Role of Electronic Structure in the Martensitic Phase Transition of Ni_2Mn_<1-x>Sn_<1-x> Studied by Hard-X-Ray Photoelectron Spectroscopy and Ab Initio Calculation

We have revealed the underlying mechanism of the martensitic phase transition (MPT) in a new class of ferromagnetic shape memory alloys, Ni2Mn1+xSn1-x, by the combination of bulk-sensitive hard-x-ray photoelectron spectroscopy and a first-principles density-functional calculation. The Ni 3d eg state in the cubic phase systematically shifts towards the Fermi energy with an increase in the number of Mn atoms substituted in the Sn sites. An abrupt decrease of the intensity of the Ni 3d eg states upon MPT for x=0.36–0.42 has been observed in the vicinity of the Fermi level. The energy shift of the Ni 3d minority-spin eg state in the cubic phase originates from hybridization with the antiferromagnetically coupled Mn in the Sn site. Below the MPT temperature, the Ni 3d state splits into two levels located below and above the Fermi energy in order to achieve an energetically stable state

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Direct Dimesitylborylation of Benzofuran Derivatives by an Iridium-Catalyzed C-H Activation with Silyldimesitylborane

Direct dimesitylborylation of benzofuran derivatives by a C-H activation catalyzed by an iridium(I)/N-heterocyclic carbene (NHC) complex in the presence of Ph2MeSi-BMes(2) afforded the corresponding dimesitylborylation products in good to high yield with excellent regioselectivity. This method provides a straightforward route to donor-(pi-spacer)-acceptor systems with intriguing solvatochromic luminescence properties

General Synthesis of Trialkyl- and Dialkylarylsilylboranes: Versatile Silicon Nucleophiles in Organic Synthesis

Compared to carbon-based nucleophiles, the number of silicon-based nucleophiles that is currently available remains limited, which significantly hampers the structural diversity of synthetically accessible silicon-based molecules. Given the high synthetic utility and ease of handling of carbon-based boron nucleophiles, silicon-based boron nucleophiles, i.e., silylboranes, have attracted considerable interest in recent years as nucleophilic silylation reagents that are activated by transition-metal catalysts or bases. However, the range of practically accessible silylboranes remains limited. In particular, the preparation of sterically hindered and functionalized silylboranes remains a significant challenge. Here, we report the use of rhodium and platinum catalysts for the direct borylation of hydrosilanes with bis(pinacolato)diboron, which allows the synthesis of new trialkylsilylboranes that bear bulky alkyl groups and functional groups as well as new dialkylarylsilylboranes that are difficult to synthesize via conventional methods using alkali metals. We further demonstrate that these compounds can be used as silicon nucleophiles in organic transformations, which significantly expands the scope of synthetically accessible organosilicon compounds compared to previously reported methods. Thus, the present study can be expected to inspire the development of efficient methods for novel silicon-containing bioactive molecules and organic materials with desirable properties. We also report the first B-11{H-1} and Si-29(H-1) NMR spectroscopic evidence for the formation of i-Pr3SiLi generated by the reaction of i-Pr3Si-B(pin) with MeLi

Synthesis of hydrosilylboronates via the monoborylation of a dihydrosilane Si-H bond and their application for the generation of dialkylhydrosilyl anions

The synthesis of a series of hydrosilylboronates via the selective iridium- or nickel-catalyzed monoborylation of dihydrosilane Si-H bonds is described. The synthesized silylboronates, which bear a single Si-H bond, can be used as novel silicon nucleophiles in the presence of transition-metal catalysts or bases. The first Si-29{H-1} NMR spectroscopic evidence for the formation of (t-Bu)(2)HSiLi, generated by the reaction of (t-Bu)(2)HSi-B(pin) with MeLi, is reported as the first example of a dialkylhydorosilyl lithium species

Tris(trimethylsilyl)silylboronate Esters: Novel Bulky, Air- and Moisture-Stable Silylboronate Ester Reagents for Boryl Substitution and Silaboration Reactions

New, bulky tris­(trimethylsilyl)­silylboronate pinacol and hexylene glycol esters ((TMS)₃Si–B­(pin) and (TMS)₃Si–B­(hg)) were prepared in 46 and 61% yields, respectively, by the reaction of tris­(trimethylsilyl)­silylpotassium with the corresponding boron electrophiles. Notably, these silylboronate esters exhibited high stability to air and silica gel and were applied to the transition-metal-free boryl substitution of aryl halides, providing the desired borylated products in high yields with excellent B:Si ratios (up to 96% yield, B/Si = 99/1). These new silylboronate esters were also applied to a sequential borylation/cross-coupling process with various aryl halides, as well as the base-mediated silaboration of styrene

General Synthesis of Trialkyl- and Dialkylarylsilylboranes: Versatile Silicon Nucleophiles in Organic Synthesis

Compared to carbon-based nucleophiles, the number of silicon-based nucleophiles that is currently available remains limited, which significantly hampers the structural diversity of synthetically accessible silicon-based molecules. Given the high synthetic utility and ease of handling of carbon-based boron nucleophiles, silicon-based boron nucleophiles, i.e., silylboranes, have attracted considerable interest in recent years as nucleophilic silylation reagents that are activated by transition-metal catalysts or bases. However, the range of practically accessible silylboranes remains limited. In particular, the preparation of sterically hindered and functionalized silylboranes remains a significant challenge. Here, we report the use of rhodium and platinum catalysts for the direct borylation of hydrosilanes with bis(pinacolato)diboron, which allows the synthesis of new trialkylsilylboranes that bear bulky alkyl groups and functional groups as well as new dialkylarylsilylboranes that are difficult to synthesize via conventional methods using alkali metals. We further demonstrate that these compounds can be used as silicon nucleophiles in organic transformations, which significantly expands the scope of synthetically accessible organosilicon compounds compared to previously reported methods. Thus, the present study can be expected to inspire the development of efficient methods for novel silicon-containing bioactive molecules and organic materials with desirable properties. We also report the first B-11{H-1} and Si-29(H-1) NMR spectroscopic evidence for the formation of i-Pr3SiLi generated by the reaction of i-Pr3Si-B(pin) with MeLi