Shape-persistent macrocycles: efficient extraction towards lanthanide and actinide elements

Abstract

The extraction of three shape-persistent aromatic oligoamide macrocycles (cycloaramides) bearing either apolar or polar side chains at the periphery of the rings has been investigated towards some representative lanthanide and actinide ions, and alkali metal ions. The results from the liquid-liquid extraction of lanthanide and thorium ions from aqueous solutions into dichloromethane revealed remarkably high extractability of up to 99% and selectivity over alkali metal cations. The stoichiometry of the complex formed between the macrocycle and Eu 3? or Th 4? was determined to be 1:1.

Solvent extraction of thorium(IV) and rare earth elements with novel polyaramide extractant containing preorganized chelating groups

“…The resulting product was characterized by 1 H NMR, GPC and FT‐IR techniques. The 1 H NMR spectrum of polymer 1 recorded in CDCl 3 revealed several sets of signals for NH, aromatic protons (internal and external) that correspond to those signals observed in the oligoamides previously reported (see Supporting Information) . The difference between 1 and its lower oligoamides counterparts is the considerable broadening of all signals, strongly suggesting the formation of larger polymeric species.…”

“…Recently we have reported the efficient extraction of lanthanide and actinide elements using cyclo[6]aramides . Interestingly, the acyclic species of these shape‐persistent macrocycles revealed higher selectivity and efficiency towards Hg 2+ over other metal cations .…”

A Redox‐Responsive Complex System Based on 2 D Shape‐Persistent Cyclo[6]aramide and Ferrocenium

“…Hydrogen‐bonded (H‐bonded) macrocycles with a constrained conformation have evolved in recent years into many different types of supramolecular hosts since its first conception proposed two decades ago . With the synthetic simplicity and unique structural features such as hydrophilic cavity, some H‐bonded aromatic amide macrocycles have found intriguing applications in molecular recognition, catalysis, separation technology, and transmembrane channels . Among them, a class of H‐bonded cyclic compounds in which each aromatic amide residue is connected via amide linkages with the carbonyl oxygens pointing inwards are particularly noteworthy .…”

“…Cyclo[6]aramide 1 is able to form a 1:1 inclusion complex with Fc + and its analogue cobaltocenium ( Cob + ) with a striking difference in the binding affinity as compared to the reduced form ( Fc ). Previous work has shown that H‐bonded aromatic amide macrocycles are able to complex larger metal cations, such as Cs + or lanthanides, but no attempt has been made to date for the binding of organometallic molecule. This study offers the first example of 2D H‐bonded aromatic amide macrocycles that could interact with the organometallic compound‐based guests.…”

Two‐Component Supramolecular Gels Derived from Amphiphilic Shape‐Persistent Cyclo[6]aramides for Specific Recognition of Native Arginine

“…[20] With their shape-persistent aromatic surfaces, the macrocycles carrying extra-annular alkyl side chains are prone to self-aggregation in both polar and nonpolar solvents as a consequence of the cooperative action of dipole-dipole and p-p stacking interactions. [21] With their correctly arranged amide oxygen atoms pointing inwards, the near-planar six-residue macrocycles, [22] dubbed cyclo [6]aramides, have shown highly selective recognition of guanidinium ions, [23] efficient separation of metal ions, [24] and a high affinity for dialkylammonium salts. [25] Remarkably, a cyclo [16]aramide with a larger nanosized cavity could accommodate even a depsipeptide antibiotic valinomycin.…”