Rigaku (United States)

These studies reveal the first structure of Clostridiumacetobutylicum alcohol dehydrogenase (CaADH), a protein exhibiting remarkable substrate promiscuity and stereochemical fidelity. The CaADH enzyme is utilized here for synthesizing 20 potential aryl isoserine side chains for the Taxotère family of tubulin‐binding chemotherapeutics. The approach involves dynamic reductive kinetic resolution (DYRKR) upon the corresponding α‐chloro‐β‐keto esters, showing high D‐syn stereoselectivity, including those leading to the clinically relevant Milataxel (Ar = 2‐furyl) and Simotaxel (Ar = 2‐thienyl) side chains. Furthermore, various cross‐coupling chemistries performed on the p‐bromophenyl isoserine side chain significantly enhance the structural diversity of the taxoid side chain library obtained (16 additional taxoid side chains). The CaADH structure is notable: (i) the nicotinamide cofactor is bound in an anti‐conformation, with the amide carbonyl occupying the ketone binding pocket, and (ii) a flexible loop near the active site, likely contributes to the remarkable substrate promiscuity observed in CaADH. We present our perspective on the dynamic nature of the CaADH active site through molecular dynamics simulation, proposing a halogen bonding model as a potential mechanism for the remarkable selectivity for an (S)‐configured C‐Cl bond, in addition to the D‐facial selectivity, demonstrated across twenty diverse substrates by this remarkable short‐chain dehydrogenase enzyme.

Since its launch in 2021, the XtaLAB Synergy-ED has produced many structures, with over 500 unique structures from Rigaku labs alone. CrysAlisPro implements all essential workflows for screening, data collection and data reduction. Recent developments focused on making electron diffraction as easy as X-ray diffraction, allowing novice users to transition from X-ray workflows swiftly. The update will focus on the crystallographic user perspective in operating our JEOL/Rigaku electron diffractometer: The advanced GUI simplifies the interaction with the electron optics for detector distance, beam strength, ultra-low dose operation (flash mode) and easy transition between visual and diffraction modes.The data collection separates screening and complete collection operations with tuneable concurrent analysis.The automation by queue operation now offers automatic z-centring to further reduce the interactive operation of the instrument.Data reduction now includes expanded export for dynamic refinement with Jana2020 and Olex2 AutoChem.Merging tools are improved and can be used with external cluster analysis tools.The results viewer is expanded to handle multi-grain workflows.Simple instrument calibration. Furthermore, the essentials of operating AutoChem Olex2 with kinematical and dynamical data will be highlighted.

Advanced semiconductor devices are moving toward three-dimensional (3D) geometries due to scaling demands and performance requirements. Non-destructive metrology necessary for process control of 3D structures must be advanced to facilitate their transition from technology development to high-volume manufacturing. Thin film metrology using Mueller matrix spectroscopic ellipsometry (MMSE) and X-ray diffraction (XRD) film metrology, as well as patterned structure metrology using optical critical dimension (OCD) and X-ray fluorescence (XRF) techniques, have proved capable of measuring the Si∕Si 1−x Ge x superlattices and gate-all-around transistor test structures. Because these techniques are indirect, their limitations associated with superlattice device structures need to be further understood. To understand these limitations, a four-superlattice layer Si∕Si 1−x Ge x structure was measured at four process steps: as an unpatterned film stack, after anisotropic column etch, and at low and high levels of cavity etch. Thin film samples were analyzed with XRD and MMSE, and patterned samples were analyzed using OCD, as well as XRF. A model was developed describing the primary and secondary process effects on the structure. This was evaluated for consistency on datasets collected at different measurement azimuth angles. Square error-based methods were evaluated to quantify OCD model detectability of fit variable step deviations, as well as sensitivity relative to the model to measurement error. OCD and XRF results were compared with reference scanning transmission electron microscopy (STEM) images of nanowire test structure lamellae. Dual-azimuth fit OCD models were found to be within 0.3 nm of the STEM reference mean.

Selective coupling of NO by a nonclassical dinuclear dinitrosyliron complex (D-DNIC) to form N2O is reported. The coupling is facilitated by the pyridinediimine (PDI) ligand scaffold, which enables the necessary denticity changes to produce mixed-valent, electron-deficient tethered DNICs. One-electron oxidation of the [{Fe(NO)2}]210/10 complex Fe2(PyrrPDI)(NO)4 (4) results in NO coupling to form N2O via the mixed-valent {[Fe(NO)2]2}9/10 species, which possesses an electron-deficient four-coordinate {Fe(NO)2}10 site, crucial in N-N bond formation. The hemilability of the PDI scaffold dictates the selectivity in N-N bond formation because stabilization of the five-coordinate {Fe(NO)2}9 site in the mixed-valent [{Fe(NO)2}]29/10 species, [Fe2(Pyr2PDI)(NO)4][PF6] (6), does not result in an electron-deficient, four-coordinate {Fe(NO)2}10 site, and hence no N-N coupling is observed.

3D electron diffraction (3D ED)/Micro electron diffraction (MicroED) has extended the limits of crystallography by enabling the determination of three dimensional molecular structures from sub-μm microcrystals. However, 3D ED/microED measurements using current state-of-the-art electron microscopes require experts in both electron microscopy and crystallography making the method rather difficult for researchers who simply need structures. Here, we present a diffractometer specifically designed for 3D ED/microED and show how it works for determining crystal structures. The newly developed electron diffractometer will provide many researchers with an easy path to structure determination of crystals that are less than 1 μm in size.

Self-assembled complexesutilizing the ditopic dative bond acceptor1,3-diboronic acid with catechol and complementary U-shaped donorsin the form of 1,8-dipyridylnaphthalenes (1,8-bis(4-pyridyl)naphthalene(DPN), 1,8-bis(4-ethylenylpyridyl)naphthalene (DEPN), and 1,8-bis(4-ethynylpyridyl)naphthalene (DAPN)) yielded discrete two-component structures. The assemblies exhibit“plug-in-socket” geometries. DFT calculations are consistentwith the donor pyridyl and acceptor catecholate being electron poorand rich, respectively. The assemblies pack via π–πinteractions and support the inclusion of a solvent (i.e., DPN, DAPN). The materials may form a basis for the designof complex B-based structures (e.g., supramolecular dyads).

The atomic-level tunability of molecular structures is a compelling reason to develop homogeneous catalysts for challenging reactions such as the electrochemical reduction of carbon dioxide to valuable C1-Cn products. Of particular interest is methane, the largest component of natural gas. Herein, we report a series of three isomeric rhenium tricarbonyl complexes coordinated by the asymmetric diimine ligands 2-(isoquinolin-1-yl)-4,5-dihydrooxazole (quin-1-oxa), 2-(quinolin-2-yl)-4,5-dihydrooxazole (quin-2-oxa), and 2-(isoquinolin-3-yl)-4,5-dihydrooxazole (quin-3-oxa) that catalyze the reduction of CO2 to carbon monoxide and methane, albeit the latter with a low efficiency. To our knowledge, these complexes are the first examples of rhenium(I) catalysts capable of converting carbon dioxide into methane. Re(quin-1-oxa)(CO)3Cl (1), Re(quin-2-oxa)(CO)3Cl (2), and Re(quin-3-oxa)(CO)3Cl (3) were characterized and studied using a variety of electrochemical and spectroscopic techniques. In bulk electrolysis experiments, the three complexes reduce CO2 to CO and CH4. When the controlled-potential electrolysis experiments are performed at -2.5 V (vs Fc+/0) and in the presence of the Brønsted acid 2,2,2-trifluoroethanol, methane is produced with turnover numbers that range from 1.3 to 1.8. Isotope labeling experiments using 13CO2 atmosphere produce 13CH4 (m/z = 17) confirming that methane originates from CO2 reduction. Theoretical calculations are performed to investigate the mechanistic aspects of the 8e-/8H+ reduction of CO2 to CH4. A ligand-assisted pathway is proposed to be an efficient pathway in the formation of CH4. Delocalization of the electron density on the (iso)quinoline moiety upon reduction stabilizes the key carbonyl intermediate leading to additional reactivity of this ligand. These results should aid the development of more robust catalytic systems that produce CH4 from CO2.

Metal oxo clusters and metal oxides assemble and precipitate from water in processes that depend on pH, temperature, and concentration. Other parameters that influence the structure, composition, and nuclearity of "molecular" and bulk metal oxides are poorly understood, and have thus not been exploited. Herein, we show that Bi3+ drives the formation of aqueous Fe3+ clusters, usurping the role of pH. We isolated and structurally characterized a Bi/Fe cluster, Fe3 BiO2 (CCl3 COO)8 (THF)(H2 O)2 , and demonstrated its conversion into an iron Keggin ion capped by six Bi3+ irons (Bi6 Fe13 ). The reaction pathway was documented by X-ray scattering and mass spectrometry. Opposing the expected trend, increased cluster nuclearity required a pH decrease instead of a pH increase. We attribute this anomalous behavior of Bi/Fe(aq) solutions to Bi3+ , which drives hydrolysis and condensation. Likewise, Bi3+ stabilizes metal oxo clusters and metal oxides in strongly acidic conditions, which is important in applications such as water oxidation for energy storage.

Small angle X-ray scattering (SAXS) is a useful technique for extracting structural information from biological samples in solution. However, the X-ray scattering signal from macromolecules is challenging to measure because of low particle concentrations and high background from solvent. As a result, instrument designs for home laboratories, where X-ray intensities are lower than synchrotrons, require special scrutiny. In particular, collimation design, X-ray source and area detector contribute greatly to improved data quality for home laboratory experiments.