l‐Valine Derivatised 1,3,5‐Benzene‐Tricarboxamides as Building Blocks for a New Supramolecular Organogel‐Like Alignment Medium

Abstract

We were previously able to demonstrate that mesogens self‐assembled from small molecules, more specifically 1,3,5‐benzene‐tricarboxamides (BTAs), are capable of forming lyotropic liquid crystalline phases in chloroform and CCl4, which are suitable for use as alignment media for small organic molecules. In this context, however, it became quickly apparent that one major limitation of such systems arises from the disruption of the self‐assembly process by certain analytes. Here, we present a modified version of our original BTA‐monomers, containing an additional l‐valine moiety. Through this modification, the number of available hydrogen‐bond acceptors/donators per monomer is doubled, resulting in vastly increased stability. The new system thus obtained exhibits anisotropic properties at much lower concentrations of BTA and allows for the determination of residual dipolar couplings for previously incompatible analytes like isopinocampheol (IPC). Interestingly, the BTA system exhibits the properties of an organogel rather than of a liquid crystal. This is thus the first report of the use of an organogel‐like alignment medium.

Investigations into Supramolecular Lyotropic Liquid Crystals Based on 1,3,5‐Benzenetricarboxaramides by NMR Spectroscopy

“…In order to answer the question how the obtained LLC phases react to the addition of further components, we have prepared mixtures containing the same two analytes (Figure 3) used in earlier studies: [8,18] (−)‐ β ‐pinene and (−)‐isopinocampheol (IPC). Of these, the latter was previously shown to interact strongly with the BTA LLC phase [8] .…”

“… General BTA structure (left) and sidechains investigated in this work ( 1 a – h , in the following denoted BTAr‐C n ) and those utilized for alignment media in earlier publications ( 2 [8] and 3 [18] ). …”

“…This made the extraction of anisotropic observables impossible for this particular analyte. While we were able to provide remedy for these issues by doubling the number of hydrogen bond donor/acceptor functions per BTA molecule ( 3 ), [18] this also caused the system to behave gel‐like [34] and necessitated a more complicated preparation.…”

“…Apart from these fundamental studies, BTA-based lyotropic mesophases have also been utilized as so called alignment media in NMR spectroscopy: [8,18] In this application the inherent order of such lyotropic liquid crystalline (LLC) or gel phases is exploited to induce a preferential orientation ("alignment") of dissolved analytes in relation to the external magnetic field (with the sample then composed of the analyte, the solvent and a component inducing orientation, here a BTA). This in turn makes anisotropic interactions [28][29][30][31][32] observable even in solution.…”

Synthesis and characterization of novel organo-hydrogel based agar, glycerol and peppermint oil as a natural drug carrier/release material

“…Medicines containing active ingredients from peppermint include colpermin (187 mg Menthol), Salonpas (3% menthol), Camfolin (10%), and Otrivine menthol (0.10%) [ 13 , 14 ]. Essential oils, which are among the various active ingredients in peppermint species, are used in the polymer and industrial fields [ [15] , [16] , [17] , [18] , [19] , [20] , [21] ].…”