Synthesis and Crystal Structures of Novel Copper(I) Clusters with Bridging Silyl Amide Ligands

Treatment of copper(I) chloride with R₂Si(NLiPh)₂ (R = Me, Ph) in thf led to the formation of the octanuclear cluster compounds [Cu₈{(R₂Si(NPh)₂}₄] [R = Me ( 1 ), Ph ( 2 ).] Compound 1 crystallizes in the tetragonal space group P4/n, with a = 1505.41(5) and c = 1911.32(7) pm. The X‐ray crystal structure determination revealed a cube shaped Cu₈ cluster core with μ₄ bridging Me₂Si(NPh)₂^2– ligands. The copper atoms display an almost linear coordination with Cu–N distances in the range of 191.1(3)–191.4(3) pm. The Cu–Cu distances are 265.7(1)–267.3(1) pm. Compound 2 forms monoclinic crystals, space group P2₁/n, with a = 1461.87(4), b = 2483.77(6), c = 2725.49(8) pm, β = 100.77(1)°. The cluster core of compound 2 consists formally of two mutually perpendicular arranged trigonal prisms, which share a common square face. Like in the case of compound 1 the square faces of the cluster core are capped by μ₄ bridging Ph₂Si(NPh)₂^2– ligands. The copper atoms adopt a nearly linear N–Cu–N coordination with Cu–N distances of 190.0(4)–195.1(4) pm. The Cu–Cu distances are 252.3(1)–305.6(1) pm.     

Analysis of monoclonal antibody by a novel CE‐UV/MALDI‐MS interface

mAbs are highly complex proteins that present a wide range of microheterogeneity that requires multiple analytical methods for full structure assessment and quality control. As a consequence, the characterization of mAbs on different levels is particularly product‐ and time‐consuming. CE‐MS couplings, especially to MALDI, appear really attractive methods for the characterization of biological samples. In this work, we report the last instrumental development and performance of the first totally automated off‐line CE‐UV/MALDI‐MS/MS. This interface is based on the removal of the original UV cell of the CE apparatus, modification of the spotting device geometry, and creation of an integrated delivery matrix system. The performance of the method was evaluated with separation of five intact proteins and a tryptic digest mixture of nine proteins. Intact protein application shows the acquisition of electropherograms with high resolution and high repeatability. In the peptide mapping approach, a total number of 154 unique identified peptides were characterized using MS/MS spectra corresponding to average sequence coverage of 64.1%. Comparison with NanoLC/MALDI‐MS/MS showed complementarity at the peptide level with an increase of 42% when using CE/MALDI‐MS coupling. Finally, this work represents the first analysis of intact mAb charge variants by CZE using an MS detection. Moreover, using a peptide mapping approach CE‐UV/MALDI‐MS/MS fragmentation allowed 100% sequence coverage of the light chain and 92% of the heavy chain, and the separation of four major glycosylated peptides and their structural characterization.     

A Robust Algorithm for Roots Selection and Saturation Pressure Calculation for Cubic Equations of State

Journal of Solution Chemistry - In this work, a robust and rigorous procedure for roots calculation and selection for a Cubic Equation of State is presented. Roundoff errors are detected and...     

Carbazole-Based Colorimetric Anion Sensors

Owing to their strong carbazole chromophore and fluorophore, as well as to their powerful and convergent hydrogen bond donors, 1,8-diaminocarbazoles are amongst the most attractive and synthetically versatile building blocks for the construction of anion receptors, sensors, and transporters. Aiming to develop carbazole-based colorimetric anion sensors, herein we describe the synthesis of 1,8-diaminocarbazoles substituted with strongly electron-withdrawing substituents, i.e., 3,6-dicyano and 3,6-dinitro. Both of these precursors were subsequently converted into model diamide receptors. Anion binding studies revealed that the new receptors exhibited significantly enhanced anion affinities, but also significantly increased acidities. We also found that rear substitution of 1,8-diamidocarbazole with two nitro groups shifted its absorption spectrum into the visible region and converted the receptor into a colorimetric anion sensor. The new sensor displayed vivid color and fluorescence changes upon addition of basic anions in wet dimethyl sulfoxide, but it was poorly selective; because of its enhanced acidity, the dominant receptor-anion interaction for most anions was proton transfer and, accordingly, similar changes in color were observed for all basic anions. The highly acidic and strongly binding receptors developed in this study may be applicable in organocatalysis or in pH-switchable anion transport through lipophilic membranes.     

Fabrication and characterization of n-ZnO on p-SiC heterojunction diodes on 4H-SiC substrates

We report on the growth and characterization of n-ZnO/p-4H-SiC heterojunction diodes. Our n-ZnO layers were grown with radical-source molecular beam epitaxy (RS-MBE) on p-4H-SiC epilayers, which was previously prepared in a horizontal hot-wall reactor by chemical vapour deposition (CVD) on the n-type 4H-SiC wafers. Details on the n-ZnO growth on 8-off 4H-SiC wafers, the quality of the layers and the nature of realized p–n structures are discussed. Mesa diode structures were fabricated. Al was sputtered through a circle mask with diameter 1 mm and annealed to form Ohmic contacts to p-SiC. Ohmic contacts to the n-ZnO were formed by 30 nm/300 nm Ti/Au sputtered by electron beam evaporation. Electrical properties of the structures obtained have been studied with Hall measurements, and current–voltage measurements (I–V). I–V measurements of the device showed good rectifying behavior, from which a turn-on voltage of about 2 V was obtained.     

On the Rotational Intergrowth of Hierarchical FAU/EMT Zeolites

A structural study of a hierarchical zeolite X, which is similar to the one first synthesized by Inayat et al., 12 was performed using transmission electron microscopy imaging and diffraction. Evidence is provided, by comparison to simulations, that this material is an intergrowth of FAU and EMT and a conceptual model is presented for the growth of the FAU material with a small fraction of EMT in an atypical morphology of assembled sheets with well‐defined intersection angles.     

Reversible Re‐programing of Cell–Cell Interactions

The ability to engineer and re‐program the surfaces of cells would provide an enabling synthetic biological method for the design of cell‐ and tissue‐based therapies. A new cell surface‐engineering strategy is described that uses lipid‐chemically self‐assembled nanorings (lipid‐CSANs) that can be used for the stable and reversible modification of any cell surface with a molecular reporter or targeting ligand. In the presence of a non‐toxic FDA‐approved drug, the nanorings were quickly disassembled and the cell–cell interactions reversed. Similar to T‐cells genetically engineered to express chimeric antigen receptors (CARS), when activated peripheral blood mononuclear cells (PBMCs) were functionalized with the anti‐EpCAM‐lipid‐CSANs, they were shown to selectively kill antigen‐positive cancer cells. Taken together, these results demonstrate that lipid‐CSANs have the potential to be a rapid, stable, and general method for the reversible engineering of cell surfaces and cell–cell interactions.     

Tetracyanoquinodimethane Reduction by Complexed Guanidinyl‐Functionalized Aromatic Compounds

In this work, we report on the reduction of tetracyanoquinodimethane (TCNQ) with dicationic complexes of guanidinyl‐functionalized aromatic (GFA) electron donors. In contrast to reduction with free GFAs, milder reduction conditions were achieved, and this led to semiconducting materials with extended TCNQ π stacking. The charge on the TCNQ units was estimated from the structural data obtained by single‐crystal X‐ray diffraction analysis and from IR spectroscopic data. The electrical conductivity was studied and the activation energy of the semiconducting materials was estimated from the temperature dependence of the conductivity.     

Palladium(II) saccharinate complexes trans-[Pd(sac)2(LH)2] with amino- and acetylamino-pyridine co-ligands: molecular structures of trans-[PdCl2(2-ampyH)2].2dmf (2-ampyH = 2-amino-3-methylpyridine) and trans-[Pd(κ2-2-acmpy)2] (2-acmpyH = 2-acetylamino-3-methylpyridine)

Reaction of Na₂[PdCl₄] with two equivalents of amino- or acetylamino-pyridines (LH) affords trans-[PdCl₂-(LH)₂] {LH = 2-amino-3-methylpyridine (2-ampyH), 3-aminopyridine (3-apyH), 2-acetylamino-3-methylpyridine (2-acmpyH), 3-acetylamino-pyridine (3-acpyH)}. An X-ray crystal structure of trans-[PdCl₂(2-ampyH)₂] shows that the 2-ampy-H ligands are coordinated in a monodentate fashion via the nitrogen atoms of the pyridine rings. Treatment of trans-[PdCl₂(2-acmpyH)₂] with NEt₃ affords the cyclometalated complex, trans-[Pd(κ²-2-acmpy)₂], the X-ray structure of which shows that the 2-acmpy ligand is coordinated to palladium in a bidentate fashion via the nitrogen atom of the pyridine ring and oxygen. Reaction of trans-[PdCl₂(LH)₂] with two equivalents of sodium saccharinate affords the bis(saccharinate) complexes, trans-[Pd(sac)₂(LH)₂], in which the saccharinate anions are coordinated via the amide nitrogen atom.