Comparison of Two Different Plunger Geometries for HPTLC-MS Coupling via an Extractor-Based Interface

JPC – Journal of Planar Chromatography – Modern TLC - Plungers with two different cutting edge geometries were compared for HPTLC-MS coupling via an extractor-based interface. Their...     

Combinatorial synthesis of thin mixed oxide films and automated study of their piezoelectric properties

The development of an automated production of thin films and the characterization of their piezoelectric properties in high-throughput are described. A library of 50 undoped as well as doped lead zirconate titanate Pb(Zr,Ti)O₃ (PZT) coatings was produced by sol deposition. Afterwards, the piezoelectric properties of the library films were analyzed by automated atomic force microscopy employing the ultrasonic piezo-mode.     

Syntheses and Structure of Er6Co2.19(1)In0.81(1)

Summary. The erbium–cobalt–indide Er₆Co_2.19(1)In_0.81(1) was prepared by arc-melting of the pure elements. Single crystals were obtained through a special annealing procedure. Er₆Co_2.19(1)In_0.81(1) crystallizes with the orthorhombic Ho₆Co₂Ga structure: Immm, a = 934.3(1), b = 936.4(1), c = 985.4(1) pm, wR2 = 0.0557, 892 F ² values, and 35 variable parameters. The structure contains two gama;crystallographically independent Co₂ dumb-bells at Co–Co distances of 223 and 236 pm, respectively. Further structural motifs are distorted octahedral Er₆ clusters (336–401 pm Er–Er) which are condensed to a three-dimensional network via all corners. The In2 atoms have a distorted icosahedral erbium coordination (329–355 pm In2–Er). These icosahedra show an orthorhombically distorted bcc packing.     

Diaminodicyanoquinones: Fluorescent Dyes with High Dipole Moments and Electron‐Acceptor Properties

Fluorescent dyes are applied in various fields of research, including solar cells and light‐emitting devices, and as reporters for assays and bioimaging studies. Fluorescent dyes with an added high dipole moment pave the way to nonlinear optics and polarity sensitivity. Redox activity makes it possible to switch the molecule's photophysical properties. Diaminodicyanoquinone derivatives possess high dipole moments, yet only low fluorescence quantum yields, and have therefore been neglected as fluorescent dyes. Here we investigate the fluorescence properties of diaminodicyanoquinones using a combined theoretical and experimental approach and derive molecules with a fluorescence quantum yield exceeding 90 %. The diaminodicyanoquinone core moiety provides chemical versatility and can be integrated into novel molecular architectures with unique photophysical features.     

Cover Feature: Redox-Active Guanidines in Proton-Coupled Electron-Transfer Reactions: Real Alternatives to Benzoquinones? (Chem. Eur. J. 70/2019)

Guanidino-functionalized aromatics (GFAs) are readily available, stable organic redox-active compounds. In this work we apply one particular GFA compound, 1,2,4,5-tetrakis(tetramethylguanidino)benzene, in its oxidized form in a variety of oxidation/oxidative coupling reactions to demonstrate the scope of its proton-coupled electron transfer (PCET) reactivity. Addition of an excess of acid boosts its oxidation power, enabling the oxidative coupling of substrates with redox potentials of at least +0.77 V vs. Fc⁺/Fc. The green recyclability by catalytic re-oxidation with dioxygen is also shown. Finally, a direct comparison indicates that GFAs are real alternatives to toxic halo- or cyano-substituted benzoquinones.     

(3R*,3′R*)‐1,1′‐Dimethyl‐3,3′‐biindoline‐2,2′‐dithione

The (3R*,3′R*) configuration of the title compound, C₁₈H₁₆N₂S₂, (I), has been unambiguously elucidated by X‐­ray analysis. Mol­ecules of (I) have C₂ symmetry to a good approximation and a strongly folded shape. The interplanar angle between the two halves of a mol­ecule is 67.11 (6)°.     

Experimental and theoretical investigations of new dinuclear palladium complexes as precatalysts for the amination of aryl chlorides

A series of new palladium dinuclear species with general formula [Pd2X(mu-X)[mu-P(t)Bu2(Bph-R)]] (X = Cl, Br; Bph = biphenyl; R = H, Me, NMe2) have been prepared. The two palladium centers in these species are bridged by one of the aromatic rings of the biphenyl group present in the corresponding phosphine. The X-ray crystal structure of one of these complexes has been obtained, providing a clear picture of the bonding pattern. The stability of these dimers in solution is shown to be highly dependent on the nature of the phosphine R group and also on the bridging halide. When R = NMe2, the dimers dissociate, yielding the palladium(II) compounds PdX2[P(t)Bu2(BPh-NMe2)] (X = Cl, Br), and the X-ray crystal structure of one of them (X = Br) has shown that the biphenyl group from the phosphine interacts directly with the metal center. This interaction seems to play an important role in stabilizing the otherwise coordinatively unsaturated palladium(II) complex. In contrast, when R = H or Me, the analogous monomeric palladium(II) complexes are unstable and undergo cyclometalation to generate a palladium(II) dinuclear species in which each of the two phosphines cyclometalates with the palladium centers forming a strained four-membered ring. In addition to their unusual structures, these aryl-bridged dimers have also proven to be excellent precatalysts for the amination of aryl chlorides. To rationalize some of the experimental results, a detailed DFT computational study has been carried out and is presented herein.