Fine‐Tuning of Chiral Microenvironments within Triple‐Stranded Helicates for Enhanced Enantioselectivity

Abstract

Here we report the formation of an unexpected and unique family of chiral helicates.C rystal structures showt hat these triple-stranded Zn II 2 L 3 complexes are held together by subcomponent assembly of axially chiral diamine-functionalized 1,1'-biphenol ditopic with 2-formylpyridine and Zn II . Specifically,t he molecular helicity of the complexes can be controlled by the absolute configurations of the bimetallic vertices,which has been shown to be homoconfiguration (DD) or mesomeric configuration (DL), depending critically on the bulky groups and length of the spacers.F ascinatingly,i nt his system we can engineer the space-restricted chiral microenvironments with varied polar and apolar moieties,w hich profoundly influence the binding affinities and chiral discrimination properties of the helicates,l eading to highly enantioand helix-sense-selective recognition for chiral amino alcohols (up to 9.35). This work reveals the transformation of singlemolecule chirality to global supramolecular chirality within well-defined helicates and demonstrates that their chiral discrimination are highly dependent on the superior microenvironments.

Axially Chiral Dodecanuclear Lanthanide Clusters Constructed by “Bottom‐Up” Self‐assembly for Enantioselective Sensing

“…[ 27 ] For each substrate molecule in this work, the binding energy of ( S )‐enantiomer may be numerically greater than that of ( R )‐enantiomer, indicating stronger binding affinity between ( S )‐enantiomer and R‐2 . [ 34‐35 ] As a consequence, the fluorescence quenching efficiency caused by the addition of ( S )‐enantiomer in R‐2 is greater than that of the addition of ( R )‐enantiomer, resulting in chiral discrimination between two enantiomers.…”

“…Axial chirality, which is different from the central chiral molecules, usually comes from restrained rotation around the aryl‐aryl bonds, and represents a special stereoisomeric mode. [ 1‐2 ] Axially chiral molecules have received extensive attention because of their important applications, such as asymmetric catalysis, [ 3 ] chiral recognition [ 4 ] and chiral separation. [ 5 ] Therefore, more and more chemists have used axial chiral molecules to synthesize chiral metal clusters in recent years.…”

Fine‐Tuning of Chiral Microenvironments within Triple‐Stranded Helicates for Enhanced Enantioselectivity

“…However,t he g abs value of H-2 (5.1 10 À3 )e xhibit smaller than L 2 (9.4 10 À3 ), which may be attributed to the reduction of molecular helicity through its mesomeric configuration . Single-crystalX -ray structure of DL-H-2 (Fe) [29] (a) and its space filling model (b). c,d) The handedness of two Zn II centers shows mesomeric configuration (DL).…”

“…Figure 4. Single-crystalX -ray structure of DL-H-2 (Fe)[29] (a) and its space filling model (b). c,d) The handedness of two Zn II centers shows mesomeric configuration (DL).…”

Synthesis and multifunctional sensing ability of axially chiral tetranuclear europium clusters

“…It has broad application potential in catalysis, recognition, and chiral resolution. 21,27,28 However, the large stereospecific hindrance makes it difficult to control the synthesis of metal clusters by axial chiral ligands. 8,29–31 Therefore, the construction of functional axial chiral metal clusters remains a challenge in synthetic chemistry.…”