Xe; Bz = B 3 N 3 H 6). • The NgBz are describable as complexes of Ng ligated to one, two, or three N atoms. • The stability of the NgBz increases in the order N-mono < N-di < N-three. • The stability of the NgBz is determined mainly by the dispersive interaction. • The NgBz are compared with other investigated complexes of Ng with larger BN sheets. The complexes of He, Ne, Ar, Kr and Xe with B 3 N 3 H 6 were investigated by MP2, CCSD(T), and SAPT ab initio methods, and accurate procedures of bonding analysis. These systems are describable as mono-, di-, and tri-coordinated to the N atoms, their stabilities following the order N-mono < N-di < N-tri. The binding energies are within 1 or 2 kcal mol−1, and the interactions are dominated by the dispersion. The results are compared with those obtained recently from a DFT study on the complexes of He, Ne, Ar, and Kr with larger BN sheets [Phys. Chem. Chem. Phys. 24 (2022) 2554–2566.]. [ABSTRACT FROM AUTHOR]

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]

Borazine rings act as a pivotal part in siliconboroncarbonitride ceramics (SiBCN) for high-temperature stability and great resistance to crystallization. A detailed investigation of the ring formation mechanism will guide the design and synthesis of SiBCN to meet application requirements under extreme conditions. Boron trichloride (BCl 3) and hexamethyldisilazane (HN(SiMe 3) 2) are common raw materials for the synthesis of precursors for SiBCN. In this paper, quantum chemical calculation was used to study the cyclization reaction mechanism between BCl 3 and HN(SiMe 3) 2 to form trichloroborazine (TCBZ) at the MP2/6-31G (d,p) level of theory. We discussed the structure properties, reaction pathways, energy barriers, reaction rates, and other aspects in detail. The results show that BCl 3 and HN(SiMe 3) 2 alternately participate in the reaction process, accompanied by the release of trimethylchlorosilane (TMCS), and that the entire reaction shows an absolute advantage in terms of energy. In the Step by step reaction, lower reaction barriers are formed due to the introduction of BCl 3 with more heat released compared to that for the introduction of HN(SiMe 3) 2. The final single-molecule cyclization and TMCS elimination steps are found to be faster compared to all previous bimolecular reactions. [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]

Which potential energy curve is correct? [Display omitted] • The most unexpected findings is that potential energy curves of HXeF⋅⋅⋅M 3 N 3 H 6 (M = B, Ga) with respect to the H 2 -H 1 -F-Xe dihedral angle depend on the density functional theories and the second order perturbation theory. • Thus, how to produce correctly these potential energy curves become a serious challenge for theoretical models. Theoretical studies on the weak interactions in HXeF⋅⋅⋅M 3 N 3 H 5 Y (M = B, Al and Ga; Y = H, F, Cl, Br, CF 3 , NH 2 and CH 3) have been carried out with B3LYP-D3(BJ)/aug-cc-pVTZ (aug-cc-pVTZ-PP for Xe). Electron-withdrawing groups make HXeF⋅⋅⋅M 3 N 3 H 5 Y more stable than electron-donating groups. AIM analysis indicates N-H⋅⋅⋅F interaction plays a dominant role in the stabilities of the studied complexes. It is found that potential energy curves of HXeF⋅⋅⋅M 3 N 3 H 6 (M = B, Ga) with respect to the H 2 -H 1 -F-Xe dihedral angle depend on the computational methods. Thus, how to produce correctly these potential energy curves becomes a serious challenge for the accuracy of theoretical models. [ABSTRACT FROM AUTHOR]

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.

Abstract Use of metal functionalized molecules for reversible hydrogen storage is well established due to their high gravimetric hydrogen storage capacity. We study BN-analogue of [2,2]paracyclophane (BNP22) containing two borazine rings and functionalized with Sc and Ti atoms to interpret its hydrogen binding capacity. First principles calculations based on density functional theory suggest that BNP22-2Sc and BNP22 2Ti systems can have a gravimetric density as high as 8.9 and 9.9 % , respectively. The BNP22-2Sc system can be operated under ambient thermodynamic conditions within the allowable pressure range of 3–30 atm and van 't Hoff desorption temperature range of 219–438 K as confirmed from molecular dynamics and occupation number studies. Both the systems establish Brønsted-Evans-Polanyi relation with BNP22-2Sc having significantly less activation energy of 0.38 eV. We discuss the energetic stability of these systems with respect to vibrational frequency, absolute hardness, and transition states. Consistent with 2020 targets set by the DOE, BNP22-2Sc proves to be budding hydrogen storage material. Graphical abstract Image 1 Highlights • H 2 storage in BN-analogue of paracyclophane functionalized with metals is studied. • On saturation, Sc and Ti adsorbs maximum of 8 and 10H 2 molecules, respectively. • H 2 adsorbs the metals by Kubas interaction. • Both Sc and Ti functionalized BNP22 follow Brønsted-Evans-Polanyi relation. • Hydrogen storage capacity is found to be above 8.9 wt %. [ABSTRACT FROM AUTHOR]

Abstract Covalent organic frameworks (COFs), metal organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) have been widely studied in gas separation applications due to their large surface areas, high pore volumes, tunable pore sizes and chemical stabilities. In this study, separation performances of 153 COFs, 14 IRMOFs and 8 ZIFs were assessed for efficient removal of carbon tetrachloride (CCl 4) from CCl 4 /Ar, CCl 4 /N 2 , CCl 4 /O 2 mixtures at 298 K and infinite dilution. The top performing three materials in each group, namely, borazine-linked polymer (BLP-2H-AA), IRMOF-11 and ZIF-6 were identified. Single-component, binary mixture and quaternary mixture adsorption isotherms of argon (Ar), CCl 4 , nitrogen (N 2) and oxygen (O 2) in these materials were computed at 298 K and various total pressures from 10−3 to 1.5 × 104 kPa. Mixture adsorption selectivities and separation potentials were then calculated and the effect of relative humidity on the performance of adsorption-based CCl 4 separation was examined. Single-component and quaternary mixture diffusion coefficients of Ar, CCl 4 , N 2 and O 2 were finally computed. Our results showed that ZIF-6 exhibits the highest adsorption selectivity and the highest separation potential for CCl 4 /Ar, CCl 4 /N 2 and CCl 4 /O 2 mixtures, followed by IRMOF-11 and BLP-2H-AA. Results of this computational study will be highly useful to identify the promising materials for removal of CCl 4 from air. Graphical abstract Image 1 Highlights • COFs, IRMOFs and ZIFs were computationally studied for removal of CCl 4 from air. • The adsorption equilibria for binary and quaternary gas mixtures were discussed. • Structure-performance relationships were discussed for CCl 4 adsorption. • Single-component and mixture gas diffusivities were computed using MD simulations. • High adsorption selectivity of ZIF-6 was achieved. [ABSTRACT FROM AUTHOR]

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]

Graphical abstract Highlights • Benzoxazine-substituted borazine coatings were applied on aluminum and thermally cured. • Obtained microstructures show two phases, coarsening with the borazine concentration. • The borazine derivative increases the hydrophobicity of the generated composite. • Corrosion properties of the composites are strongly related to the microstructure. • For the lowest concentration (0.5 wt% borazine) a durable corrosion barrier is obtained. Abstract In this paper, laboratory synthesized Phenol-paraPhenyleneDiAmine (P-pPDA) benzoxazine containing different amounts of B-trimesityl-N-triphenylborazine was applied by spin coating on aluminum and thermally cured. The addition of the borazine derivative (borazine 1) does not appear to modify the curing characteristics of the P-pPDA matrix itself as shown by FTIR, DSC and DEA analyses; however, some interactions - chemical and/or physical (co-crystallization) – between P-pPDA and borazine 1 cannot be excluded. The microstructure of the composites is characterized by a two phase system consisting of a dispersion of nanosized (10–20 nm) clusters for the lowest borazine 1 concentration (0.5 wt%), evolving towards bigger (100–200 nm), agglomerated clusters for higher borazine 1 concentrations (3 wt%) and finally, continuous, dendritic structures within the P-pPDA matrix for the highest borazine 1 concentration (10 wt%). The benzoxazine composite coating containing 0.5 wt% trimesitylborazine derivative showed a largely increased and durable ability to protect the aluminum substrate. It is shown that a highly capacitive behavior and durable barrier properties can be obtained for P-pPDA coatings containing such a low amount of borazine derivative homogeneously dispersed in the benzoxazine matrix. For concentrations of 3 wt%, as agglomeration took place and dendrites appeared for the highest concentration of borazine derivative (10 wt%), the corrosion resistance decreased with time. [ABSTRACT FROM AUTHOR]