This Review deals with the evolving field of polyhalogen chemistry, specifically polyhalogen anions (polyhalides). In addition to a historical outline, current progress in synthetic approaches towards the formation of polyfluorides, polychlorides, polybromides, and polyinterhalides is also illustrated. The structural diversity of polyhalides has substantially increased in the past decade, especially for polychlorides and polybromides, which are commonly characterized by single‐crystal X‐ray diffraction, Raman spectroscopy, and quantum‐chemical calculations. Polyfluorides have been examined by sophisticated state‐of‐the‐art quantum‐chemical calculations and investigated spectroscopically in noble gas matrix‐isolation experiments under cryogenic conditions at 4 K. The bonding in such polyhalide systems is also discussed. The last Section deals with applications of polyhalides in halogenation reactions and electrochemistry as well as their use as reactive ionic liquids, emphasizing the promising future of polyhalogen chemistry.
Simultaneous elemental detection of F and Cl offers quantitation of fluorinated and chlorinated compounds and their transformation products without compound-specific standards. Despite wide-ranging applications, this capability has been hindered by fundamental and technical shortcomings of current inductively coupled plasma (ICP)-MS methods in ion formation and isobaric interference elimination. These hurdles are alleviated here via a chemical ionization method. Fluorine and chlorine in analytes are first converted to HF and HCl by an ICP with post-plasma recombination and subsequently react with barium-containing ions supplied by a nanospray, yielding BaF + and BaCl + as elemental reporter ions. Notably, the method is readily interfaced to an Orbitrap MS which eliminates isobaric interferences at resolving powers as low as 35,000, far greater than that of current ICP−MS instruments. Moreover, the instrument is easily reverted to the ESI-MS mode for complementary molecular characterization. To demonstrate analytical capabilities, a workflow for rapid quantitation of compounds separated by reversed-phase liquid chromatography is developed using a species-independent calibration. The independent F and Cl measurements agree with each other, providing recoveries of >90% and LODs of 8−12 pmol Cl and 5− 12 pmol F on the column. The workflow along with LC-ESI-MS on the same instrument is then applied to identify and quantify invitro drug metabolites, yielding total drug-related material recoveries of >80% and quantitation of minor metabolites summing to 8% of the total drug-related compounds. These results highlight the strengths of simultaneous F and Cl speciation for rapid quantitation with applications in early drug development.
Here we discuss the reaction products of laser ablated alkali chlorides and elemental chlorine. Salt ablation using this technique combined with matrix-isolation spectroscopy allows for the formation and characterization of novel anionic species. The laser ablation of solid MCl with M = Cs, Rb, and K in the presence of Cl produced free [Cl] ions which were isolated in solid noble-gas matrices. For M = Cs, Rb, K, and Na, the ion pairs M[Cl] are the main reaction products. Trends in the formation and bonding of these trichloride anions will be discussed. In contrast to the trifluoride analogues, the isolated ion pairs M[Cl] feature a systematic distortion due to metal coordination.
The cohesive energy of a-fluorine, with C2/c space group symmetry, was calculated at benchmark quality by applying the method of increments. The known experimental X-ray structure data needed to be refined, since the reported intramolecular bond length was unrealistically large. At the CCSD(T) level,i ncluding corrections for zero-point energy, the basis set superposition error,a nd extrapolatedt ot he complete basis set limit, ac ohesive energy of À8.72 kJ mol À1 was calculated, whicha grees well with the 0K-extrapolated experimental value of À8.35 kJ mol À1 . [1] Comparisono ft he C2/c structure with a Cmca structure, isotypic to that of chlorine, bromine, and iodine reveals that the origin of the different structure of solidf luorine, compared to the heavier halogens,i st he lack of significantly stabilizing s-hole interactions.I na ddition, the wave numberso ft he stretching mode in solid fluorine werec alculated at coupled cluster level and compared to newly recorded Raman spectra of condensed fluorine. Both experiment and calculation indicate as light up-shiftf or the stretching mode by 2o r5cm À1 , respectively,w ith respect to af ree F 2 molecule in the gas phase.
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