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1. Syntheses and crystal structures of three triphenylsulfonium salts of manganese(II), iron(III) and cobalt(II)

   https://doi.org/10.1107/S2056989025006668  

   Callaway, Waylan; Elterman, Matthew; Krasilnikov, Nikita; Roberts, Gavin; Rutan, Davis; Spencer, Ty; Padgett, Clifford W; Lynch, Will E (August 2025, Acta Crystallographica Section E Crystallographic Communications)

   Bis(triphenylsulfonium) tetrachloridomanganate(II), (C₁₈H₁₅S)₂[MnCl₄] (I), triphenylsulfonium tetrachloridoferrate(III), (C₁₈H₁₅S)[FeCl₄] (II), and bis(triphenylsulfonium) tetrachloridocobaltate(II), (C₁₈H₁₅S)₂[CoCl₄] (III), crystallize in the monoclinic space groupsP2₁/n[(I) and (III)] andP2₁/c[(II)]. Compounds (I) and (III) each contain two crystallographically independent triphenylsulfonium (TPS⁺) cations in the asymmetric unit, whereas (II) has one. In all three compounds, the sulfonium centers adopt distorted trigonal–pyramidal geometries, with S—C bond lengths falling roughly in the 1.78–1.79 Å range and C—S—C angles observed at about 101 to 106°. The [MCl₄]ⁿ⁻anions (M= Mn²⁺, Fe³⁺, Co²⁺;n= 2,1,2) adopt slightly distorted tetrahedral geometries, withM—Cl bond lengths in the 2.19–2.38 Å range and Cl—M—Cl angles of approximately 104–113°. Hirshfeld surface analyses shows that H...H and H...C contacts dominate the TPS⁺cation environments, whereas H...Cl and shortM—S interactions link each [MCl₄]ⁿ⁻anion to the surrounding cations. In (I) and (III), inversion-centered π–π stacking further consolidates the crystal packing, while in (II) no π–π interactions are observed. 

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2. Crystal structures of three salts of the triphenylsulfonium ion

   https://doi.org/10.1107/S2056989025000118  

   Artis, Rylan; Callaway, Waylan; Heyward, Elizabeth; Reyes, Naomi; Roberts, Gavin; Van_Ostenbridge, Kaitlyn; Padgett, Clifford W; Lynch, Will E (February 2025, Acta Crystallographica Section E Crystallographic Communications)

   The reactions of triphenylsulfonium chloride ([TPS][Cl]) with various acids in methanol yield the corresponding salts triphenylsulfonium triiodide, C₁₈H₁₅S⁺·I₃⁻or [TPS][I₃] (I), triphenylsulfonium perchlorate, C₁₈H₁₅S⁺·ClO₄⁻or [TPS][ClO₄] (II), and triphenylsulfonium hexafluorophosphate, C₁₈H₁₅S⁺·PF₆⁻or [TPS][PF₆] (III), as crystalline products. These crystals were structurally characterized by single-crystal X-ray diffraction. In all three compounds, the sulfur atom in the triphenylsulfonium cation adopts a distorted trigonal–pyramidal geometry. [TPS][I₃] (I) and [TPS][PF₆](III) both crystallize in the space groupP2₁/n, while [TPS][ClO₄] (II) crystallizes inP2₁. The S—C bond lengths are comparable across the three salts, and the S—C—S bond angles are consistently between 102 and 106°. Hirshfeld surface analyses reveal that each structure is dominated by hydrogen-based intermolecular contacts, supplemented by anion-specific interactions such as I...H in (I), O...H in (II), and F...H in (III). These contacts organize the ions into mono-periodic ribbon- or chain-like arrangements. No significant π–π stacking is observed. 

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3. Generalized T _e ([O iii ])– T _e (He i ) Discrepancies in Ionized Nebulae: Possible Evidence of Case B Deviations and Temperature Inhomogeneities

   https://doi.org/10.3847/1538-4357/adc67a  

   Méndez-Delgado, J E; Skillman, E D; Aver, E; Morisset, C; Esteban, C; García-Rojas, J; Kreckel, K; Rogers, N_S J; Rosales-Ortega, F F; Arellano-Córdova, K Z; et al (June 2025, The Astrophysical Journal)

   Abstract The physics of recombination lines in the Heisinglet system is expected to be relatively simple, supported by accurate atomic models. We examine the intensities of Heisingletsλ3614, λ3965, λ5016, λ6678, and λ7281 and the triplet Heiλ5876 in various types of ionized nebulae and compare them with theoretical predictions to test the validity of the “Case B” recombination scenario and the assumption of thermal homogeneity. Our analysis includes 85 spectra from Galactic and extragalactic Hiiregions, 90 from star-forming galaxies, and 218 from planetary nebulae, all compiled by the Deep Spectra of Ionized Regions Database Extended (DESIRED-E) project. By evaluating the ratios Heiλ7281/λ6678 and Heiλ7281/λ5876, we determineT_e(Hei) and compare it with direct measurements ofT_e([Oiii]λ4363/λ5007). We find thatT_e(Hei) is systematically lower thanT_e([Oiii]) across most objects and nebula types. Additionally, we identify a correlation between the abundance discrepancy factor (ADF(O²⁺)) and the differenceT_e([Oiii]) –T_e(Hei) for planetary nebulae. We explore two potential explanations: photon loss fromn¹P → 1¹Stransitions and temperature inhomogeneities. Deviations from “Case B” may indicate photon absorption by Hirather than Heiand/or generalized ionizing photon escape, highlighting the need for detailed consideration of radiative transfer effects. If temperature inhomogeneities are widespread, identifying a common physical phenomenon affecting all ionized nebulae is crucial. Our results suggest that both scenarios can contribute to the observed discrepancies. 

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4. 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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5. SN 2024ggi in NGC 3621: Rising Ionization in a Nearby, Circumstellar-material-interacting Type II Supernova

   https://doi.org/10.3847/1538-4357/ad5c64  

   Jacobson-Galán, W V; Davis, K W; Kilpatrick, C D; Dessart, L; Margutti, R; Chornock, R; Foley, R J; Arunachalam, P; Auchettl, K; Bom, C R; et al (September 2024, The Astrophysical Journal)

   Abstract We present UV–optical–near-infrared observations and modeling of supernova (SN) 2024ggi, a type II supernova (SN II) located in NGC 3621 at 7.2 Mpc. Early-time (“flash”) spectroscopy of SN 2024ggi within +0.8 days of discovery shows emission lines of Hi, Hei, Ciii, and Niiiwith a narrow core and broad, symmetric wings (i.e., “IIn-like”) arising from the photoionized, optically thick, unshocked circumstellar material (CSM) that surrounded the progenitor star at shock breakout (SBO). By the next spectral epoch at +1.5 days, SN 2024ggi showed a rise in ionization as emission lines of Heii, Civ, Niv/v, and Ovbecame visible. This phenomenon is temporally consistent with a blueward shift in the UV–optical colors, both likely the result of SBO in an extended, dense CSM. The IIn-like features in SN 2024ggi persist on a timescale oft_IIn= 3.8 ± 1.6 days, at which time a reduction in CSM density allows the detection of Doppler-broadened features from the fastest SN material. SN 2024ggi has peak UV–optical absolute magnitudes ofM_w2= −18.7 mag andM_g= −18.1 mag, respectively, that are consistent with the known population of CSM-interacting SNe II. Comparison of SN 2024ggi with a grid of radiation hydrodynamics and non–local thermodynamic equilibrium radiative-transfer simulations suggests a progenitor mass-loss rate of $\dot{M}={10}^{-2}{M}_{\odot }$yr⁻¹(v_w= 50 km s⁻¹), confined to a distance ofr< 5 × 10¹⁴cm. Assuming a wind velocity ofv_w= 50 km s⁻¹, the progenitor star underwent an enhanced mass-loss episode in the last ∼3 yr before explosion. 

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