Ionic Liquid Crystals Derived from Amino Acids

Abstract

Novel chiral amino acid derived ionic liquid crystals with amine and amide moieties as spacers between the imidazolium head group and the alkyl chain were synthesised. The key step in the synthesis utilised the relatively uncommon SO3 leaving group in a microwave-assisted reaction. The mesomorphic properties of the mesogens were determined by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction. All liquid crystalline salts exhibit a smectic A mesophase geometry with strongly interdigitated bilayer structures. An increase of the steric bulk of the stereogenic centre hindered the formation of mesophases. In case of phenylalanine-derived derivatives a mesomorphic behaviour was observed for shorter alkyl chains as compared to other amino acid derivatives indicating an additional stabilising effect by the phenyl moiety.

A Comprehensive Study on Lyotropic Liquid–Crystalline Behavior of an Amphiphile in 20 Kinds of Amino Acid Ionic Liquids

“…Taking these resultsi nto account,w ea ssume that the birefringent mesophases observedf or 1/[C4mim][Phe] at molar ratios of 5:5and 4:6a re not Lphases butother mesophases.The exhibitiono fLCproperties under IL-rich conditions has been also confirmed by X-ray diffraction (XRD)m easurement. Previously,L aschat et al [36] examined the thermotropic LC behavioro faseries of amphiphilic imidazolium salts having an atural amino acid moiety in their structures.A mong them,t hose having ap henylalanine moiety show an exceptional LC behavior that is differentf rom those having another amino acid moiety.T he authors attributed this to an ability of the phenylu nits to form p-p interactions. Previously,L aschat et al [36] examined the thermotropic LC behavioro faseries of amphiphilic imidazolium salts having an atural amino acid moiety in their structures.A mong them,t hose having ap henylalanine moiety show an exceptional LC behavior that is differentf rom those having another amino acid moiety.T he authors attributed this to an ability of the phenylu nits to form p-p interactions.…”

“…Considering the molecular structure of 1 and the weight fraction of [C4mim][Phe] in the mixtures, we assumedt hat the birefringent mesophase formed by 1/[C4mim][Phe]i san ormal columnar phasew here the ionophobic parts form inner domains surrounded by the ionophilic components, although we have not obtained enough resultsf or identifying the mesophase as an ormalc olumnar phase. Previously,L aschat et al [36] examined the thermotropic LC behavioro faseries of amphiphilic imidazolium salts having an atural amino acid moiety in their structures.A mong them,t hose having ap henylalanine moiety show an exceptional LC behavior that is differentf rom those having another amino acid moiety.T he authors attributed this to an ability of the phenylu nits to form p-p interactions. In our case, it is reasonable to conclude that the exceptional LC behavior of 1/[C4mim][Phe] resultsf rom the formation of p-p interactions between [Phe] anions.…”

Convenient Approach to 2‐Substituted (Thio)morpholin‐3‐ones from α‐Diazoacetates via X‐H Carbene Insertion – Lactamization Sequence

“…General considerations . N ‐Boc protected 2‐aminoethanol, 2‐(methylamino)ethanol, 2‐aminoethanethiol, ( S )‐methyl 2‐amino‐3‐mercaptopropanoate, methyl 2‐diazo‐2‐(4‐nitrophenyl)acetate and methyl 2‐diazo‐2‐(phenylsulfonyl)acetate, 3‐diazodihydrofuran‐2(3 H )‐one were prepared according literature methods, other reagents were obtained from commercial sources and used without additional purification. Tetrahydrofuran and dichloromethane were distilled from suitable drying agents.…”

Tyrosine‐Based Ionic Liquid Crystals: Switching from a Smectic A to a Columnar Mesophase by Exchange of the Spherical Counterion

“…We recently reported imidazolium ILCs 2 , which were prepared from amino acids 1 (Scheme ). These ILCs formed SmA mesophases with phase widths up to 70 K and clearing points below 120 °C, but the synthesis was strenuous and had a poor overall yield.…”

“… Previous work on imidazolium ILCs 2 based on natural amino acids and our envisioned synthetic strategy to double‐tailed ILCs 3 and 4 starting from l ‐tyrosine 5 .…”