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1. On the reciprocal relationship between σ-hole bonding and (anti)aromaticity gain in ketocyclopolyenes

   https://doi.org/10.1039/D0OB01076F  

   Paudel, Hari Ram; Karas, Lucas José; Wu, Judy I-Chia (July 2020, Organic & Biomolecular Chemistry)

   null (Ed.)

   σ-Hole bonding interactions ( e.g. , tetrel, pnictogen, chalcogen, and halogen bonding) can polarize π-electrons to enhance cyclic [4 n ] π-electron delocalization ( i.e. , antiaromaticity gain) or cyclic [4 n + 2] π-electron delocalization ( i.e. , aromaticity gain). Examples based on the ketocyclopolyenes: cyclopentadienone, tropone, and planar cyclononatetraenone are presented. Recognizing this relationship has implications, for example, for tuning the electronic properties of fulvene-based π-conjugated systems such as 9-fluorenone. 

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2. The Atacama Cosmology Telescope: DR6 power spectra, likelihoods and ΛCDM parameters

   https://doi.org/10.1088/1475-7516/2025/11/062  

   Louis, Thibaut; La_Posta, Adrien; Atkins, Zachary; Jense, Hidde T; Abril-Cabezas, Irene; Addison, Graeme E; Ade, Peter AR; Aiola, Simone; Alford, Tommy; Alonso, David; et al (November 2025, Journal of Cosmology and Astroparticle Physics)

   Abstract We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg²of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower thanPlanckin polarization. We find that the ACT angular power spectra estimated over 10,000 deg², and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the ΛCDM model. Combining ACT with larger-scalePlanckdata, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe. We find similar constraining power, and consistent results, from either thePlanckpower spectra or from ACT combined withWMAPdata, as well as from either temperature or polarization in the joint P-ACT dataset. When combined with CMB lensing from ACT andPlanck, and baryon acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI DR1), we measure a baryon density of Ω_bh²= 0.0226 ± 0.0001, a cold dark matter density of Ω_ch²= 0.118 ± 0.001, a Hubble constant ofH₀= 68.22 ± 0.36 km/s/Mpc, a spectral index ofn_s= 0.974 ± 0.003, and an amplitude of density fluctuations ofσ₈= 0.813 ± 0.005. Including the DESI DR2 data tightens the Hubble constant toH₀= 68.43 ± 0.27 km/s/Mpc; ΛCDM parameters agree between the P-ACT and DESI DR2 data at the 1.6σlevel. We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness. The contribution from Sunyaev-Zel'dovich (SZ) anisotropy is detected at high significance; we find evidence for a tilt with suppressed small-scale power compared to our baseline SZ template spectrum, consistent with hydrodynamical simulations with feedback. 

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3. 2 kV Al _0.64 Ga _0.36 N-channel high electron mobility transistors with passivation and field plates

   https://doi.org/10.35848/1882-0786/ad9db4  

   Alam, Md Tahmidul; Chen, Jiahao; Stephenson, Kenneth; Mamun, Md Abdullah-Al; Mazumder, Abdullah_Al Mamun; Pasayat, Shubhra S; Khan, Asif; Gupta, Chirag (January 2025, Applied Physics Express)

   Abstract High voltage (∼2 kV) Al_0.64Ga_0.36N-channel high electron mobility transistors were fabricated with an on-resistance of ∼75 Ω. mm (∼21 mΩ. cm²). Two field plates of variable dimensions were utilized to optimize the breakdown voltage. The breakdown voltage reached >3 kV (tool limit) before passivation however it reduced to ∼2 kV after Si₃N₄surface passivation and field plate deposition. The breakdown voltage and on-resistance demonstrated a strong linear correlation in a scattered plot of ∼50 measured transistors. The fabricated transistors were electrically characterized and benchmarked against the state-of-the-art high-voltage (> 1 kV) Al-rich (>40%) AlGaN-channel transistors in breakdown voltage and on-resistance, indicating significant progress. 

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4. Competition Between the Two σ‐Holes in the Formation of a Chalcogen Bond

   https://doi.org/10.1002/cphc.202200936  

   Scheiner, Steve (February 2023, ChemPhysChem)

   Abstract A chalcogen atom Y contains two separate σ‐holes when in a R₁YR₂molecular bonding pattern. Quantum chemical calculations consider competition between these two σ‐holes to engage in a chalcogen bond (ChB) with a NH₃base. R groups considered include F, Br, I, and tert‐butyl (tBu). Also examined is the situation where the Y lies within a chalcogenazole ring, where its neighbors are C and N. Both electron‐withdrawing substituents R₁and R₂act cooperatively to deepen the two σ‐holes, but the deeper of the two holes consistently lies opposite to the more electron‐withdrawing group, and is also favored to form a stronger ChB. The formation of two simultaneous ChBs in a triad requires the Y atom to act as double electron acceptor, and so anti‐cooperativity weakens each bond relative to the simple dyad. This effect is such that some of the shallower σ‐holes are unable to form a ChB at all when a base occupies the other site. 

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5. Collision cross‐section analysis of self‐assembled metallomacrocycle isomers and isobars via ion mobility mass spectrometry

   https://doi.org/10.1002/rcm.8717  

   Endres, Kevin_J; Barthelmes, Kevin; Winter, Andreas; Antolovich, Robert; Schubert, Ulrich_S; Wesdemiotis, Chrys (February 2020, Rapid Communications in Mass Spectrometry)

   RationaleCoordinatively driven self‐assembly of transition metal ions and bidentate ligands gives rise to organometallic complexes that usually contain superimposed isobars, isomers, and conformers. In this study, the double dispersion ability of ion mobility mass spectrometry (IM‐MS) was used to provide a comprehensive structural characterization of the self‐assembled supramolecular complexes by their mass and charge, revealed by the MS event, and their shape and collision cross‐section (Ω), revealed by the IM event. MethodsSelf‐assembled complexes were synthesized by reacting a bis(terpyridine) ligand exhibiting a 60^odihedral angle between the two ligating terpyridine sites (T) with divalent Zn, Ni, Cd, or Fe. The products were isolated as (Metal²⁺[T])_n(PF₆)_2nsalts and analyzed using IM‐MS after electrospray ionization (ESI) which produced several charge states from eachn‐mer, depending on the number of PF₆ˉ anions lost upon ESI. Experimental Ω data, derived using IM‐MS, and computational Ω predictions were used to elucidate the size and architecture of the complexes. ResultsOnly macrocyclic dimers, trimers, and tetramers were observed with Cd²⁺, whereas Zn²⁺formed the same plus hexameric complexes. These two metals led to the simplest product distributions and no linear isomers. In sharp contrast, Ni²⁺and Fe²⁺formed all possible ring sizes from dimer to hexamer as well as various linear isomers. The experimental and theoretical Ω data indicated rather planar macrocyclic geometries for the dimers and trimers, twisted 3D architectures for the larger rings, and substantially larger sizes with spiral conformation for the linear congeners. Adding PF₆ˉ to the same complex was found to mainly cause size contraction due to new stabilizing anion–cation interactions. ConclusionsComplete structural identification could be accomplished using ESI‐IM‐MS. Our results affirm that self‐assembly with Cd²⁺and Zn²⁺proceeds through reversible equilibria that generate the thermodynamically most stable structures, encompassing exclusively macrocyclic architectures that readily accommodate the 60^oligand used. In contrast, complexation with Ni²⁺and Fe²⁺, which form stronger coordinative bonds, proceeds through kinetic control, leading to more complex mixtures and kinetically trapped less stable architectures, such as macrocyclic pentamers and linear isomers. 

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