Development of novel supramolecular alignment media based on 1,3,5-benzenetricarboxamides (BTAs)
Organic Molecular Chemistry - Synthesis and Characterisation
Final Report Abstract
Nuclear magnetic resonance spectroscopy (NMR spectroscopy) makes important contributions to the structure elucidation and characterization of biologically relevant compounds and to the investigation of structure-activity relationships of these compounds to further improve their properties. To complement classical NMR methods such as the analysis of chemical shifts, scalar couplings and nuclear Overhauser enhancement (NOE), so-called residual dipolar couplings (RDCs) have become more widely used in recent years. These anisotropic NMR parameters only become observable when the investigated compounds are introduced into an anisotropic environment, e.g. an anisotropically swollen gel or a lyotropic liquid crystalline phase. The classic polymer materials used to form these so-called alignment media in organic solvents often have to be synthesized and purified tediously. As an alternative approach, low-molecular weight compounds such as 1,3,5-benzentricarboxamides (BTAs), which form supramolecular stacks in solution through self-assembly, can also be used as alignment media analogous to polymers. The intermolecular interactions (e.g. hydrogen bonds, π-π stacking interactions, etc.) required to stabilize the highly dynamic self-assemblies are influenced by a variety of factors. The structure of the BTAs with an aromatic core and amide side chains enables great variability and allows the influencing factors on the aggregation behavior to be specifically addressed by a clever choice of substituents. As part of the project, already established BTA systems were improved and new structural motifs were specifically produced as BTAs, in each case with the aim of a broadly applicable, more controllable application as alignment medium in the RDC-based structural elucidation of small organic compounds. By introducing an amino acid or ester functionality in the side chain, additional intermolecular hydrogen bonds can be established, which significantly improves the stability towards interfering solvents or analytes. If instead less strong intermolecular stacking interactions are formed by introducing aryl residues with alkyl chains of varying length, this novel BTA system makes it possible to systematically investigate the influence of the solubilitymediating groups on the aggregation behavior. Furthermore, BTA systems for polar solvents based on azosulfonic acid side chains have also been established and successfully used for the RDC analysis of polar analytes in water. The project has so far resulted in three peer-reviewed publications, another on chiral sergeant-and-soldier BTA systems is in preparation.
Publications
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“L-Valine-modified BTAs as Building Blocks for Alignment Media in Organic Structure Determination using NMR”, ORCHEM 2018, Berlin, 09/2018.
K. Knoll, M. Leyendecker & C. M. Thiele
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l‐Valine Derivatised 1,3,5‐Benzene‐Tricarboxamides as Building Blocks for a New Supramolecular Organogel‐Like Alignment Medium. European Journal of Organic Chemistry, 2019(4), 720-727.
Knoll, Kevin; Leyendecker, Martin & Thiele, Christina M.
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A supramolecular and liquid crystalline water‐based alignment medium based on azobenzene‐substituted 1,3,5‐benzenetricarboxamides. Magnetic Resonance in Chemistry, 60(6), 563-571.
Knoll, Kevin; Herold, Dominik; Hirschmann, Max & Thiele, Christina M.
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Front Cover: Investigations into Supramolecular Lyotropic Liquid Crystals Based on 1,3,5‐Benzenetricarboxaramides by NMR Spectroscopy (Eur. J. Org. Chem. 11/2022). European Journal of Organic Chemistry, 2022(11).
Knoll, Kevin; Kostner, Tobias; Lorenz, Christian & Thiele, Christina M.
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Investigations into Supramolecular Lyotropic Liquid Crystals Based on 1,3,5‐Benzenetricarboxaramides by NMR Spectroscopy. European Journal of Organic Chemistry, 2022(11).
Knoll, Kevin; Kostner, Tobias; Lorenz, Christian & Thiele, Christina M.
