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1. Structural insights into supramolecular interactions in isostructural salts of 2,4,6-triaminopyrimidinium with various heterocyclic carboxylates

   https://doi.org/10.1107/S2053229624008787  

   Mohana, Marimuthu; Gomathi, Sundaramoorthy; Thomas_Muthiah, Packianathan; Butcher, Ray J (November 2024, Acta Crystallographica Section C Structural Chemistry)

   2,4,6-Triaminopyrimidine is an interesting and challenging molecule due to the presence of multiple hydrogen-bond donors and acceptors. Its noncovalent interactions with a variety of carboxylic acids provide several supramolecular aggregates with frequently occurring molecular synthons. The present work focuses on the supramolecular interactions of 2,4,6-triaminopyrimidinium 3-(indol-3-yl)propionate–3-(indol-3-yl)propionic acid (1/1), C₄H₈N₅⁺·C₁₁H₁₀NO₂⁻·C₁₁H₁₁NO₂, (I), 2,4,6-triaminopyrimidinium 2-(indol-3-yl)acetate, C₄H₈N₅⁺·C₁₀H₈NO₂⁻, (II), 2,4,6-triaminopyrimidinium 5-bromothiophene-2-carboxylate, C₄H₈N₅⁺·C₅H₂BrO₂S⁻, (III), and 2,4,6-triaminopyrimidinium 5-chlorothiophene-2-carboxylate, C₄H₈N₅⁺·C₅H₂ClO₂S⁻, (IV). All four salts exhibit robust homomeric and heteromericR₂²(8) ring motifs. Salts (I) and (II) develop sextuple [in (I)] and quadruple [in (I) and (II)] hydrogen-bonded arrays through fused-ring motifs. Salt (II) exhibits a rosette-like architecture. Salt (IV) is isostructural and isomorphous with salt (III), exhibiting an identical crystal structure with a different composition and an identical supramolecular architecture. In salts (III) and (IV), a linear hetero-tetrameric motif is formed and, in addition, both salts exhibit halogen–π interactions which enhance the crystal stability. All four salts develop a supramolecular hydrogen-bonded pattern facilitated by several N—H...O and N—H...N hydrogen bonds with multiple furcated donors and acceptors. 

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2. Tailorable Multi‐Modular Pore‐Space‐Partitioned Vanadium Metal‐Organic Frameworks for Gas Separation

   https://doi.org/10.1002/adma.202403834  

   Wang, Wei; Chen, Yichong; Feng, Pingyun; Bu, Xianhui (July 2024, Advanced Materials)

   Abstract Currently, few porous vanadium metal‐organic frameworks (V‐MOFs) are known and even fewer are obtainable as single crystals, resulting in limited information on their structures and properties. Here this work demonstrates remarkable promise of V‐MOFs by presenting an extensible family of V‐MOFs with tailorable pore geometry and properties. The synthesis leverages inter‐modular synergy on a tri‐modular pore‐partitioned platform. New V‐MOFs show a broad range of structural features and sorption properties suitable for gas storage and separation applications for C₂H₂/CO₂, C₂H₆/C₂H₄, and C₃H₈/C₃H₆. Thec/aratio of the hexagonal cell, a measure of pore shape, is tunable from 0.612 to 1.258. Other tunable properties include pore size from 5.0 to 10.9 Å and surface area from 820 to 2964 m²g⁻¹. With C₂H₂/CO₂selectivity from 3.3 to 11 and high uptake capacity for C₂H₂from 65.2 to 182 cm³g⁻¹(298K, 1 bar), an efficient separation is confirmed by breakthrough experiments. The near‐record high uptake for C₂H₆(166.8 cm³g⁻¹) contributes to the promise for C₂H₆‐selective separation of C₂H₆/C₂H₄. The multi‐module pore expansion enables transition from C₃H₆‐selective to more desirable C₃H₈‐selective separation with extraordinarily high C₃H₈uptake (254.9 cm³g⁻¹) and high separation potential (1.25 mmol g⁻¹) for C₃H₈/C₃H₆(50:50 v/v) mixture. 

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3. Physical and Chemical Properties of Galactic Molecular Gas toward QSO J1851+0035

   https://doi.org/10.3847/1538-4357/ad3d5b  

   Narita, Kanako; Sakamoto, Seiichi; Koda, Jin; Yoshimura, Yuki; Kohno, Kotaro (July 2024, The Astrophysical Journal)

   Abstract Atacama Large Millimeter/submillimeter Array (ALMA) data toward QSO J1851+0035 (l= 33.°498,b= +0.°194) were used to study absorption lines by Galactic molecular gas. We detected 17 species (CO,¹³CO, C¹⁸O, HCO⁺, H¹³CO⁺, HCO, H₂CO, C₂H,c-C₃H,c-C₃H₂, CN, HCN, HNC, CS, SO, SiO, and C) and set upper limits to 18 species as reference values for chemical models. About 20 independent velocity components at 4.7–10.9 kpc from the Galactic center were identified. Their column density and excitation temperature estimated from the absorption study, as well as the CO intensity distributions obtained from the FUGIN survey, indicate that the components withτ≲1 correspond to diffuse clouds or cloud outer edges. Simultaneous multiple-Gaussian fitting of COJ= 1–0 andJ= 2–1 absorption lines shows that these are composed of narrow- and broad-line components. The kinetic temperature empirically expected from the high HCN/HNC isomer ratio (≳4) reaches ≳40 K and the corresponding thermal width accounts for the line widths of the narrow-line components. CN-bearing molecules and hydrocarbons have tight and linear correlations within the groups. The CO/HCO⁺abundance ratio showed a dispersion as large as 3 orders of magnitude with a smaller ratio in a smallerN(HCO⁺) (or lowerA_V) range. Some of the velocity components are detected in single-dish CO emission and ALMA HCO⁺absorption but without corresponding ALMA CO absorption. This may be explained by the mixture of clumpy CO emitters not resolved with the ∼1 pc single-dish beam surrounded by extended components with a very low CO/HCO⁺abundance ratio (i.e., CO-poor gas). 

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4. Initial-site characterization of hydrogen migration following strong-field double-ionization of ethanol

   https://doi.org/10.1038/s41467-023-44311-x  

   Severt, Travis; Weckwerth, Eleanor; Kaderiya, Balram; Feizollah, Peyman; Jochim, Bethany; Borne, Kurtis; Ziaee, Farzaneh; P, Kanaka Raju; Carnes, Kevin D; Dantus, Marcos; et al (December 2024, Nature Communications)

   Abstract An essential problem in photochemistry is understanding the coupling of electronic and nuclear dynamics in molecules, which manifests in processes such as hydrogen migration. Measurements of hydrogen migration in molecules that have more than two equivalent hydrogen sites, however, produce data that is difficult to compare with calculations because the initial hydrogen site is unknown. We demonstrate that coincidence ion-imaging measurements of a few deuterium-tagged isotopologues of ethanol can determine the contribution of each initial-site composition to hydrogen-rich fragments following strong-field double ionization. These site-specific probabilities produce benchmarks for calculations and answer outstanding questions about photofragmentation of ethanol dications; e.g., establishing that the central two hydrogen atoms are 15 times more likely to abstract the hydroxyl proton than a methyl-group proton to form H$${}_{3}^{+}$$ ${}_3^{+}$and that hydrogen scrambling, involving the exchange of hydrogen between different sites, is important in H₂O⁺formation. The technique extends to dynamic variables and could, in principle, be applied to larger non-cyclic hydrocarbons. 

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5. 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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