Ir(I)/HCl Catalyzed Head-to-Tail Homocoupling Reactions of Vinylsilanes

Novel homocoupling reactions of vinylsilanes, catalyzed by a mixture of Ir(I) and HCl, were developed. This process leads to exclusive formation of head-to-tail vinylsilane dimers in high yields at room temperature. Synthetic attributes of transformations of the resulting head-to-tail vinylsilane dimers and polymerization of bis(vinylsilane) were investigated

Rhodium-Catalyzed Enantioselective Cycloisomerization to Cyclohexenes Bearing Quaternary Carbon Centers

We report a Rh-catalyzed enantioselective cycloisomerization of α,ω-heptadienes to afford cyclohexenes bearing quaternary carbon centers. Rhodium­(I) and a new SDP ligand promote chemoselective formation of a cyclohex-3-enecarbaldehyde motif that is inaccessible by the Diels–Alder cycloaddition. Various α,α-bisallylaldehydes rearrange to generate six-membered rings by a mechanism triggered by aldehyde C–H bond activation. Mechanistic studies suggest a pathway involving regioselective carbometalation and endocyclic β-hydride elimination

Li₂RuO₃ as an Additive for High-Energy Lithium-Ion Capacitors

A high-energy lithium ion capacitor that has Li₂MoO₃ as an alternative lithium source instead of metallic lithium has been proposed. For further improvement, we suggest Li₂RuO₃ as a new additive to improve the energy density in the positive electrode. The choice of Li₂RuO₃ is made based on its highly reversible characteristics for Li⁺ insertion and extraction and its structural stability in the operating voltage window of advanced lithium ion capacitors. The electrochemical and structural properties of Li₂RuO₃ have been thoroughly investigated to demonstrate its potential use in lithium ion capacitors. The high reversibility of Li₂RuO₃ and the metallic feature of Li_2–<i>x</i>RuO₃ may be responsible for improvements in the volumetric energy density and safety. This versatile approach may yield higher energy density without significant power loss in lithium ion capacitors

Directional Electron Transfer in Chromophore-Labeled Quantum-Sized Au₂₅ Clusters: Au₂₅ as an Electron Donor

Novel Au₂₅(C₆S)₁₇PyS clusters (pyrene-functionalized Au₂₅ clusters) showing interesting electrochemical and optical properties are synthesized and characterized. Significant fluorescence quenching is observed for pyrene attached to Au₂₅ clusters, suggesting strong excited-state interactions. Time-resolved fluorescence upconversion and transient absorption measurements are utilized to understand the excited-state dynamics and possible interfacial electron- and energy-transfer pathways. Electrochemical investigations suggest the possibility of electron transfer from Au₂₅ clusters to the attached pyrene. Fluorescence upconversion measurements have shown faster luminescence decay for the case of pyrene attached to Au₂₅ clusters pointing toward ultrafast photoinduced electron/energy-transfer pathways. Femtosecond transient absorption measurements have revealed the presence of the anion radical of pyrene in the excited-state absorption, suggesting the directional electron transfer from Au₂₅ clusters to pyrene. The rate of forward electron transfer from the Au₂₅ cluster to pyrene is ultrafast (∼580 fs), as observed with femtosecond fluorescence upconversion and transient absorption