Johannes Sackmann

Bio: Johannes Sackmann is an academic researcher from RWTH Aachen University. The author has contributed to research in topics: Ultrasonic welding & Ultrasonic sensor. The author has an hindex of 7, co-authored 28 publications receiving 223 citations.

CH-Anion versus anion-π interactions in the crystal and in solution of pentafluorobenzyl phosphonium salts

Abstract: A series of phosphonium salts with pentafluorobenzyl substituents have been synthesized and were investigated in the crystal as well as in solution. The solid state structures of 1a, 1b and 2d reveal the presence of anion-π as well as CH-anion interactions. The two attractive, yet competitive forces seem to act in concert and a directing effect of the CH interaction on the relative position between anion and π-system is observed. The search for anion-π interactions in solution failed. Only CH-anion interactions proved to be important in solution.

Tools for ultrasonic hot embossing

Abstract: Ultrasonic hot embossing has been developed in recent years enabling quick and flexible fabrication of micro structures from thermoplastic polymers. This paper describes many possibilities of the fabrication, use, and limits of tools for this process. Tools have been produced by milling, drilling, silicon etching, photo and X-ray lithography, and electroplating and by combining these processes.

Anion Recognition Strategies Based on Combined Noncovalent Interactions.

Abstract: This review highlights the most significant examples of an emerging field in the design of highly selective anion receptors. To date, there has been remarkable progress in the binding and sensing of anions. This has been driven in part by the discovery of ways to construct effective anion binding receptors using the dominant N–H functional groups and neutral and cationic C–H hydrogen bond donors, as well as underexplored strong directional noncovalent interactions such as halogen-bonding and anion−π interactions. In this review, we will describe a new and promising strategy for constructing anion binding receptors with distinct advantages arising from their elaborate design, incorporating multiple binding sites able to interact cooperatively with anions through these different kinds of noncovalent interactions. Comparisons with control species or solely hydrogen-bonding analogues reveal unique characteristics in terms of strength, selectivity, and interaction geometry, representing important advances in t...

Anion Induced Formation of Supramolecular Associations Involving Lone pair−π and Anion−π Interactions in Co(II) Malonate Complexes: Experimental Observations, Hirshfeld Surface Analyses and DFT Studies

Abstract: Three Co(II)–malonate complexes, namely, (C5H7N2)4[Co(C3H2O4)2(H2O)2](NO3)2 (1), (C5H7N2)4[Co(C3H2O4)2(H2O)2](ClO4)2 (2), and (C5H7N2)4[Co(C3H2O4)2(H2O)2](PF6)2 (3) [C5H7N2 = protonated 2-aminopyridine, C3H4O4 = malonic acid, NO3– = nitrate, ClO4– = perchlorate, PF6– = hexafluorophosphate], have been synthesized from purely aqueous media, and their crystal structures have been determined by single crystal X-ray diffraction. A thorough analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions in 1–3, which are crucial in building supramolecular architectures. When these complexes are structurally compared with their previously reported analogous Ni(II) or Mg(II) compounds, a very interesting feature regarding the role of counteranions has emerged. This phenomenon can be best described as anion-induced formation of extended supramolecular networks of the type lone pair−π/π–π/π–anion−π/π–lone pair and lone pair−π/π–π/π–anion involving various weak forces lik...

Experimental Quantification of Anion−π Interactions in Solution Using Neutral Host–Guest Model Systems

Abstract: Chemical intuition suggests that anions and π-aromatic systems would repel each other. Typically, we think of cations as being attracted to electron-rich π-systems of aromatic rings, and the cation−π interaction, a well-established noncovalent interaction, plays an important role in nature. Therefore the anion−π interaction can be considered the opposite of the cation−π interaction. Computational studies of simple models of anion−π interactions have provided estimates of the factors that govern the binding geometry and the binding energy, leading to a general consensus about the nature of these interactions. In order to attract an anion, the charge distribution of the aromatic system has to be reversed, usually through the decoration of the aromatic systems with strongly electron-withdrawing groups. Researchers have little doubt about the existence of attractive anion−π interactions in the gas phase and in the solid state. The bonding energies assigned to anion−π interactions from quantum chemical calcula...