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1. Preparation and Characterization of N , N′ ‐Dialkyl‐1,3‐propanedialdiminium Chlorides, N , N′ ‐Dialkyl‐1,3‐propanedialdimines, and Lithium N , N′ ‐Dialkyl‐1,3‐propanedialdiminates

   https://doi.org/10.1002/hlca.202200152  

   Schmit, Claire E.; Girolami, Gregory S. (May 2023, Helvetica Chimica Acta)

   Abstract We describe convenient preparations ofN,N′‐dialkyl‐1,3‐propanedialdiminium chlorides,N,N′‐dialkyl‐1,3‐propanedialdimines, and lithiumN,N′‐dialkyl‐1,3‐propanedialdiminates in which the alkyl groups are methyl, ethyl, isopropyl, ortert‐butyl. For the dialdiminium salts, the N₂C₃backbone is always in thetrans‐s‐transconfiguration. Three isomers are present in solution except for thetert‐butyl compound, for which only two isomers are present; increasing the steric bulk of theN‐alkyl substituents shifts the equilibrium away from the (Z,Z) isomer in favor of the (E,Z), and (E,E) isomers. For the neutral dialdimines, crystal structures show that the methyl and isopropyl compounds adopt the (E,Z) form, whereas thetert‐butyl compound is in the (E,E) form. In aprotic solvents all four dialdimines (as well as the lithium dialdiminate salts) adoptcis‐s‐cisconformations in which there presumably is either an intramolecular hydrogen bond (or a lithium cation) between the two nitrogen atoms. 

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2. Recyclable All‐in‐One Organo‐Photo‐Auxiliaries Enabling ( sp ³ )C−( sp ³ )C Coupling Reactions with Diverse Functionalities

   https://doi.org/10.1002/adsc.202400899  

   Maharjan, Samjhana; Dakoju, Ravi_Kishore; Albano, Bella; Ondiek, Pamela_A; O'Shea, Joseph_M; Cosme‐Hernandez, Angel_G; Wink, Donald; Pemberton, Barry_C; Lopez, Steven_A; Ayitou, A_Jean‐Luc (November 2024, Advanced Synthesis & Catalysis)

   Abstract Photochemical C−C coupling reactions can be tailored to industrial chemical processes and preparations of pharmaceuticals. Recent approaches in this area are limited to using precious transition metal coordination complexes that facilitate light absorption and redox processes with benchtop chemicals. Herein, we propose a paradigm that involves all‐in‐one organo‐photo‐auxiliaries,thio‐heteroarenes, which exhibit unique photophysical properties. Thesethio‐heteroarenes were employed to prepare several all‐in‐one ionic photo‐salts from commercially available alkyl/benzyl and heterocyclic halides via aromaticity‐mediated nucleophilic substitution reactions. From the library of >30 salts, we performed on‐demand photochemical C−C coupling reactions to isolate numerous symmetrical and unsymmetrical diary/alkyl‐ethanes with yields up to 84% and mass balance as high as 96%. We also investigated the influence of structural features/properties on the outcomes of the photochemical C−C coupling reactions. The current photochemical C−C method was successful in the isolation of >30 photoproducts, including the natural product Brittonin A, a precursor of Imipramine, and derivatives of the bioactive Honokiol Analogues. Furthermore, transient absorption spectroscopy and time‐dependent density functional theory calculations were used to decipher the nature of light‐promoted electronic transitions. 

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3. Searles Lake evaporite sequences: Indicators of late Pleistocene/Holocene lake temperatures, brine evolution, and p CO2

   https://doi.org/10.1130/B35857.1  

   Olson, Kristian J.; Lowenstein, Tim K. (March 2021, GSA Bulletin)

   null (Ed.)

   Searles Lake, California, was a saline-alkaline lake that deposited >25 non-clastic minerals that record the history of lake chemistry and regional climate. Here, the mineralogy and petrography from the late Pleistocene/Holocene (32−6 ka) portion of a new Searles Lake sediment core, SLAPP-SRLS17, is combined with thermodynamic models to determine the geochemical and paleoclimate conditions required to produce the observed mineral phases, sequences, and abundances. The models reveal that the primary precipitates formed by open system (i.e., fractional crystallization), whereas the early diagenetic salts formed by salinity-driven closed system back-reactions (i.e., equilibrium crystallization). For core SLAPP-SRLS17, the defining evaporite sequence trona → burkeite → halite indicates brine temperatures within a 20−29 °C range, implying thermally insulating lake depths >10 m during salt deposition. Evaporite phases reflect lake water pCO2 consistent with contemporaneous atmospheric values of ∼190−270 ppmv. However, anomalous layers of nahcolite and thenardite indicate pulses of pCO2 > 700−800 ppm, likely due to variable CO2 injection along faults. Core sedimentology indicates that Searles Lake was continuously perennial between 32 ka and 6 ka such that evaporite units reflect periods of net evaporation but never complete desiccation. Model simulations indicate that cycles of partial evaporation and dilution strongly influence long-term brine evolution by amassing certain species, particularly Cl−, that only occur in late-stage soluble salts. A model incorporating long-term brine dynamics corrects previous mass-balance anomalies and shows that the late Pleistocene/Holocene (32−6 ka) salts are partially inherited from the solutes introduced into earlier lakes going back at least 150 ka. 

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4. Salts accelerate the switching kinetics of a cyclobis(paraquat- p -phenylene) [2]rotaxane

   https://doi.org/10.1039/c9ob00085b  

   Andersen, Sissel S.; Saad, Afaf W.; Kristensen, Rikke; Pedersen, Teis S.; O'Driscoll, Luke J.; Flood, Amar H.; Jeppesen, Jan O. (February 2019, Organic & Biomolecular Chemistry)

   The rate at which the macrocyclic cyclobis(paraquat- p -phenylene) ring of a bistable [2]rotaxane moves from a tetrathiafulvalene station to an oxyphenylene station upon oxidation of the tetrathiafulvalene station is found to be increased in the presence of added salts. Compared to the salt-free case, 0.1 M solutions of a series of tetraalkylammonium hexafluorophosphate salts (R 4 N·PF 6 , R = H, Me, Et or n -Bu) and of tetrabutylammonium perchlorate ( n -Bu 4 N·ClO 4 ) all afford an increased switching rate, which is largest in the case of n -Bu 4 N·ClO 4 with smaller anions. Variation in the size of the ammonium cation has no significant effect. These results indicate that the addition of excess ions can be used as an accelerator to speed up shuttling processes in rotaxanes and catenanes based on the mobile cyclobis(paraquat- p -phenylene) ring, and that the choice of anion offers a convenient means of controlling the extent of this effect. 

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5. Very thermostable energetic materials based on a fused-triazole: 3,6-diamino-1 H -[1,2,4]triazolo[4,3- b ][1,2,4]triazole

   https://doi.org/10.1039/d0nj05152g  

   Tang, Yongxing; An, Ziwei; Chinnam, Ajay Kumar; Staples, Richard J.; Shreeve, Jean'ne M. (January 2021, New Journal of Chemistry)

   null (Ed.)

   3,6-Diamino-1 H -[1,2,4]triazolo[4,3- b ][1,2,4]triazole ( 1 ) and its energetic salts ( 2–9 ) were designed and synthesized based on a fused-triazole backbone with two C-amino groups as substituents. Their physicochemical and energetic properties were measured or calculated. Among them, compound 1 exhibits superior thermostability ( T d (onset) : 261 °C), surpassing its analogues 3,7-diamino-7 H -[1,2,4]triazolo[4,3- b ][1,2,4]triazole (DATT, 219 °C) and 3,6,7-triamino-7 H -[1,2,4]triazolo[4,3- b ][1,2,4]triazole (TATOT, 245 °C). The differences in thermal stabilities were further investigated by determining the lowest bond dissociation energies (BDE) where a positive correlation between the stability of the molecules and the lowest BDE values is observed. The results show that 1 with the highest value for the lowest BDE has a superior thermostability in comparison to DATT and TATOT. The energetic salts ( 2–9 ) also exhibit remarkable thermal stabilities as well as low impact and friction sensitivities. The fused-triazole backbone 1 H -[1,2,4]triazolo[4,3- b ][1,2,4]triazole with two C-amino groups as substituents is shown to be a promising building block for construction of very thermally stable energetic materials. 

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