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1. Intra- and intermolecular C—H...F hydrogen bonds in the crystal structure of 1,2-bis[2-(2,3,4,5-tetrafluorophenyl)ethynyl]benzene

   https://doi.org/10.1107/S2056989024010995  

   Bosch, Eric; Bowling, Nathan P (December 2024, Acta Crystallographica Section E Crystallographic Communications)

   The title molecule, C₂₂H₆F₈, crystallizes in the monoclinic space groupP2₁/cwith two unique molecules in the asymmetric unit andZ= 8. Each molecule features a short intramolecularsp²-C—H...F hydrogen bond with H...F separations at 2.363 (14) and 2.270 (14) Å, corresponding to 91 and 87.5% of the sum of the van der Waals radii, and C—H...F angles of 158.3 (14) and 166.8 (14)°, respectively. Each molecule also forms an intermolecular bifurcated CH...(F)₂interaction with H...F distances ranging from 2.500 (16) to 2.597 (17) Å. 

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2. Molecular Turnstiles Featuring Bicyclic Rotators: Solution and Solid‐State Investigation of Steric and Electronic Concerns

   https://doi.org/10.1002/ejoc.202300716  

   Rammer, Megan_L; Gonnering, Emily_R; Driscoll, Zakarias_L; Vang, Herh_G; Bosch, Eric; Bowling, Nathan_P (August 2023, European Journal of Organic Chemistry)

   Abstract A molecular rotor is created when a 2,1,3‐benzothiadiazole rotator is incorporated into a rigid arylene ethynylene framework supported by pyridine coordination to a metal (Ag⁺or PdCl₂) guest. Comparisons to a similarly sized naphthyl rotator via¹H NMR spectroscopy provide insights into the movement of these bicyclic rotators relative to the rigid stator framework. Chemical shift increases of 0.3 ppm, or more, upon metal complexation are consistent with through‐space interaction of the central arene with a bound PdCl₂guest. Further study via X‐ray crystallography illustrates that rotation of the 2,1,3‐benzothiadiazole unit in the solid state is likely hampered by relatively strong chalcogen bonding (N⋅⋅⋅S distance of 2.93 Å), forming 2S‐2N squares between benzothiadiazoles of neighboring complexes. Strong π–π interactions (3.29–3.36 Å) between neighboring complexes likewise restrict solid‐state rotation of the potential benzothiadiazole rotator. Modest changes to UV–vis spectra upon metal coordination suggest that electronic properties are mostly independent of stator configuration. 

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3. Cyclotetrabenzoin Acetate: A Macrocyclic Porous Molecular Crystal for CO ₂ Separations by Pressure Swing Adsorption**

   https://doi.org/10.1002/anie.202102813  

   Wang, Yao‐Ting; McHale, Corie; Wang, Xiqu; Chang, Chung‐Kai; Chuang, Yu‐Chun; Kaveevivitchai, Watchareeya; Miljanić, Ognjen Š.; Chen, Teng‐Hao (May 2021, Angewandte Chemie International Edition)

   Abstract A porous molecular crystal (PMC) assembled by macrocyclic cyclotetrabenzoin acetate is an efficient adsorbent for CO₂separations. The 7.1×7.1 Å square pore of PMC and its ester C=O groups play important roles in improving its affinity for CO₂molecules. The benzene walls of macrocycle engage in an apparent [π⋅⋅⋅π] interaction with the molecule of CO₂at low pressure. In addition, the polar carbonyl groups pointing inward the square channels reduce the size of aperture to a 5.0×5.0 Å square, which offers kinetic selectivity for CO₂capture. The PMC features water tolerance and high structural stability under vacuum and various gas adsorption conditions, which are rare among intrinsically porous organic molecules. Most importantly, the moderate adsorbate‐adsorbent interaction allows the PMC to be readily regenerated, and therefore applied to pressure swing adsorption processes. The eluted N₂and CH₄are obtained with over 99.9 % and 99.8 % purity, respectively, and the separation performance is stable for 30 cycles. Coupled with its easy synthesis, cyclotetrabenzoin acetate is a promising adsorbent for CO₂separations from flue and natural gases. 

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4. A charged diatomic triple-bonded U≡N species trapped in C82 fullerene cages

   https://doi.org/10.1038/s41467-022-34651-5  

   Meng, Qingyu; Abella, Laura; Yao, Yang-Rong; Sergentu, Dumitru-Claudiu; Yang, Wei; Liu, Xinye; Zhuang, Jiaxin; Echegoyen, Luis; Autschbach, Jochen; Chen, Ning (December 2022, Nature Communications)

   Abstract Actinide diatomic molecules are ideal models to study elusive actinide multiple bonds, but most of these diatomic molecules have so far only been studied in solid inert gas matrices. Herein, we report a charged U≡N diatomic species captured in fullerene cages and stabilized by the U-fullerene coordination interaction. Two diatomic clusterfullerenes, viz. UN@C_s(6)-C₈₂and UN@C₂(5)-C₈₂, were successfully synthesized and characterized. Crystallographic analysis reveals U-N bond lengths of 1.760(7) and 1.760(20) Å in UN@C_s(6)-C₈₂and UN@C₂(5)-C₈₂. Moreover, U≡N was found to be immobilized and coordinated to the fullerene cages at 100 K but it rotates inside the cage at 273 K. Quantum-chemical calculations show a (UN)²⁺@(C₈₂)²⁻electronic structure with formal +5 oxidation state (f¹) of U and unambiguously demonstrate the presence of a U≡N bond in the clusterfullerenes. This study constitutes an approach to stabilize fundamentally important actinide multiply bonded species. 

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5. Spectral Contamination of the 6300 Å Emission in Single‐Etalon Fabry‐Perot Interferometers

   https://doi.org/10.1029/2023JA031601  

   Kerr, R. B.; Kapali, S.; Harding, B. J.; Riccobono, J.; Migliozzi, M. A.; Souza, J. R.; Mesquita, R.; Dandenault, P.; Wu, Q.; Pimenta, A. A.; et al (September 2023, Journal of Geophysical Research: Space Physics)

   Abstract The spectral line profile of the atomic oxygen O¹D₂—³P₂transition near 6300 Å in the airglow has been used for more than 50 years to extract neutral wind and temperature information from the F‐region ionosphere. A new spectral model and recent samples of this airglow emission in the presence of the nearby lambda‐doubled OH Meinel (9‐3) P₂(2.5) emission lines underscores earlier cautions that OH can significantly distort the OI line center position and line width observed using a single‐etalon Fabry‐Perot interferometer (FPI). The consequence of these profile distortions in terms of the emission profile line width and Doppler position is a strong function of the selected etalon plate spacing. Single‐etalon Fabry‐Perot interferometers placed in the field for thermospheric measurements have widely varying etalon spacings, so that systematic wind biases caused by the OH line positions differ between instruments, complicating comparisons between sites. Based on the best current determinations of the OH and O¹D line positions, the ideal gap for a single‐etalon FPI wind measurements places the OH emissions in the wings of the O¹D spectral line profile. Optical systems that can accommodate prefilters with square passbands less than ∼3 Å in the optical beam can effectively block the OH contamination. When that is not possible, a method to fit for OH contamination and remove it in the spectral background of an active Fabry‐Perot system is evaluated. 

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