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1. Mechanochemical Reactivity of a Multimodal 2H-Bis-Naphthopyran Mechanophore

   https://doi.org/10.1039/d3py00344b  

   Osler, Skylar K.; McFadden, Molly E.; Zeng, Tian; Robb, Maxwell J. (June 2023, Polymer Chemistry)

   Multimodal mechanophores that react under mechanical force to produce discrete product states with uniquely coupled absorption properties are interesting targets for the design of force-sensing polymers. Herein, we investigate the reactivity of a 2H-bis-naphthopyran mechanophore that generates thermally persistent mono-merocyanine and bis-merocyanine products upon mechanical activation in solution using ultrasonication, distinct from the thermally reversible products generated photochemically. We demonstrate that a force-mediated ester C(O)–O bond scission reaction following ring opening establishes an intramolecular hydrogen bond, locking one merocyanine subunit in the open form. Model compound studies suggest that this locked subunit confers remarkable thermal stability to bis-merocyanine isomers possessing a trans exocyclic alkene on the other subunit, implicating the formation of an unusual trans merocyanine isomer as the product of mechanochemical activation. Density functional theory calculations unexpectedly predict a thermally reversible retro-cyclization reaction of the bis-merocyanine species that could explain the mechanochemical generation of the unusual trans merocyanine isomer. 

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2. IBX Oxidations for the Synthesis of Substituted 2H-Pyrans

   https://doi.org/10.3987/COM-20-S(K)69  

   R. Williams, David; A. Bawel, Seth; Haddadpour, Nazanin; Maier, Sarah (January 2021, HETEROCYCLES)
3. Control of interlayer physics in 2H transition metal dichalcogenides

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4. Lithiation in 2H-MoTe ₂ Nanoflakes

   https://doi.org/10.1021/acs.chemmater.4c01517  

   Xu, Shiyu; Williams, Natalie L; Lee, Sihun; Huang, Jason J; Siddique, Saif; Singer, Andrej; Cha, Judy J (October 2024, Chemistry of Materials)
5. Hybrid Organic–Inorganic Halide Derivatives of the 2H Hexagonal Perovskite Structure

   https://doi.org/10.1021/acs.chemmater.2c00688  

   Holzapfel, Noah P.; Milder, Alexander; Woodward, Patrick M. (September 2022, Chemistry of Materials)

   Four quaternary hybrid halide perovskites have been synthesized in hydrohalic acid solutions under hydrothermal conditions. The structures of (CH3NH3)2AgRhX6 and (CH3NH3)2NaRhX6, (X = Cl–, Br–) consist of infinite one-dimensional chains of face-sharing metal-halide octahedra. The structure is closely related to the 2H hexagonal perovskite structure, but the space group symmetry is lowered from hexagonal P63/mmc to trigonal P3 ̅m1 by site ordering of the Rh3+ and Ag+/Na+ cations. All compositions demonstrate broad-spectrum visible light absorption with optical transitions arising from rhodium d-to-d transitions and halide-to-rhodium charge transfer transitions. The bromides show a 0.2 eV red shift in the optical transitions compared to the analogous chlorides. Crystal field splitting energies were found to be 2.6 eV and 2.4 eV for the chloride and bromide compositions, respectively. Band structure calculations for all compositions give rather flat valence and conduction bands, suggesting a zero-dimensional electronic structure. The valence bands are made up of crystal orbitals that are almost exclusively Rh 4d–Cl 3p (Br 4p) π* in character, while the conduction bands have Rh 4d–Cl 3p (Br 4p) σ* character. 

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