Embedding and Positioning of Two Fe^II₄L₄ Cages in Supramolecular Tripeptide Gels for Selective Chemical Segregation

Abstract

An unreported d,l-tripeptide self-assembled into gels that embedded Fe II 4 L 4 metal-organic cages to form materials that were characterized by TEM, EDX, Raman spectroscopy, rheometry,U V/Vis and NMR spectroscopy, and circular dichroism. The cage type and concentration modulated gel viscoelasticity,and thus the diffusion rate of molecular guests through the nanostructured matrix, as gauged by 19 Fand 1 HNMR spectroscopy. When two different cages were added to spatially separated gel layers,t he gel-cage composite material enabled the spatial segregation of am ixture of guests that diffused into the gel. Each cage selectively encapsulated its preferred guest during diffusion. We thus present an ew strategy for using nested supramolecular interactions to enable the separation of small molecules. Figure 4. a) Photographofthe three-layered gel and b) 2D mapping of the 1 HNMR spectra for the three-layered gel, showing the presence of MOC 1 in layer 1( 1&Gel), the peptide alone in the buffer gel layer,a nd MOC 2 in layer 2( 2&Gel). c) 19 FNMR spectra of layer 1( top, blue) and layer 2( bottom, purple) showing, respectively,the decrease in the peak for encapsulatedT FA À (~)a nd the increase in both the encapsulated(&) and free FA (*)over time after the addition of mixed FA and ReO 4 À (1 equiv each).

Nanoscale Assembly of Functional Peptides with Divergent Programming Elements

“… 20 Research is revealing the use of heterochirality to fine-tune peptide self-assembly into a variety of nanostructures, including twisted nanofibrils, 21 , 22 nanotapes, 23 , 24 nanotubes, 25 , 26 2D-sheets, 27 or gels. 28 , 29 d -amino acids can inhibit pathological amyloid aggregation, as with d -Phe 30 on l -Phe fibrillization linked to phenylketonuria, 31 or d -Trp-Aib (Aib = aminoisobutyrric acid) on Alzheimer’s disease-related Aβ peptide. 32 Peptide inhibitors that combine a recognition motif with β-breaking Pro demonstrated promising activity in vitro and in vivo .…”

A Double‐Walled Tetrahedron with AgI4 Vertices Binds Different Guests in Distinct Sites**

“…Raman spectroscopy was used to verify the structure of cages 1 – 3 in thin films and in solution. Visible‐light Raman spectra of thin films of cages 1 – 3 were dominated by signals arising from aromatic ligand coordination to the metal centers in the region 1550–1650 cm −1 [26] . Aniline signals were not observed, confirming the absence of cage hydrolysis (Figure S39).…”

Mechanoresponsive Metal‐Organic Cage‐Crosslinked Polymer Hydrogels

“…Employing Fe‐based cages grafted with oligoethylene glycol imidazolium chains instead, conformational change upon heating allowed for the construction of a heat engine traversing multiple phase boundaries, [3b] in addition to creating permanently porous ionic liquids based on coordination cages [3c] . The groups of Nitschke and Marchesan embedded pristine cages in tripeptide gels, forming hybrid cage‐based nanostructured materials [9] . Johnson and co‐workers also contributed switchable materials based on the interconversion of Pd 3 L 6 ‐type cages and Pd 24 L 48 ‐type spheres, [10b] assemblies based on M 12 L 24 spheres, [10d,11] multi‐component assemblies, [10c] as well as complex Cu‐based gels that undergo reversible, photoredox‐induced disassembly and enable catalytic reactions within the networks [10a] .…”