Cyclopropenium cations are aromatic three-membered rings and belong to Hückel type aromatic systems. Thus, they are the smaller brothers of the well-known benzene. In contrast to benzene cyclopropenium cations were considered for a long time as curiosities without any practical relevance. However, in recent years their potential as organocatalysts has been recognized. Furthermore, polyelectrolytes carrying aminocyclopropenium subunits have been demonstrated as promising battery materials. However, there was a missing link, i.e. low molecular aminocyclopropenium-based compounds connecting features of organocatalysts and polyelectrolytes.
Recently, an international team from the University of Stuttgart, the Columbia University in New York, the Cornell University in Ittaca and the Colorado State University in Fort Collins successfully realized the synthesis and characterization of liquid crystalline aminocyclopropenium salts. These deltic ionic liquid crystals possess a cationic head group and long hydrophobic side chains. These aminocyclopropenium salts self-assemble due to the nano-segregation of immiscible molecular parts of different polarity into columnar or lamellar structures, so-called mesophases. These mesophases can be characterized via polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction thermally and structurally and serve as models for the above mentioned polyelectrolytes. The results are reported in a VIP research article in the journal Angewandte Chemie International Edition.
Molecular structure of deltic aminocyclopropenium liquid crystals, which self-assemble to columnar and lamellar mesophases. In the background a typical polarising optical microscope picture is shown.
Prof. Dr. Sabine Laschat et al.: Self‐Assembly of Aminocyclopropenium Salts: En Route to Deltic Ionic Liquid Crystals. Angewandte Chemie International Edition, März 2020. doi.org/10.1002/anie.202000824.
Prof. Sabine Laschat, University of Stuttgart, Institute of Organic Chemistry (IOC) , Phone +49 711 685 64565, E-Mail
Jeffrey S. Bandar, Colorado State University, Department of Chemistry, Fort Collins/CO, U.S.A., E-Mail
Tristan H. Lambert, Cornell University, Ittaca/NY, U.S.A., Department of Chemistry & Chemical Biology, firstname.lastname@example.org, Department of Chemistry, Columbia University, New York/NY, U.S.A.