Tuning the reduction potential of quinones by controlling the effects of hydrogen bonding, protonation and proton-coupled electron transfer reactions.

An all-organic cell comprising 2,3-dimethyl-1,4-napthoquinone and pyrano[3,2-f]chromene as electroactive elements exhibited a good combination of large cell voltage and stability of the reduced quinone upon the addition of diethyl malonate (a weak organic acid), as compared to the addition of trifluoroethanol (which led to a high cell potential but low stability via strong hydrogen bonding interactions) and the addition of trifluoroacetic acid (which led to a lower cell potential but high stability through proton transfer).

Tetrathiafulvalene aids in the atomic spectroscopic determination of total mercury.

The determination of mercury simultaneously with other elements via inductively coupled plasma-mass spectrometry (ICP-MS) in airborne particulate matter (PM2.5) is still challenging due to the lack of accuracy for the low level mercury concentrations as a result of its volatility and tendency to adhere to the walls of the sample introduction system. This study investigated the effect of existing (gold and methionine) and new (lithium tetrathiafulvalene carboxylate (LiCTTF)) preservation agents in order to improve the determination of trace mercury in PM2.5 samples. Statistical analysis revealed that a concentration of 10 µg mL-1 of LiCTTF was sufficient to obtain highly accurate results with t values of 0.1044-1.1239 which are considerably less than the critical t value of 1.8 and apparent recoveries of 85-100%. An evaluation of the method revealed a spiked mercury recovery of 91% and a detection limit of 0.05 ng mL-1. The method was tested for the determination of trace metals in PM2.5 from atmospheric samples and led to the detection of low elemental concentrations in Singapore's atmosphere. The mechanism for the interaction of mercury with LiCTTF and tetrathiafulvalene (TTF) was studied by conducting in situ electrochemical studies. Cyclic voltammetry and square-wave voltammetry analyses of mercury, and mercury in presence of LiCTTF and TTF revealed complexation between the metal and sulfur-containing compounds.

Sulfoxidation of alkenes and alkynes with NFSI as a radical initiator and selective oxidant.

Sulfoxides are important functional molecules. We develop a short-route (one-pot) synthesis of this class of molecules by reacting thiols with alkenes or alkynes under mild and metal-free conditions. N-Fluorobenzenesulfonimide (NFSI) is used to play dual roles: as a radical initiator for a thiol-ene/-yne reaction to form sulfide adducts, and as efficient oxidant for conversion of the sulfides formed in situ to sulfoxides. Over-oxidation of the sulfoxides to sulfones is avoided in our approach.

Primary-Colored Electrochromism of 1,4-Phenylenediamines.

Ten 1,4-phenylenediamines were studied using electrochemical techniques (voltammetry and controlled potential electrolysis) and UV/Vis spectroscopy under ambient conditions. All compounds demonstrated vibrant color changes upon one-electron electrochemical oxidation in acetonitrile, with most displaying a primary color (red, green, blue, or yellow) in their oxidized state. The four electrochromes that exhibited the most intense color changes were examined by using a gold micromesh electrode laminated inside a polymer film to determine their electrochromic properties in solution (contrast ratios, chromatic efficiency, and cycle life). Their colored radical cations were also characterized by electron paramagnetic resonance spectroscopy as well as monitored for color retention over a period of 24 hours. Notably, only relatively small potentials were required to initiate the chromatic changes and the oxidized forms of the compounds were long-lived and unaffected by atmospheric oxygen or moisture.