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Nissen Richards posted an update 9 days ago
Fractals are of fundamental importance in science and technology. Theoretical simulations indicate that Sierpiński triangles (STs) possess specific optical and electronic properties. To study their properties and uncover their potential applications, it is necessary to pack STs into large-scale two-dimensional crystalline structures. Here, a series of ordered structures consisting of ST units are successfully constructed on gold surfaces through coordination between 1,3-bis(4-pyridyl) benzene molecules and Fe atoms. Crystals of STs are characterized by scanning tunneling microscopy. K-map analysis explains the structural formation mechanism, which is further verified by density functional theory calculations. The molecular free diffusion and nice structure matching between STs and gold surfaces play important roles in the formation of crystals of STs.A highly selective and general photoinduced C-Cl borylation protocol that employs [Ni(IMes)2] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes is reported. This photoinduced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B2pin2 at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)2] undergoes very fast chlorine atom abstraction from aryl chlorides to give [NiI(IMes)2Cl] and aryl radicals. Control experiments indicate that light promotes the reaction of [NiI(IMes)2Cl] with aryl chlorides generating additional aryl radicals and [NiII(IMes)2Cl2]. The aryl radicals react with an anionic sp2-sp3 diborane [B2pin2(OMe)]- formed from B2pin2 and KOMe to yield the corresponding borylation product and the [Bpin(OMe)]•- radical anion, which reduces [NiII(IMes)2Cl2] under irradiation to regenerate [NiI(IMes)2Cl] and [Ni(IMes)2] for the next catalytic cycle.Lead toxicity is hindering the applications of conventional lead halide perovskites (PVKs), and antimony (Sb) is a promising nontoxic Pb alternative, showing huge potential in optoelectronic devices. Herein, pure and Mn-doped Cs3Sb2Cl9 crystals are synthesized in a facile route and studied both experimentally and theoretically. All the pure and Mn-doped Cs3Sb2Cl9 crystals show good crystallinity and similar crystal structures, exhibiting visible photoluminescence (PL) characteristics with emission peaks at 422 and 613 nm, respectively. Combined density functional theory (DFT) calculations and experimental analyses reveal that the structure of the host PVK compound Cs3Sb2Cl9 is not influenced by the formation of [MnCl6]4- octahedra and that Mn 3d orbitals generate impurity states in the forbidden energy gap of Cs3Sb2Cl9. Therefore, energy transfer from Cs3Sb2Cl9 to Mn 3d states is observed, resulting in the d-d transition and bright red luminescence. Mn-doped Sb-based PVK can be utilized as a new platform for optoelectronic applications.Phosphangulene (1) is a hexacyclic triarylphosphine with a distinctive conical shape and other features that allow the compound to be viewed from diverse perspectives and to be embraced by chemists from different parts of the field as a molecule worthy of special attention. In recent work, phosphangulene and its derivatives have proven to be effective tools for probing general principles that govern molecular organization in solids. The phosphangulene family is particularly well-suited for these studies because systematic structural changes in the compounds are easy to introduce. In crystals of phosphangulene itself, molecules are stacked efficiently like hats, giving rise to an R3m structure that is polar and pyroelectric. Simple conversion of the compound into phosphangulene oxide (7a) or other chalcogenides blocks effective stacking and forces crystallization to produce alternative structures that have many suboptimal intermolecular interactions and vary little in energy as their geometries are altered. Thular components can be varied without imposing severe energetic penalties.Because substituted members of the phosphangulene family have awkward curved shapes that cannot be packed efficiently, they have emerged as highly effective partners for cocrystallizing fullerenes and for using concave-convex interactions to control how fullerenes can be organized in materials. This can be achieved without eliminating fullerene-fullerene contacts of the type needed to ensure conductivity. In addition, phosphangulene has created unlimited opportunities for making complex structures with large curved aromatic surfaces based on a new strategy in which the central atom of phosphorus is used to form covalent bonds with other elements or to introduce coordinative interactions with metals. In these ways, recent work has put phosphangulene in the spotlight as a compound of unusually broad interest and shown that it can appropriately be called a molecule for all chemists.Calcium cobaltite (Ca3Co4O9) is a promising p-type thermoelectric oxide material. Here, we present an approach to optimize the thermoelectric performance of Ca3Co4O9 by controlling the chemical composition and fabrication process. Ca3-xBi x Co3.92O9+δ (0.1 ≤ x ≤ 0.3) and Ca2.7Bi0.3Co y O9+δ (3.92 ≤ y ≤ 4.0) ceramics were prepared by Spark Plasma Sintering (SPS). Ipilimumab supplier Stoichiometric mixtures of raw materials were combined and calcined at 1203 K for 12 h, followed by SPS at 1023 K for 5 min at 50 MPa. The samples were subsequently annealed at 1023 or 1203 K for 12 h in air. XRD and HRTEM analyses confirmed the formation of the cobaltite misfit phase with minor amounts of secondary phases; SEM-EDS showed the presence of Bi-rich and Co-rich secondary phases. After annealing at 1203 K, the secondary phases were significantly reduced. By controlling the cobalt deficiency and level of bismuth substitution, the electrical conductivity was enhanced without degrading Seebeck coefficients, promoting a high power factor of 0.34 mW m-1 K-2 at 823 K (parallel to the ab planes, //ab). Due to enhanced phonon scattering, the thermal conductivity was reduced by 20%. As a result, a highly competitive ZT(//ab) of 0.16 was achieved for Ca2.7Bi0.3Co3.92O9+δ ceramics at 823 K.