Chiral and Redox‐Active Room‐Temperature Ionic Liquids Based on Ferrocene and l‐Proline

Abstract

The syntheses of room‐temperature ionic liquids (RTILs) combining the naturally occurring amino acid l‐proline and ferrocene (Fc) building blocks are reported. After quaternization of ({[(2S)‐N‐methylpyrrolidine‐2‐yl]methyleneoxy}carbonyl)ferrocene (1) with alkyl iodides and anion exchange, the resulting diastereomeric (1S,2S)‐ and (1R,2S)‐[(ferrocenylcarbonyl)oxy]methylene‐N,N‐dialkylpyrrolidine‐1‐ium RTILs are redox‐active and air‐ and water‐stable. They are also thermally stable up to 263 °C. The electrochemical FeII/FeIII potential is shifted to +0.28 V versus Fc/Fc+. Before anion exchange, several iodide derivatives were obtained as crystalline products, and their crystal structures are reported. According to the NMR spectroscopic data cation–anion aggregates are present in the non‐coordinating solvent CDCl3. In contrast, in the polar solvent [D6]dimethyl sulfoxide ([D6]DMSO), the ion pairs are separated.

Electrochemical, Spectroelectrochemical, Mößbauer, and EPR Spectroscopic Studies on Ferrocenyl‐Substituted Tritylium Dyes

“…Solvents were pre‐dried and distilled by standard procedures and degassed by saturation with nitrogen prior to use. The starting materials ferrocene carboxylic acid and methyl ferrocenecarboxylate were prepared by literature procedures . All other chemicals were obtained from commercial sources and used without further purification.…”

“…The starting materials ferrocene carboxylic acid and methyl ferrocenecarboxylate were prepared by literature procedures. [51] All other chemicals were obtained from commercial sources and used without further purification. 1 HNMR (400 MHz), 13 C{ 1 H} NMR (101 MHz), and 31 P{ 1 H} NMR (162 MHz) spectra were measured on aB ruker AvanceIII 400 spectrometer as CD 2 Cl 2 solutions at room temperature or in the solvent indicated.…”

Application of Ionic Liquids in Electrochemistry—Recent Advances

“…In 2016, Bouvet and Krautscheid [ 65 ] verified that the redox potentials of a Fe(II)/Fe(III) system using pyrrolidinium-based ILs with L-proline and ferrocene as building blocks are independent on the IL anion and on the alkyl chain length.…”

Synthesis, Chiroptical, and Redox Properties of Ferrocene‐Containing Optically Active Polymers

“…Ferrocene‐containing conjugated polymers are employed as precursors to size‐controlled metal nanoparticles, which do not form aggregates due to their carbonized residues that serve as protection reagents. The introduction of chirality into the ferrocene moieties of the polymer chain results in regularly aligned polymeric molecules based on π‐stacking which show useful properties such as molecular recognition, asymmetric catalysis, redox properties, and liquid crystallinity . Ferrocene‐based organometallic scaffolds with controlled secondary structures may also be prepared by exploiting intramolecular hydrogen‐bonding .…”

“…The introduction of chirality into the ferrocene moieties of the polymer chain results in regularly aligned polymeric molecules based on π-stacking [42] which show useful properties such as molecular recognition, [43][44][45] asymmetric catalysis, [45][46][47][48] redox properties, and liquid crystallinity. [49][50][51][52][53] Ferrocene-based organometallic scaffolds with controlled secondary structures may also be prepared by exploiting intramole cular hydrogen-bonding. [54] Ferrocene derivatives substituted with amino acids and peptides form highly structure-ordered assemblies stabilized by intermolecular hydrogen bonding between the amide moieties.…”