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1. Expansion of the (BB)Ru metallacycle with coinage metal cations: formation of B–M–Ru–B (M = Cu, Ag, Au) dimetalacyclodiboryls

   https://doi.org/10.1039/C8SC00190A  

   Eleazer, Bennett J.; Smith, Mark D.; Popov, Alexey A.; Peryshkov, Dmitry V. (January 2018, Chemical Science)

   In this work, we introduce a novel approach for the selective assembly of heterometallic complexes by unprecedented coordination of coinage metal cations to strained single ruthenium–boron bonds on a surface of icosahedral boron clusters. M( i ) cations (M = Cu, Ag, and Au) insert into B–Ru bonds of the (BB)–carboryne complex of ruthenium with the formation of four-membered B–M–Ru–B metalacycles. Results of theoretical calculations suggest that bonding within these metalacycles can be best described as unusual three-center-two-electron B–M⋯Ru interactions that are isolobal to B–H⋯Ru borane coordination for M = Cu and Ag, or the pairs of two-center-two electron B–Au and Au–Ru interactions for M = Au. These transformations comprise the first synthetic route to exohedral coinage metal boryl complexes of icosahedral closo -{C 2 B 10 } clusters, which feature short Cu–B (2.029(2) Å) and Ag–B (2.182(3) Å) bonds and the shortest Au–B bond (2.027(2) Å) reported to date. The reported heterometallic complexes contain Cu( i ) and Au( i ) centers in uncharacteristic square-planar coordination environments. These findings pave the way to rational construction of a broader class of multimetallic architectures featuring M–B bonds. 

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2. Structure Directing Forces in Hybrid Layered Double Perovskites Containing Aromatic Organic Cations

   https://doi.org/10.1021/acs.cgd.3c01319  

   Race, Joseph T.; Liu, Tianyu; Woodward, Patrick M. (February 2024, Crystal Growth & Design)

   Hybrid n = 1 Ruddlesden-Popper perovskites with aromatic ammonium cations like benzylammonium (BzA) and phenethylammonium (PEA) have been shown to adopt polar structures and exhibit ferroelectricity, but many of the examples discovered thus far contain either Pb or Cd. Here, we describe the synthesis and structural characteriza-tion of four layered halide double perovskites: (BzA)4AgBiBr8, (PEA)4AgBiBr8, (BzA)4AgInCl8, and (PEA)4AgInCl8. In all four compounds the inorganic layers exhibit a chessboard ordering of Ag+ and Bi3+/In3+ and the layers stack in a coherent pattern that maintains the ordering over three-dimensional space. The octahedra sur-rounding Ag+ show a large axial compression, which results in much shorter bonds to the terminal halide ions than to the bridging halide ions, whereas the bismuth- and indium-centered octahedra show only small distortions. There appears to be a competition between polar distortions of the octahedra and octahedral tilting, both of which can optimize hydrogen bonding interactions between the ammonium cations and the inorganic layers. Unlike the Pb- or Cd-containing analogs, the double perovskites seem to favor patterns of octahedral tilting that suppress po-lar ordering of the organic cations. The packing of the organic cations depends on both their conformational flexi-bility and the lateral dimensions of the inorganic layer. These forces favor intra-layer edge-to-face interaction be-tween aromatic rings in the three of the four compounds. The lone exception is (PEA)4AgBiBr8, which forms weak inter-layer edge-to-face interactions between aromatic rings and slip-stacked packing within each organic layer. 

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3. Sr(Ag _1−x Li _x ) ₂ Se ₂ and [Sr ₃ Se ₂ ][(Ag _1−x Li _x ) ₂ Se ₂ ] Tunable Direct Band Gap Semiconductors

   https://doi.org/10.1002/anie.202301191  

   Zhou, Xiuquan; Wilfong, Brandon; Chen, Xinglong; Laing, Craig; Pandey, Indra R.; Chen, Ying‐Pin; Chen, Yu‐Sheng; Chung, Duck‐Young; Kanatzidis, Mercouri G. (February 2023, Angewandte Chemie International Edition)

   Abstract Synthesizing solids in molten fluxes enables the rapid diffusion of soluble species at temperatures lower than in solid‐state reactions, leading to crystal formation of kinetically stable compounds. In this study, we demonstrate the effectiveness of mixed hydroxide and halide fluxes in synthesizing complex Sr/Ag/Se in mixed LiOH/LiCl. We have accessed a series of two‐dimensional Sr(Ag_1−xLi_x)₂Se₂layered phases. With increased LiOH/LiCl ratio or reaction temperature, Li partially substituted Ag to form solid solutions of Sr(Ag_1−xLi_x)₂Se₂withxup to 0.45. In addition, a new type of intergrowth compound [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] was synthesized upon further reaction of Sr(Ag_1−xLi_x)₂Se₂with SrSe. Both Sr(Ag_1−xLi_x)₂Se₂and [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] exhibit a direct band gap, which increases with increasing Li substitution (x). Therefore, the band gap of Sr(Ag_1−xLi_x)₂Se₂can be precisely tuned via fine‐tuningxthat is controlled by only the flux ratio and temperature. 

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4. Lewis Acid‐Tethered (cAAC)–Copper Complexes: Reactivity for Hydride Transfer and Catalytic CO2 Hydrogenation

   https://doi.org/10.1002/anie.202411099  

   Song, Hayoung; Szymczak, Nathaniel Kolnik (July 2024, Angewandte Chemie International Edition)

   We present a series of borane‐tethered cyclic (alkyl)(amino)carbene (cAAC)‐copper complexes, including a borane‐capped Cu(I) hydride. This hydride is unusually hydridic and reacts rapidly with both CO2 and 2,6‐dimethylphenol at room temperature. Its reactivity is distinct from variants without a tethered borane, and the underlying principles governing the enhanced hydricity were evaluated experimentally and theoretically. These stoichiometric results were extended to catalytic CO2 hydrogenation, and the borane‐tethered (intramolecular) system exhibits ~3‐fold enhancement relative to an intermolecular system. 

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5. Materials Discovery of Stable and Nontoxic Halide Perovskite Materials for High‐Efficiency Solar Cells

   https://doi.org/10.1002/adfm.201804354  

   Jacobs, Ryan; Luo, Guangfu; Morgan, Dane (April 2019, Advanced Functional Materials)

   Abstract Two critical limitations of organic–inorganic lead halide perovskite materials for solar cells are their poor stability in humid environments and inclusion of toxic lead. In this study, high‐throughput density functional theory (DFT) methods are used to computationally model and screen 1845 halide perovskites in search of new materials without these limitations that are promising for solar cell applications. This study focuses on finding materials that are comprised of nontoxic elements, stable in a humid operating environment, and have an optimal bandgap for one of single junction, tandem Si‐perovskite, or quantum dot–based solar cells. Single junction materials are also screened on predicted single junction photovoltaic (PV) efficiencies exceeding 22.7%, which is the current highest reported PV efficiency for halide perovskites. Generally, these methods qualitatively reproduce the properties of known promising nontoxic halide perovskites that are either experimentally evaluated or predicted from theory. From a set of 1845 materials, 15 materials pass all screening criteria for single junction cell applications, 13 of which are not previously investigated, such as (CH₃NH₃)_0.75Cs_0.25SnI₃, ((NH₂)₂CH)Ag_0.5Sb_0.5Br₃, CsMn_0.875Fe_0.125I₃, ((CH₃)₂NH₂)Ag_0.5Bi_0.5I₃, and ((NH₂)₂CH)_0.5Rb_0.5SnI₃. These materials, together with others predicted in this study, may be promising candidate materials for stable, highly efficient, and nontoxic perovskite‐based solar cells. 

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