Synthesis of Structurally Well‐Defined Telechelic Polymers by Organostibine‐Mediated Living Radical Polymerization: In Situ Generation of Functionalized Chain‐Transfer Agents and Selective ω‐End‐Group Transformations

Several organostibine chain‐transfer agents possessing polar functional groups have been prepared by the reactions of azo initiators and tetramethyldistibine ( 1 ). Carbon‐centered radicals thermally generated from the azo initiators were trapped by 1 to yield the corresponding organostibine chain‐transfer agents. The high yields observed in the synthesis of the chain‐transfer agents strongly suggest that distibines have excellent radicophilic reactivity. As the reactions proceeded under neutral conditions, functional groups that are incompatible with ionic conditions were incorporated into the chain‐transfer agents. The chain‐transfer agents were used in living radical polymerization to synthesize the corresponding α‐functionalized polymers. As the functional groups in the chain‐transfer agents did not interfere with the polymerization reaction, well‐controlled polymers possessing number‐average molecular weights (M_ns) predetermined by the monomer/transfer agent ratios were synthesized with low polydispersity indices (PDIs). The organostibanyl ω‐polymer ends were transformed into a number of different functional groups by radical‐coupling, radical‐addition, and oxidation reactions. Therefore, it was possible to synthesize well‐controlled telechelic polymers with the same and also with different functional groups at their α‐ and ω‐polymer ends. Distibine 1 was also found to increase PDI control in the living radical polymerization of styrene and methyl methacrylate (MMA) using a purified organostibine chain‐transfer agent. Well‐controlled poly(methyl methacrylate)s with M_n values ranging from 10 000 to 120 000 with low PDIs (1.05–1.15) were synthesized by the addition of a catalytic amount of 1 . The results have been attributed to the high reactivity of distibine 1 towards polymer‐end radicals, which are spontaneously deactivated to yield organostibine dormant species.     

Flameless Atomic Absorption Determination of Volatile Hydrides Using Cold Trap Collection

Abstract

The hydrides of arsenic, antimony, bismuth, and selenium are collected in a liquid nitrogen cold trap and then volatilized into either an argon-entrained air-hydrogen flame or into a Perkin-Elmer HGA-2000 Graphite Furnace for atomic absorption measurement. Flameless atomization results in approximately ten-fold lower detection limits. The sensitivities and detection limits in nanograms are, respectively, 1.0 and 0.2 for arsenic, 5.6 and 1 for antimony, 2.0 and 1 for bismuth, and 40 and 10 for selenium.     

The Rb7Bi3−3xSb3xCl16 Family: A Fully Inorganic Solid Solution with Room‐Temperature Luminescent Members

Low‐dimensional ns²‐metal halide compounds have received immense attention for applications in solid‐state lighting, optical thermometry and thermography, and scintillation. However, these are based primarily on the combination of organic cations with toxic Pb²⁺ or unstable Sn²⁺, and a stable inorganic luminescent material has yet to be found. Here, the zero‐dimensional Rb₇Sb₃Cl₁₆ phase, comprised of isolated [SbCl₆]^3? octahedra and edge‐sharing [Sb₂Cl₁₀]^4? dimers, shows room‐temperature photoluminescence (RT PL) centered at 560 nm with a quantum yield of 3.8±0.2 % at 296 K (99.4 % at 77 K). The temperature‐dependent PL lifetime rivals that of previous low‐dimensional materials with a specific temperature sensitivity above 0.06 K^?1 at RT, making it an excellent thermometric material. Utilizing both DFT and chemical substitution with Bi³⁺ in the Rb₇Bi_3?3xSb_3xCl₁₆ (x≤1) family, we present the edge‐shared [Sb₂Cl₁₀]^4? dimer as a design principle for Sb‐based luminescent materials.     

Metal‐Free Stabilization of Monomeric Antimony(I): A Carbene‐Supported Stibinidene

A diamidocarbene was coordinated to an antimony(III) dichloride Lewis acid. Subsequent reduction with magnesium gave a monomeric, formally antimony(I) fragment that is supported by the diamidocarbene. Spectroscopic, crystallographic, and computational analyses demonstrated that the carbene ligand engages the antimony(I) center in π‐backbonding resulting in a short (2.068(7) Å) Sb?C interaction that is comparable to those observed in known stibaalkenes.     

Air Gap Microcell for Scanning Electrochemical Microscopic Imaging of Carbon Dioxide Output. Model Calculation and Gas Phase SECM Measurements for Estimation of Carbon Dioxide Producing Activity of Microbial Sources

Most of SECM studies have been carried out in liquid or gel phases. A Severinghaus type, CO₂ detecting potentiometric tip has been fabricated and used in gas phase SECM studies. The microcell tip is made without gas permeable membrane. Faster response, needed in SECM, was achieved by substituting the membrane with an air gap. The carbon dioxide concentration profile in the gas phase over a disc‐shaped colony of yeast has been detected with the new tip. Estimation of the carbon dioxide output of the fungi colony was attempted by fitting simulated curves to measured ones obtained with one dimensional (line) scans.     

Synthesis of a Molecule with Four Different Adjacent Pnictogens

The synthesis of a molecule containing four adjacent different pnictogens was attempted by conversion of a Group 15 allyl analogue anion [Mes*NAsPMes*]^? (Mes*=2,4,6‐tri‐tert‐butylphenyl) with antimony(III) chloride. A suitable precursor is Mes*N(H)AsPMes* ( 1 ) for which several syntheses were investigated. The anions afforded by deprotonation of Mes*N(H)AsPMes* were found to be labile and, therefore, salts could not be isolated. However, the in situ generated anions could be quenched with SbCl₃, yielding Mes*N(SbCl₂)AsPMes* ( 4 ).     

Synthesis of Six-Membered Functionalized Carbocyclic Compounds by One-Pot Reaction of Hydroquinone Derivatives and Dienes

A general method for one-pot reaction of hydroquinone derivatives and dienes has been developed. The system of Pb₃O₄ in tetrahydrofuran–trifluoroacetic acid was found to play dual roles as oxidant for the generation of quinones in situ and as catalyst for the Diels–Alder cycloaddition, which makes the one-pot reaction efficient and easy to carry out. Using this method, a variety of six-membered functionalized carbocyclic compounds can be easily prepared in medium to excellent yields at room temperature.