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1. Pyridinium 3-nitrobenzoate–3-nitrobenzoic acid (1/1)

   https://doi.org/10.1107/S2414314621005812  

   Howarth, Alexis; Barbosa, Tony J.; Zeller, Matthias; Hillesheim, Patrick C. (June 2021, IUCrData)

   null (Ed.)

   The crystal structure of the product of the neutralization reaction between 3-nitrobenzoic acid and pyridine is reported. The entities that crystallized are a pyridinium cation, a 3-nitrobenzoate anion and a 3-nitrobenzoic acid molecule in a 1:1:1 molar ratio, C 5 H 6 N + ·C 7 H 4 NO 4 − ·C 7 H 5 NO 4 . Distinct sets of hydrogen bonds link the pyridinium and benzoate ions (N—H...O) and the acid and benzoate moieties (O—H...O). The hydrogen bonding along with π–π stacking between the acid and benzoate moieties accounts for the long-range ordering of the crystal. 

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2. Aromaticity and Photoreactivity of 4‐ and 3‐Nitrenopyridine 1‐Oxides and Phenylnitrene

   https://doi.org/10.1002/poc.70035  

   Wasson, Fiona J; Borah, Anindya; Govorov, Dmitrii; Mendis, W Dinindu; Poole, James S; Ault, Bruce S; Karney, William L; Gudmundsdottir, Anna D (October 2025, Journal of Physical Organic Chemistry)

   ABSTRACT The pursuit of sustainable organic synthesis has renewed interest in photochemistry, as sunlight‐driven reactions provide eco‐friendly alternative methods. Although the relationships among structure, properties, and reactivity are well established for ground‐state molecules, the understanding of excited states and reactive intermediates, such as triplet and singlet arylnitrenes, remains limited. Herein, we investigated the properties of triplet and singlet 4‐nitrenopyridine‐1‐pyridine oxide (1N), 3‐nitrenopyridine‐1‐pyridine oxide (2N), and phenylnitrene (PhN) using density functional theory (DFT), complete active space self‐consistent field (CASSCF(10,9)), and complete active space second‐order perturbation theory (CASPT2(10,9)) calculations. Bond length analysis demonstrated that³1Nand¹1N, as well as¹2Nand¹PhN, exhibit significant imine biradical character, whereas the structures of³2Nand³PhNare better described as benzene‐like. Nucleus‐independent chemical shift (NICS(0), NICS(1.7)_ZZ) and anisotropy of induced current density (ACID) calculations were performed to compare the induced magnetic currents in these molecules. These analyses demonstrated that³1Nis weakly aromatic, whereas³2Nand³PhNare best described as having Baird aromaticity. In contrast, singlet nitrenes¹1N,¹2N, and¹PhNare nonaromatic. In addition, irradiation of1in argon matrices verified that³1Nreacts photochemically to form corresponding ketenimine1K. Finally, the absorption difference spectrum of³1Nin a frozen 2‐methyltetrahydrofuran (mTHF) matrix exhibited resolved vibrational structure, suggesting the vibrational coupling to another electronic state. These insights into the structure and aromaticity of heterocyclic nitrenes could provide new avenues for modulating the reactivity of triplet ground state and triplet excited molecules. 

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3. Structure and motifs of iron oxides from 1 to 3 TPa

   https://doi.org/10.1103/PhysRevMaterials.6.043602  

   Zheng, Feng; Sun, Yang; Wang, Renhai; Fang, Yimei; Zhang, Feng; Da, Bo; Wu, Shunqing; Wang, Cai-Zhuang; Wentzcovitch, Renata M.; Ho, Kai-Ming (April 2022, Physical Review Materials)
4. Dissolution of Complex Metal Oxides from First-Principles and Thermodynamics: Cation Removal from the (001) Surface of Li(Ni _1/3 Mn _1/3 Co _1/3 )O ₂

   https://doi.org/10.1021/acs.est.8b00054  

   Bennett, Joseph W.; Jones, Diamond; Huang, Xu; Hamers, Robert J.; Mason, Sara E. (April 2018, Environmental Science & Technology)
5. Photolysis of 3‐Azido‐3‐phenyl‐3 H ‐isobenzofuran‐1‐one at Ambient and Cryogenic Temperatures ^†

   https://doi.org/10.1111/php.13500  

   Thenna‐Hewa, Kosala; Sebastien, William; Lemen, Elaine M.; Karney, William L.; Abe, Manabu; Gudmundsdottir, Anna D. (August 2021, Photochemistry and Photobiology)

   Abstract Although alkyl azides are known to typically form imines under direct irradiation, the product formation mechanism remains ambiguous as some alkyl azides also yield the corresponding triplet alkylnitrenes at cryogenic temperatures. The photoreactivity of 3‐azido‐3‐phenyl‐3H‐isobenzofuran‐1‐one (1) was investigated in solution and in cryogenic matrices. Irradiation (λ = 254 nm) of azide 1 in acetonitrile yielded a mixture of imines 2 and 3. Monitoring of the reaction progress using UV‐Vis absorption spectroscopy revealed an isosbestic point at 210 nm, indicating that the reaction proceeded cleanly. Similar results were observed for the photoreactivity of azide 1 in a frozen 2‐methyltetrahydrofuran (mTHF) matrix. Irradiation of azide 1 in an argon matrix at 6 K resulted in the disappearance of its IR bands with the concurrent appearance of IR bands corresponding to imines 2 and 3. Thus, it was theorized that azide 1 forms imines 2 and 3 via a concerted mechanism from its singlet excited state or through singlet alkylnitrene¹1N, which does not intersystem cross to its triplet configuration. This proposal was supported by CASPT2 calculations on a model system, which suggested that the energy gap between the singlet and triplet configurations of alkylnitrene 1N is 33 kcal/mol, thus making intersystem crossing inefficient. 

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