Reversal of the Importance of Steric and Electronic Effects in the Base-Promoted α‑Silylation of Sulfides

Lithiation of α–C-H groups in organic substrates by RLi or R₂NLi followed by silylation with R′₃SiCl generally provides analogous products regardless of the R′ group of R′₃SiCl. A striking exception using 3,4-benzothiophane as substrate depending on whether R′ is methyl, phenyl, or isopropyl is demonstrated. With R′ = Me or Ph, the geminal α,α-bis-silylated products result whereas with <i>i</i>-Pr₃SiCl the <i>trans</i>-α,α′-bis-silylated sulfide is formed. The latter pathway provides ready access to the <i>C</i>₂-symmetric enantiomers of <i>trans</i>-2,5-bis­(triisopropylsilyl)-3,4-benzothiophane

Managing Environmental Research Data.

Environmental science researchers are now using and generating ever-increasing volumes of data and information about our natural world. It is estimated that the Environmental Protection Agency’s (EPA's) STRIVE (Science, Technology, Research and Innovation for the Environment) research funding programme will “involve more than 1,000 researchers and company-based scientists over its seven-year lifetime”1. The EPA's Environmental Research Centre (ERC) expects that large volumes of environmental data and information will be generated by projects funded by STRIVE. One of the key objectives of the STRIVE programme is to make the outcomes and data from this research available “in a coherent and timely manner which will ensure synergies across the wider research agenda and early availability of these outputs into the formulation of policy”2. Consequently, the STRIVE programme must adopt best international practice in environmental research data management. Management of these environmental research data is a core activity for the ERC with particular emphasis on the application of appropriate data management techniques to ensure their long-term availability and accessibility. Environmental research data are often irreplaceable; they are always unique particularly in the spatial location and temporal characteristics of their collection. They can also be extremely expensive and difficult to collect or generate. For these reasons the EPA and the ERC attach great importance to the ongoing development of systems that will ensure that maximum benefits are derived from research data once acquired

High-Dielectric-Permittivity Layered Nitride CaTiN₂

High-Dielectric-Permittivity Layered Nitride CaTiN<sub>2</sub

Metastable γ‑Li₂TiTeO₆: Negative Chemical Pressure Interception and Polymorph Tuning of SHG

Intercepting metastable phases by chemical approaches is an important solution to explore structural varieties of functional materials under positive/negative pressure, as paradigmatically exemplified by the polymorph modification in Li2TiTeO6. Here, we stabilized a novel metastable Li2TiTeO6 (denoted as γ-phase) in the ordered-ilmenite-type R3 via facile topotactic reaction from Na2TiTeO6, which was found to crystallize in R3 instead of the reported R3̅ structure. The calculated equilibrium volume of γ-Li2TiTeO6 is larger than that of the ground-state Pnn2-Li2TiTeO6 (denoted as α-phase), indicating that γ-Li2TiTeO6 can only be stabilized under “negative pressure” quantified to be around −6 GPa. The γ-phase irreversibly transforms into the α-phase around 560 °C under ambient pressure, accompanied by a steep increase (∼500 times) of the second harmonic generation (SHG), indicating a potential application of γ-Li2TiTeO6 as an optical thermometer. These findings elegantly show that chemical pressure as well as physical pressure is powerful to tune the polymorphs for metastable phases and exotic properties as paradigmatically exemplified by Li2TiTeO6, which undergoes consecutive polymorph tuning of γ (−6 GPa), α (0 GPa), β (6 GPa, R3-Ni3TeO6 type), and δ (40 GPa, predicted P21/n double perovskite) phases with densified atomic packing

Metastable γ‑Li₂TiTeO₆: Negative Chemical Pressure Interception and Polymorph Tuning of SHG

Intercepting metastable phases by chemical approaches is an important solution to explore structural varieties of functional materials under positive/negative pressure, as paradigmatically exemplified by the polymorph modification in Li2TiTeO6. Here, we stabilized a novel metastable Li2TiTeO6 (denoted as γ-phase) in the ordered-ilmenite-type R3 via facile topotactic reaction from Na2TiTeO6, which was found to crystallize in R3 instead of the reported R3̅ structure. The calculated equilibrium volume of γ-Li2TiTeO6 is larger than that of the ground-state Pnn2-Li2TiTeO6 (denoted as α-phase), indicating that γ-Li2TiTeO6 can only be stabilized under “negative pressure” quantified to be around −6 GPa. The γ-phase irreversibly transforms into the α-phase around 560 °C under ambient pressure, accompanied by a steep increase (∼500 times) of the second harmonic generation (SHG), indicating a potential application of γ-Li2TiTeO6 as an optical thermometer. These findings elegantly show that chemical pressure as well as physical pressure is powerful to tune the polymorphs for metastable phases and exotic properties as paradigmatically exemplified by Li2TiTeO6, which undergoes consecutive polymorph tuning of γ (−6 GPa), α (0 GPa), β (6 GPa, R3-Ni3TeO6 type), and δ (40 GPa, predicted P21/n double perovskite) phases with densified atomic packing

Metastable γ‑Li₂TiTeO₆: Negative Chemical Pressure Interception and Polymorph Tuning of SHG

Intercepting metastable phases by chemical approaches is an important solution to explore structural varieties of functional materials under positive/negative pressure, as paradigmatically exemplified by the polymorph modification in Li2TiTeO6. Here, we stabilized a novel metastable Li2TiTeO6 (denoted as γ-phase) in the ordered-ilmenite-type R3 via facile topotactic reaction from Na2TiTeO6, which was found to crystallize in R3 instead of the reported R3̅ structure. The calculated equilibrium volume of γ-Li2TiTeO6 is larger than that of the ground-state Pnn2-Li2TiTeO6 (denoted as α-phase), indicating that γ-Li2TiTeO6 can only be stabilized under “negative pressure” quantified to be around −6 GPa. The γ-phase irreversibly transforms into the α-phase around 560 °C under ambient pressure, accompanied by a steep increase (∼500 times) of the second harmonic generation (SHG), indicating a potential application of γ-Li2TiTeO6 as an optical thermometer. These findings elegantly show that chemical pressure as well as physical pressure is powerful to tune the polymorphs for metastable phases and exotic properties as paradigmatically exemplified by Li2TiTeO6, which undergoes consecutive polymorph tuning of γ (−6 GPa), α (0 GPa), β (6 GPa, R3-Ni3TeO6 type), and δ (40 GPa, predicted P21/n double perovskite) phases with densified atomic packing

Novel Fluorinated 8‑Hydroxyquinoline Based Metal Ionophores for Exploring the Metal Hypothesis of Alzheimer’s Disease

Zinc, copper, and iron ions are involved in amyloid-beta (Aβ) deposition and stabilization in Alzheimer’s disease (AD). Consequently, metal binding agents that prevent metal-Aβ interaction and lead to the dissolution of Aβ deposits have become well sought therapeutic and diagnostic targets. However, direct intervention between diseases and metal abnormalities has been challenging and is partially attributed to the lack of a suitable agent to determine and modify metal concentration and distribution <i>in vivo</i>. In the search of metal ionophores, we have identified several promising chemical entities by strategic fluorination of 8-hydroxyquinoline drugs, clioquinol, and PBT2. Compounds <b>15</b>–<b>17</b> and <b>28</b>–<b>30</b> showed exceptional metal ionophore ability (6–40-fold increase of copper uptake and >2-fold increase of zinc uptake) and inhibition of zinc induced Aβ oligomerization (EC₅₀s < ∼5 μM). These compounds are suitable for further development as drug candidates and/or positron emission tomography (PET) biomarkers if radiolabeled with ¹⁸F