Aromatic foldamers as scaffolds for metal second coordination sphere design

Abstract

As metalloproteins exemplify, the chemical and physical properties of metal centers depend not only on their first but also on their second coordination sphere. Installing arrays of functional groups around...

Whither Second-Sphere Coordination?

“…Huc [97][98][99][100] has presented (Figure 5a) the chemical community with several examples of molecular recognition through second-sphere coordination using molecular capsules formed by metalcoordination-directed folding of a helical oligomer. A key chain-segment, pyridazine-pyridinepyridazine (pyz-pyr-pyz), was introduced into the oligomer.…”

“…Here, the Cu 2+ center interacts with the substrate through second-sphere coordination involving solvents -a H 2 O and a MeOH 8 molecule -that are coordinated directly to the metal ion. As an extension of such molecular recognition, the authors also developed a new strategy 100 to prepare the foldamer capsule shells around a [2Fe-2S] cluster. The foldamer shell influences the structural and spectroscopic properties of the metal cluster, including desymmetrization and confinement of part of its first coordination sphere within the foldamer cavity.…”

α‐Amino‐iso‐Butyric Acid Foldamers Terminated with Rhodium(I) N‐Heterocyclic Carbene Catalysts

“…Within this latter area, several classes of foldamers, including protein‐foldamer hybrids, [2–4] have been shown to have catalytic activity that is either dependent upon or modulated by their folded structure [5–11] . Metal complexes, integrated within or pendant to a foldamer, can act as catalysts [11] or provide essential structural motifs, [12,13] including responsive centres that can alter the folded state [14] or reporters of stereochemical complexity [15–17] . A diverse set of reactions has been catalysed by foldamers bearing metal complexes, such as hydrolysis, [11] allylation, [18] hydrogenation [19,20] and hydrosilylation [21,22] …”

“…[ 5 , 6 , 7 , 8 , 9 , 10 , 11 ] Metal complexes, integrated within or pendant to a foldamer, can act as catalysts [11] or provide essential structural motifs,[ 12 , 13 ] including responsive centres that can alter the folded state [14] or reporters of stereochemical complexity. [ 15 , 16 , 17 ] A diverse set of reactions has been catalysed by foldamers bearing metal complexes, such as hydrolysis, [11] allylation, [18] hydrogenation[ 19 , 20 ] and hydrosilylation. [ 21 , 22 ]…”

Optimization of an Asymmetric Reaction in the Cavity of Chiral Aromatic Oligoamide Foldamers

“…In this study, we first show that diastereoselectivity of an asymmetric reaction can be implemented within the chiral cavity of aromatic oligoamide foldamers. Foldamers are synthesized by progressively coupling various aromatic amide monomers to afford considerable modularity that can be used to fine‐tune the local structure by addition, deletion, and replacement of monomers [30–32] . Compared with other self‐assembled supramolecular complexes possessing efficiency of asymmetric reactions, [33–37] the foldamers with a chiral container‐like cavity here enable modular modification to optimize the reaction, the diastereoselectivity of which could be significant increased by modifying the sequences involved in elongation (sequence 1 – 3 ) and by replacing the 7‐amino‐8‐fluoro‐2‐quinolinecarboxylic acid (Q f ) segments (sequence 8 ) at the terminus.…”