Glymes as Versatile Solvents for Chemical Reactions and Processes: from the Laboratory to Industry

Glymes, also known as glycol diethers, are saturated non-cyclic polyethers containing no other functional groups. Most glymes are usually less volatile and less toxic than common laboratory organic solvents; in this context, they are more environmentally benign solvents. However, it is also important to point out that some glymes could cause long-term reproductive and developmental damages despite their low acute toxicities. Glymes have both hydrophilic and hydrophobic characters that common organic solvents are lack of. In addition, they are usually thermally and chemically stable, and can even form complexes with ions. Therefore, glymes are found in a broad range of laboratory applications including organic synthesis, electrochemistry, biocatalysis, materials, and Chemical Vapor Deposition (CVD), etc. In addition, glyme are used in numerous industrial applications, such as cleaning products, inks, adhesives and coatings, batteries and electronics, absorption refrigeration and heat pumps, as well as pharmaceutical formulations, etc. However, there is a lack of comprehensive and critical review on this attractive subject. This review aims to accomplish this task by providing an in-depth understanding of glymes' physicochemical properties, toxicity and major applications.

Lanthanide Compounds with Fluorinated OC6F5 Ligands: Homo- and Heterovalent Complexes of Eu(II) and Eu(III)

The fluorinated phenoxide OC6F5 forms the stable Eu(II) and Eu(III) derivatives (DME)2Eu(mu-OC6F5)3Eu(mu-OC6F5)3Eu(DME)2 and (DME)2Eu(OC6F5)3, as well as the heterovalent product (DME)2Eu(mu-OC6F5)3Eu(DME)(OC6F5)2, in redox reactions of Eu with HOC6F5 or in proton-transfer reactions of HOC6F5 with Eu(SPh)2. The divalent complex crystallizes as a trimer with three bridging phenoxides bridging each pair of metals, with the terminal metals coordinating DME and the central metal ion encapsulated totally by O(C6F5) and dative fluoride interactions. The trivalent compound is monomeric with terminal phenoxide ligands and no Eu-F interactions. The heterovalent compound has clearly localized metal valence states and coordination features that mimic the homovalent species with the terminal OC6F5 bound to the Eu(III) ion, three bridging OR ligands spanning the Eu(II) and Eu(III) ions, and dative Eu(II)-F bonds. At elevated temperatures, these compounds decompose to give a mixture of solid-state fluoride phases.

Synthesis and characterization of volatile, fluorine-free beta-ketoiminate lanthanide MOCVD precursors and their implementation in low-temperature growth of epitaxial CeO(2) buffer layers for superconducting electronics

A new class of volatile, low-melting, fluorine-free lanthanide metal-organic chemical vapor deposition (MOCVD) precursors has been developed. The neutral, monomeric Ce, Nd, Gd, and Er complexes are coordinatively saturated by a versatile, multidentate ether-functionalized beta-ketoiminato ligand series, the melting point and volatility characteristics of which can be tuned by altering the alkyl substituents on the keto, imino, and ether sites of the ligand. Direct comparison with conventional lanthanide beta-diketonate complexes reveals that the present precursor class is a superior choice for lanthanide oxide MOCVD. Epitaxial CeO(2) buffer layer films can be grown on (001) YSZ substrates by MOCVD at significantly lower temperatures (450-650 degrees C) than previously possible by using one of the newly developed cerium beta-ketoiminate precursors. Films deposited at 540 degrees C have good out-of-plane (Deltaomega = 0.85 degrees ) and in-plane (Deltaphi = 1.65 degrees ) alignment and smooth surfaces (rms roughness approximately 4.3 A). The film growth rate decreases and the films tend to be smoother as the deposition temperature is increased. High-quality yttrium barium copper oxide (YBCO) films grown on these CeO(2) buffer layers by pulsed organometallic molecular beam epitaxy exhibit very good electrical transport properties (T(c) = 86.5 K, J(c) = 1.08 x 10(6) A/cm(2) at 77.4 K).