Toward Coordination Cages with Hybrid Chirality: Amino Acid-Induced Chirality on Metal Centers.

Tripodal chiral ligands containing amino acid residues and salicyl-acylhydrazone units were synthesized and used to obtain coordination cages through deprotonation and coordination to gallium. These coordination cages have GaL stoichiometry and pinwheel geometry with two types of chiral centers built into their walls: stereogenic centers at the amino acid backbones and stereoselectively induced centers at metal ions. The pinwheel geometry is unique among analogous cages and originates from the partial flexibility of the ligands.

Amplification of Electronic Circular Dichroism-A Tool to Follow Self-Assembly of Chiral Molecular Capsules.

Electronic circular dichroism (ECD) can be used to study various aspects of self-assembly (definition of stoichiometric ratios, chirality amplification during self-assembly, host-guest complexation). In this work, we show that ECD is a valuable tool for monitoring the self-assembly of chiral peptide-based capsules. By analyzing the signs, intensities, and temperature dependences of ECD bands, the effects of the non-specific processes can be separated from the restriction of intramolecular motion (RIM) caused by discrete self-assembly.

Enaminone Substituted Resorcin[4]arene-Sealing of an Upper-Rim with a Directional System of Hydrogen-Bonds.

The paper presents the synthesis of an enaminone resorcin[]arene via a thermally activated -quinomethide. The crystal structure indicates that in the solid state all enaminone units participate in a unidirectional seam of 12 intramolecular hydrogen bonds that are formed around the cavity. The molecule exhibits symmetry, with two opposite-laying enaminone units directed inside the cavity (""), and the other two units outside the cavity ("").

Self-Assembly and Ordering of Peptide-Based Cavitands in Water and DMSO: The Power of Hydrophobic Effects Combined with Neutral Hydrogen Bonds.

Directional self-assembly of uncharged molecules in water is a major challenge in supramolecular chemistry. Herein, it is demonstrated that peptide-based cavitands wrap around a hydrophobic core (fullerene C ) by a combination of the hydrophobic effect and hydrogen-bonding interactions to form highly ordered three-component complexes in water that resemble the molten-globule stage of protein folding. The complexes were characterized by DOSY NMR spectroscopy, small-angle X-ray scattering, and circular dichroism, and their structures were confirmed by X-ray crystallography.

Inherently chiral iminoresorcinarenes through regioselective unidirectional tautomerization.

Tetraformylresorcin[4]arene is obtained in 48% yield via a chromatography-free Duff reaction. The formylated resorcinarene reacts easily with primary aliphatic and aromatic amines. The resulting imines exist exclusively in keto-enamine forms.