Rational Synthesis of Metallo-Cations Toward Redox- and Alkaline-Stable Metallo-Polyelectrolytes.

Cations are crucial components in emerging functional polyelectrolytes for a myriad of applications. Rapid development in this area necessitates the exploration of new cations with advanced properties. Herein we describe a combination of computational and experimental design of cobaltocene metallo-cations that have distinct electronic and redox properties. One of the direct outcomes on the first synthesis of a complete set of cation derivatives is to discover highly stable cations, which are further integrated to construct metallo-polyelectrolytes as anion-exchange membranes in solid-state alkaline fuel cells. The device performance of these polyelectrolytes under highly basic and oxidative environments is competitive with many organo-polyelectrolytes.

UV-irradiation of self-assembled triphenylamines affords persistent and regenerable radicals.

UV-irradiation of assembled urea-tethered triphenylamine dimers results in the formation of persistent radicals, whereas radicals generated in solution are reactive and quickly degrade. In the solid-state, high quantities of radicals (approximately 1 in 150 molecules) are formed with a half-life of one week with no significant change in the single crystal X-ray diffraction. Remarkably, after decay, re-irradiation of the solid sample regenerates the radicals to their original concentration. The photophysics upon radical generation are also altered. Both the absorption and emission are significantly quenched without external oxidation likely due to the delocalization of the radicals within the crystals. The factors that influence radical stability and generation are correlated to the rigid supramolecular framework formed by the urea tether of the triphenylamine dimer. Electrochemical evidence demonstrates that these compounds can be oxidized in solution at 1.0 V vs. SCE to generate radical cations, whose EPR spectra were compared with spectra of the solid-state photogenerated radicals. Additionally, these compounds display changes in emission due to solvent effects from fluorescence to phosphorescence. Understanding how solid-state assembly alters the photophysical properties of triphenylamines could lead to further applications of these compounds for magnetic and conductive materials.

Selective N1-Acylation of Indazoles with Acid Anhydrides Using an Electrochemical Approach.

An electrochemical synthesis method for the selective N1-acylation of indazoles has been developed. This "anion pool" approach electrochemically reduces indazole molecules generating indazole anions and H2. Acid anhydrides are then introduced to the solution resulting in selective acylation of the N1-position of the indazoles. This procedure can also be applied to the acylation of benzimidazoles and indoles. The reaction can also be performed using a 9 V battery without loss of reaction efficiency.