Two independent synthetic routes to η2-imine titanocene complexes were developed. On one hand side, ligand exchange reactions of bis(trimethylsilyl)acetylene by (p-Tolyl)HCNPh (3) employing the Rosenthal reagent Cp2Ti{η2-C2(SiMe3)2} (1) lead to Cp2Ti{η2-(p-Tolyl)CHNPh} (5), exhibiting a titanaaziridine structure. On the other hand, the direct reductive complexation of 3 by using Cp2TiCl2 (2) and Mg as reducing agent leads also to 5, one of the rare known titanoceneaziridines without additional ligands. By using the ketimine (p-Tolyl)2CNPh (4) instead of the aldimine 3, an unexpected coordination mode was found by X-ray diffraction, exhibiting an azatitanacyclopent-4-ene structure involving one tolyl fragment. In such a way, via the reductive complexation of 4, employing 2 or Cp*TiCl3 (12), the 1-aza-2-titanacyclopent-4-ene complexes 6 and 13 are formed. Density functional calculations at the M06-2X level identify these new complexes 6 and 13 as 1-aza-2-titanacyclopent-4-enes, in agreement with an analysis based on the experimental structural parameters. A theoretical study of the bonding between the titanocene fragment and the imine ligand reveals that steric factors are more pronounced for titanaaziridines and disfavor their formation compared to azatitanacyclopentenes. This provides a rationalization for the preferred formation of titanoceneaziridines in the case of aldimine ligands and azatitanacyclopentenes when ketimines are applied. Whereas titanoceneaziridine 5 undergoes insertion reactions into the Ti–C carbon σ-bond with aldehydes, ketones, or carbodiimides to the five-membered titanacycles 20 and 21, complex 6 appears to be inert in comparable reactions.

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Electrodes in lithium‐ion and post‐lithium‐ion batteries are made of composite materials exposing a variety of different surfaces towards the electrolyte. This causes a distribution of current densities and consequently locally different changes of interfaces and bulk materials that might be critical for the performance and durability of secondary batteries. The optimization of local structures of battery materials is hindered by a lack of local techniques that provide in situ reactivity information from such hidden interfaces. A variety of new electrochemical scanning probe techniques are currently adapted to the investigation of battery materials under near‐realistic environmental conditions. The review provides a critical assessment of this development with a particular emphasis on the assessment of the passivating properties of solid–electrolyte interphases, the extension of the concepts to lithium–oxygen cells, and attempts to image ion intercalation reactions.

Gas diffusion electrodes (GDEs) for high-temperature polymer electrolyte fuel cells with different sizes of the used binder particles were evaluated by scanning electrochemical microscopy (SECM) with shear force (SF) supplement. The SF data provide means of checking the substrate morphology with respect to cracks formed during the drying process and with respect to aggregates from used binder of poly(fluoroethylene) (PTFE) simultaneously to the electrochemical data. Electron microscopy results show that a GDE prepared with smaller PTFE particles exhibits less PTFE aggregation and more regular cracks. The SECM images show a more homogeneous distribution and higher level of oxygen reduction reaction activity for the GDE prepared with smaller PTFE particles. The quantitative comparison is enabled by the SF setup that maintains a constant working distance toward the sample in the variant of the redox competition mode, in which a cyclic voltammogram was recorded for every grid position of the microelectrode probe. Mass transport limitations of oxygen during the experiment are avoided by dedicated shape of the microelectrode body. Images of microelectrode currents at specific potentials were extracted to map the local electrocatalytic activity of the GDE. The GDEs were processed to membrane electrode assemblies and applied in HT-PEFC single cell tests. The polarization curve agree with the SECM results that GDEs produced with smaller PTFE particles favor the MEA performance. The concept of zero-emission requires a rapid shift from traditional fuels to next generation of clean technologies 1 to mitigate local pollution in urban areas and to mitigate the emission of carbon dioxide. Polymer electrolyte water electrolyzers for the hydrogen production (from solar and wind power) and polymer electrolyte fuel cells (PEFC) for electricity production from hydrogen are considered one of the most promising clean power technologies. Both electrochemical components are equipped with membrane electrode assemblies (MEAs) consisting either of gas diffusion electrodes (GDEs) assembled with membranes or catalyst coated membranes (CCMs) combined with gas diffusion layers (GDLs). 2,3 In the high-temperature polymer electrolyte fuel cell (HT-PEFC), which is considered here, GDEs are commonly used. In order to apply the catalyst dispersion onto the GDL, various coating methods can be used such as blade coating, spraying and screen printing. [4][5][6] During the subsequent drying process of the dispersion, cracks in the catalyst layer may occur, 4,7 which segment the catalyst layer into parts of a few hundred micrometers extension. The cracks, which are clearly visible, are not electrochemically active. A review about the formation and analysis of the crack structure as well as an ex-situ analysis of the crack width distribution in GDEs of HT-PEFCs was given by Froning et al. 8,9 However, it is not yet clear how the crack structures within the catalyst layers affect the performance of the fuel cell. Furthermore, the influence of the morphol...

Control of the cell adhesion and growth on chemically patterned surfaces is important in an increasing number of applications in biotechnology and medicine, for example implants, in-vitro cellular assays, and biochips. This review covers patterning techniques for organic thin films suitable for site-directed guidance of cell adhesion to surfaces. Available surface patterning techniques are critically evaluated, with special emphasis on surface chemistry that can be switched in time and space during cultivation of cells. Examples from the authors' laboratory include the use of cell-repellent self-assembled monolayers (SAM) terminated by oligoethylene glycol (OEG) units and the lifting of the cell repellent properties by use of electrogenerated Br2/HOBr which can be performed with positionable microelectrodes. Structural changes of the SAM were analyzed by polarization-modulated infrared reflection absorption spectroscopy (PM IRRAS). Use of a soft array system of individually addressable microelectrodes enables formation of flexible and complex patterns in a short time and has the potential for further acceleration of probe-induced local manipulation of cell adhesion.

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Scanning ohmic microscopy (SOM) detects a current by the potential difference along the current line. Using two microreference electrodes (MREs) and a very close distance to the electrode surface of interest, this principle can be used to record local current densities independently of the reaction that causes the current flow (ion or electron transfer processes). Ion transfer processes are difficult to image by scanning electrochemical microscopy (SECM). Here we present technical details of our SOM setup with possible extension required for the analysis of battery materials. In this respect, the selection of the specific voltage probes is explored for different applications. Our concept further uses voltage programs, for example, cyclic voltammetry, at each grid point of the image and the integration of specific voltage ranges to obtain material‐specific signals, and is extended by the use of a shear‐force detection unit at inclined capillaries for topographical imaging and an accurate vertical positioning of the probe.