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1. Seismological expression of the iron spin crossover in ferropericlase in the Earth’s lower mantle

   https://doi.org/10.1038/s41467-021-26115-z  

   Shephard, Grace E.; Houser, Christine; Hernlund, John W.; Valencia-Cardona, Juan J.; Trønnes, Reidar G.; Wentzcovitch, Renata M. (October 2021, Nature Communications)

   Abstract The two most abundant minerals in the Earth’s lower mantle are bridgmanite and ferropericlase. The bulk modulus of ferropericlase (Fp) softens as iron d-electrons transition from a high-spin to low-spin state, affecting the seismic compressional velocity but not the shear velocity. Here, we identify a seismological expression of the iron spin crossover in fast regions associated with cold Fp-rich subducted oceanic lithosphere: the relative abundance of fast velocities in P- and S-wave tomography models diverges in the ~1,400-2,000 km depth range. This is consistent with a reduced temperature sensitivity of P-waves throughout the iron spin crossover. A similar signal is also found in seismically slow regions below ~1,800 km, consistent with broadening and deepening of the crossover at higher temperatures. The corresponding inflection in P-wave velocity is not yet observed in 1-D seismic profiles, suggesting that the lower mantle is composed of non-uniformly distributed thermochemical heterogeneities which dampen the global signature of the Fp spin crossover. 

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2. DNA T-shaped crossover tiles for 2D tessellation and nanoring reconfiguration

   https://doi.org/10.1038/s41467-023-43558-8  

   Yang, Qi; Chang, Xu; Lee, Jung Yeon; Saji, Minu; Zhang, Fei (November 2023, Nature Communications)

   Abstract DNA tiles serve as the fundamental building blocks for DNA self-assembled nanostructures such as DNA arrays, origami, and designer crystals. Introducing additional binding arms to DNA crossover tiles holds the promise of unlocking diverse nano-assemblies and potential applications. Here, we present one-, two-, and three-layer T-shaped crossover tiles, by integrating T junction with antiparallel crossover tiles. These tiles carry over the orthogonal binding directions from T junction and retain the rigidity from antiparallel crossover tiles, enabling the assembly of various 2D tessellations. To demonstrate the versatility of the design rules, we create 2-state reconfigurable nanorings from both single-stranded tiles and single-unit assemblies. Moreover, four sets of 4-state reconfiguration systems are constructed, showing effective transformations between ladders and/or rings with pore sizes spanning ~20 nm to ~168 nm. These DNA tiles enrich the design tools in nucleic acid nanotechnology, offering exciting opportunities for the creation of artificial dynamic DNA nanopores. 

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3. Conformational dynamics modulating electron transfer

   https://doi.org/10.1063/5.0102707  

   Matyushov, Dmitry V. (September 2022, The Journal of Chemical Physics)

   Diffusional dynamics of the donor–acceptor distance are responsible for the appearance of a new time scale of diffusion over the distance of electronic tunneling in electron-transfer reactions. The distance dynamics compete with the medium polarization dynamics in the dynamics-controlled electron-transfer kinetics. The pre-exponential factor of the electron-transfer rate constant switches, at the crossover distance, between a distance-independent, dynamics-controlled plateau and exponential distance decay. The crossover between two regimes is controlled by an effective relaxation time slowed down by a factor exponentially depending on the variance of the donor–acceptor displacement. Flexible donor–acceptor complexes must show a greater tendency for dynamics-controlled electron transfer. Energy chains based on electron transport are best designed by placing the redox cofactors near the crossover distance. 

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4. Dynamic-dependent selectivity in a bisphosphine iron spin crossover C–H insertion/π-coordination reaction

   https://doi.org/10.1039/D3SC02078A  

   Davenport, Michael T; Kirkland, Justin K; Ess, Daniel H (September 2023, Chemical Science)

   Organometallic reaction selectivity is governed by dynamic motion rather than transition states or spin crossover. 

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5. Electronic transport properties of spin-crossover polymer plus polyaniline composites with Fe ₃ O ₄ nanoparticles

   https://doi.org/10.1088/2515-7639/ad1b35  

   Mishra, Esha; Chin, WaiKiat; McElveen, Kayleigh A.; Ekanayaka, Thilini K.; Zaz, M. Zaid; Viswan, Gauthami; Zielinski, Ruthi; N’Diaye, Alpha T.; Shapiro, David; Lai, Rebecca Y.; et al (January 2024, Journal of Physics: Materials)

   Abstract Adding Fe₃O₄nanoparticles to composites of [Fe(Htrz)₂(trz)](BF₄) spin-crossover polymer and polyaniline (PANI) drives a phase separation of both and restores the molecular structure and cooperative effects of the spin-crossover polymer without compromising the increased conductivity gained through the addition of PANI. We observe an increased on-off ratio for the DC conductivity owing to an enlarged off state resistivity and a 20 times larger AC conductivity of the on state compared with DC values. The Fe₃O₄nanoparticles, primarily confined to the [Fe(Htrz)₂(trz)](BF₄) phase, are ferromagnetically coupled to the local moment of the spin-crossover molecule suggesting the existence of an exchange interaction between both components. 

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