Amperometric detection of amines and amino acids in flow injection systems with a nickel oxide electrode

The use and characteristics of a nickel oxide electrode as a detector for amines in a flow injection system are described. The anodic electrode reaction mechanism involves a higher oxidation state of nickel maintained by the applied potential (+0.49 V vs. SCE). The electroanalytical parameters are investigated and the currents for a series of amines and amino acids are compared. Two electrode configurations are compared. The flow injection technique is shown to be suitable for buffered 25-μl samples of pH as low as 3. The linear range for glycine is 10^-6–10^-3 M with detection limits of a few nanograms.     

Optical absorption of the β‐phase of poly(9,9‐dioctylfluorene)

We outline a theory for the optical absorption of the β‐phase of poly(9,9‐dioctylfluorene) (PFO) that is based on the Frenkel exciton model. The absorption peak at 435 nm is attributed to polymer segments having torsion angles equal to π that are weakly perturbed by the presence of random monomer junctions with torsion angles equal to 0. The broad band below 435 nm is associated with disordered segments having a broad distribution of random torsion angles. The effects of small random deviations from π in the torsion angles are discussed. The calculations support the interpretation that the β‐phase is characterized by alternating segments of highly ordered and strongly disordered regions. PFO is a widely studied fluorene‐based polymer with interesting and potentially useful photophysical properties. In this work, Frenkel exciton states in the β‐phase of PFO are studied, and a two‐region model—weak torsional disorder and strong torsional disorder—is presented. The peak in the optical absorption at 435 nm is associated with the weakly disordered regions. The broad background in the absorption is attributed to the strongly disordered regions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1109–1111     

Access to Enantiomerically Pure P-Stereogenic Primary Aminophosphine Sulfides under Reductive Conditions

Stereochemically pure phosphines with phosphorus-heteroatom bonds and P-centered chirality are a promising class of functional building blocks for the design of chiral ligands and organocatalysts. A route to enantiomerically pure primary aminophosphine sulfides was opened through stereospecific reductive C−N bond cleavage of phosphorus(V) precursors by lithium in liquid ammonia. The chemoselectivity of the reaction as a function of reaction time, substrate pattern, and chiral auxiliary was investigated. In the presence of exclusively aliphatic groups bound to the phosphorus atom, all competing reductive side reactions are totally prevented. The absolute configurations of all P-stereogenic compounds were determined by single-crystal X-ray diffraction analysis. Their use as synthetic building blocks was demonstrated. The lithium salt of (R)-BINOL-dithiophosphoric acid proved to be a useful stereochemical probe to determine the enantiomeric purity. Insights into the coordination mode of the lithium-based chiral complex formed in solution was provided by NMR spectroscopy and DFT calculations.