Radical-Cation Vinylcyclopropane Rearrangements by TiO Photocatalysis.

Radical cation vinylcyclopropane rearrangements by TiO photocatalysis in lithium perchlorate/nitromethane solution are described. The reactions are triggered by oxidative single electron transfer, which is followed by immediate ring-opening of the cyclopropanes to generate distonic radical cations as unique reactive intermediates. This approach can also be applied to vinylcyclobutane, leading to the construction of six-membered rings.

Probing Intramolecular Electron Transfer in Redox Tag Processes.

Herein, we show that redox tag-guided intermolecular formal [2 + 2] cycloaddition can be used as a probe to investigate intramolecular single-electron transfer (SET) mechanisms. The efficacy of intramolecular SET can be evaluated in association with concomitant carbon-carbon bond formation and/or cleavage, leading to cycloaddition or cross-metathesis. Experimental and theoretical results suggest that the intramolecular SET is under both thermodynamic and kinetic control and can also occur through bonds, not only through space.

Radical Cation Diels-Alder Reactions by TiO Photocatalysis.

Radical cation Diels-Alder reactions by titanium dioxide (TiO) photocatalysis in lithium perchlorate/nitromethane solution are described. TiO photocatalysis promotes reactions between electron-rich dienes and dienophiles, which would otherwise be difficult to accomplish due to electronic mismatching. The reactions are triggered by hole oxidation of the dienophile and are completed by the excited electron reduction of the radical cation intermediate at the dispersed surface in the absence of any sacrificial substrate.

Direct Monitoring of Molecular Events at the Surface: One-Step Access to Flexibly Stable Colloidal Ag Nanoparticles.

Design, control, and direct characterization of surface properties are prerequisites to all the practical applications of nanoparticles. Since stable and homogeneous colloidal conditions are required for most applications, the amenability of nanoparticles to in-solution processing must also be addressed. Herein, we demonstrate that solution H NMR spectroscopy is an effective tool for direct monitoring of the production of Ag nanoparticles.

TiO Photocatalysis in Aromatic "Redox Tag"-Guided Intermolecular Formal [2 + 2] Cycloadditions.

Since the pioneering work by Macmillan, Yoon, and Stephenson, homogeneous photoredox catalysis has occupied a central place in new reaction development in the field of organic chemistry. While heterogeneous semiconductor photocatalysis has also been studied extensively, it has generally been recognized as a redox option in inorganic chemistry where such "photocatalysis" is most often used to catalyze carbon-carbon bond cleavage and not in organic chemistry where bond formation is usually the focal point. Herein, we demonstrate that titanium dioxide photocatalysis is a powerful redox option to construct carbon-carbon bonds by using intermolecular formal [2 + 2] cycloadditions as models.

Understanding the Colloidal Stability of Nanoparticle-Ligand Complexes: Design, Synthesis, and Structure-Function Relationship Studies of Amphiphilic Small-Molecule Ligands.

For effective application of nanoparticles, their amenability to in-solution processing must be addressed, and stable, homogeneous solvent conditions are required. Although organic ligands have been used as surface-modifying reagents for nanoparticles to increase their colloidal stability and homogeneity in solution, the structure-function relationships of nanoparticle-ligand complexes remain elusive and controversial. Herein, a series of novel amphiphilic small-molecule ligands were designed, synthesized, and applied as surface-modifying reagents for aqueous, transparent TiO and ZrO nanoparticles.