Metal-containing triarylboron compounds for optoelectronic applications

Triarylboranes have recently emerged as a powerful new class of electron acceptors with great potential as optoelectronic materials. The empty p(z) orbital on the boron centre promotes strong charge-transfer transitions, leading to highly luminescent compounds with colors spanning the entire visible spectrum. Due to intense research efforts over the past decade, many examples now exist of organic molecules based on this structural motif. Only recently, however, have transition metal-containing triarylboranes been closely investigated. These compounds are capable of bright luminescence from a triplet excited state, and have been developed as efficient emissive materials for organic light-emitting diodes (OLEDs) as a result. In addition, their long-lived phosphorescence gives these materials potential as highly selective chemical sensors for small anions using time-gated detection, eliminating interference from background fluorescence. The research of the past several years has now led to a better understanding of the impact of the triarylboron group on the photophysical properties of metal complexes, which we expect will provide many opportunities for research into this class of functional phosphorescent materials.     

Fe3O4 nanoparticle-supported copper(I) pybox catalyst: magnetically recoverable catalyst for enantioselective direct-addition of terminal alkynes to imines

An Fe(3)O(4) nanoparticle-supported copper(I) pybox catalyst, which exhibits excellent reactivity and yields products with good enantioselectivity, was developed. As a proof of concept, six optically active propargyl amines were obtained in excellent yields. The catalyst can be magnetically removed and recycled easily six times without a decrease in activity or enantioselectivity.     

Occupied and Unoccupied Orbitals of C60 and C70

Abstract

The full spectrum of occupied and unoccupied σ and π orbitals is presented for solid C₆₀, C₇₀, and graphite, using Cls emission and absorption spectroscopy. There are significant diffcrences between C₆₀ and C₇₀, and even larger changes relative to their infinite analog graphite (C∝). A comparison is made with photocmission and inverse photoemission results, along with first principles quasiparticle calculations.     

Classification of chromatographic data using multidimensional polynomials

Summary A pattern recognition methodology has been developed for analysis of chromatographic data. The method uses a new class of multidimensional orthogonal polynomials developed by Cohen in conjunction with a supervised learning technique. The method is applicable to any chromatographic data for which classification into two or more categories is desired. The algorithm analyzes both elution times and peak areas. An application is shown for the analysis of organic acids in ascitic fluid obtained from patients with liver disorders. Classification of these patients for presence or absence of bacterial infection shows over ninety percent correct classification.     

[Sm(NO3)3(TPTZ)(H2O)]·2H2O [TPTZ is 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine]

The title compound, aqua­tris­(nitrato)[2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine]samarium dihydrate, [Sm(NO₃)₃­(C₁₈H₁₂N₆)­(H₂O)]·­2H₂O, was prepared from Sm(NO₃)₃·6H₂O and 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine. The metal atom is ten‐coordinate being bonded to the terdentate TPTZ ligand, three bidentate nitrates and a water mol­ecule.     

Iron-iron oxide core-shell nanoparticles are active and magnetically recyclable olefin and alkyne hydrogenation catalysts in protic and aqueous media

We report for the first time the use of iron-iron oxide core-shell nanoparticles for the hydrogenation of olefins and alkynes under mild conditions in ethanol and in an aqueous medium. This catalyst proves robust towards the presence of oxidants, such as oxygen and water, is magnetically recoverable and shows selectivity towards the less activated double bonds.     

THE PREPARATION OF TRIALKYL PHOSPHITES DIRECTLY FROM THE ELEMENT

Abstract

The reaction between finely divided white phosphorus and several alkoxide ions in the presence of tetrachloromethane and excess of alcohol has been investigated under a variety of conditions. High yields of trialkylphosphite are obtained when two equivalents of alkoxide are used. With one equivalent of alkoxide, dialkylphosphonate is formed in comparable yield. Maximum yields of triester are obtained within 1–3 h at room temperature. Prolonged treatment results in the conversion of trialkylphosphite to phosphate by reaction with tetrachloromethane. Phenolate ions are unreactive under the same experimental conditions. The mechanism of the reaction is discussed.     

Mode-locked fiber laser frequency-controlled with an intracavity electro-optic modulator

We demonstrate a mode-locked, erbium-doped fiber laser with its repetition frequency synchronized to a second fiber laser via an intracavity electro-optic modulator (EOM). With servo control from the EOM (bandwidth approximately 230 kHz) and a slower speed intracavity piezoelectric transducer (resonance at approximately 20 kHz), we demonstrate stabilization of the repetition frequency with an in-loop rms timing jitter of 10 fs, integrated over a bandwidth from 1 Hz to 100 kHz. This represents what is to our knowledge the first time an EOM has been introduced inside a mode-locked laser cavity for fast servo action and the lowest timing jitter reported for a mode-locked fiber laser.     

Unconventional, highly selective CO2 adsorption in zeolite SSZ-13

Low-pressure adsorption of carbon dioxide and nitrogen was studied in both acidic and copper-exchanged forms of SSZ-13, a zeolite containing an 8-ring window. Under ideal conditions for industrial separations of CO(2) from N(2), the ideal adsorbed solution theory selectivity is >70 in each compound. For low gas coverage, the isosteric heat of adsorption for CO(2) was found to be 33.1 and 34.0 kJ/mol for Cu- and H-SSZ-13, respectively. From in situ neutron powder diffraction measurements, we ascribe the CO(2) over N(2) selectivity to differences in binding sites for the two gases, where the primary CO(2) binding site is located in the center of the 8-membered-ring pore window. This CO(2) binding mode, which has important implications for use of zeolites in separations, has not been observed before and is rationalized and discussed relative to the high selectivity for CO(2) over N(2) in SSZ-13 and other zeolites containing 8-ring windows.