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Benzoborirene carrying a bulky Trip2C6H3 (Trip = 2,4,6-tri-iso-Pr3C6H2) group at boron reacts with the dienophile 4-phenyl-1,2,4-triazoline-3,5-dione and the diene 3,6-di(4-pyridyl)-1,2,4,5-tetrazine by opening of the borirene ring rather than undergoing the typical Diels–Alder reactions. The formal insertion results in diazaborole and azaborolo[1,5-b][1,2,4,5]tetrazine derivatives, respectively. [ABSTRACT FROM AUTHOR]

Cycloreversion of diheptacenes, the covalently bound dimers of heptacene, in the solid state produces heptacene. In addition, diheptacendiyl diradical can be detected by ESR spectroscopy. The diradical has a small singlet–triplet energy gap of −0.02 kJ mol−1 (−4.8 × 10−3 kcal mol−1) in favor of the singlet state and is persistent in solid heptacene. [ABSTRACT FROM AUTHOR]

1,2‐Azaborinines are the BN analogues of arynes through exchange of the formal CC triple bond by an isoelectronic BN bond. The BN‐arynes are an underexplored class of reactive intermediates. Dibenzo[c,e][1,2]azaborinine (10,9‐BN‐phenanthryne) 1 was inferred as reactive intermediate by trapping reactions. Here it is shown that 1 can be generated in the gas phase by thermolysis from the pyridine adduct of 9‐azido‐9‐borafluorene by cleavage of the dative bond with pyridine and dinitrogen extrusion. The ionization potential of 1 is 8.2 eV with ionization resulting from the π HOMO. Under cryogenic matrix isolation conditions, 9‐azido‐9‐borafluorene photolysis results in isomerization to the dinitrogen adduct of 1 without involvement of a triplet borylnitrene intermediate. Photochemical nitrogen extrusion from 1 ⋅ N2 is not possible and nitrogen fixation is irreversible under cryogenic conditions. In contrast, 2,4,7,9‐tetra‐tert‐butyldibenzo[c,e][1,2]azaborinine can be photogenerated from the corresponding azidoborole precursor under cryogenic matrix isolation conditions, and nitrogen fixation is precluded due to steric hindrance. The BN stretching vibration at about 1750 cm−1 is much weaker than in typical linear diaryl iminoboranes. [ABSTRACT FROM AUTHOR]

Preliminary computations of NBN-benzo[f,g]tetracene/BINOL tethered structures (R)-/(S)-1 and (R)-/(S)-2 that suggest high oscillator strengths f and dissymmetry factors for CPL glum incited us to synthesize these compounds. The optical transitions within these structures have strong charge-transfer character from the benzotetracene-localized HOMOs to the LUMOs located at the BINOL. Large Stokes shifts of around 3500 cm−1 are observed alongside quantum yields of 53–64%. The absorption and luminescence dissymmetry factors from ECD and CPL spectra were measured as gabs = ±0.7 × 10−3 (1) and ±1.0 × 10−3 (2), and glum = ±0.5–0.6 × 10−3 (1) and ±1.6 × 10−3 (2), resulting in a CPL brightness (BCPL) of 12.7–15.1 M−1 cm−1. This work shows that computational screening of chiroptical properties prior to synthesis is useful for identification of suitable materials. [ABSTRACT FROM AUTHOR]

The 2π electron 1,3‐dipole boradigermaallyl, valence‐isoelectronic to an allyl cation, is synthesized from a bis(germylene). It reacts with benzene at room temperature by insertion of a boron atom into the benzene ring. Computational investigation of the mechanism shows the boradigermaallyl reacting with a benzene molecule in a concerted (4+3) or [π4s+π2s] cycloaddition reaction. Thus, the boradigermaallyl acts as a highly reactive dienophile in this cycloaddition reaction with nonactivated benzene as diene unit. This type of reactivity provides a novel platform for ligand assisted borylene insertion chemistry. [ABSTRACT FROM AUTHOR]

Context. The absorption bands of the interstellar medium (ISM) in the optical and near-infrared regions called the diffuse interstellar bands (DIBs) have been known for almost a century, yet their origins remain largely unknown. Knowledge of molecular carriers of DIBs would allow for a much better understanding of the chemistry and physics of the ISM. Polycyclic aromatic hydrocarbons (PAHs) and, among them, polyacenes have been suggested as promising candidates for carriers of DIBs. Aims. In this paper, we report on the spectroscopy of heptacene (Hep), the polyacene molecule consisting of seven aromatic rings in a linear arrangement, in its cationic and anionic forms (Hep+/-). The performed spectroscopic studies made it possible to accurately determine the Hep+/- absorption band positions and to conduct a direct comparison of laboratory and observational spectra. Methods. We utilized helium-tagging action spectroscopy to measure the spectra of Hep+/- in a wide spectral range of 3000-13 000 Å. In most cases, the spectra obtained by this method can be directly compared with the observational spectra. By analyzing the spectral shift as a function of the number of attached helium atoms, we obtained precise estimates of the gas-phase band positions. Quantumchemical computations were used to support and interpret the findings. Matrix isolation spectroscopy provided information on the spectral properties of neutral Hep and extended the spectral range for Hep+. Results. We found several absorption bands characterized by a rather large full width at half maximum in the spectra of Hep+/-. The two most intense bands were found at 4714 ± 5Å and 12 250 ± 12Å for Hep+ and at 4673 ± 14Å and 11326 ± 4Å for Hep-. We did not find any good match between laboratory and observational spectra. In particular, the intrinsic width of the absorption bands of Hep+/- is much higher than that of most observed DIBs. Conclusions. The non-detection of Hep+/- in the observational spectra excludes the bottom-up formation route for polyacenes in the ISM. Larger polyacene molecules could still be considered as potential carriers of DIBs in the case of an efficient top-down formation route. All currently measured polyacene ions exhibit relatively broad absorption bands. Therefore, additional spectroscopy studies of neutral polyacenes and larger polyacene ions as well as the study of possible top-down formation routes are suggested. [ABSTRACT FROM AUTHOR]

The article titled "Inside Cover: Facile Energy Release from Substituted Dewar Isomers of 1,2‐Dihydro‐1,2‐Azaborinines Catalyzed by Coinage Metal Lewis Acids" discusses the use of coinage metals as catalysts for energy release from a specific molecule called 1,2‐dihydroazaborinine. This molecule is a potential candidate for molecular solar thermal storage systems. The researchers, Holger F. Bettinger, Ivana Fleischer, and their team, conducted mechanistic studies and computational analysis to gain insights into the catalytic system. The article also presents the first crystal structure of the energy-rich Dewar dihydroazaborinine isomer coordinated to Ag(I). [Extracted from the article]

The article titled "Facile Energy Release from Substituted Dewar Isomers of 1,2-Dihydro-1,2-Azaborinines Catalyzed by Coinage Metal Lewis Acids" published in Angewandte Chemie discusses the use of coinage metals as catalysts for energy release from the Dewar isomer of 1,2-dihydroazaborinine. This is a promising molecular solar thermal storage system. The researchers, Holger F. Bettinger, Ivana Fleischer, and their team, conducted mechanistic studies and computational analysis to gain insights into the catalytic system. They also presented the first crystal structure of the energy-rich Dewar dihydroazaborinine isomer coordinated to Ag(I). [Extracted from the article]