Self‐Assembling Supramolecular Hybrid Hydrogel Beads

With the goal of imposing shape and structure on supramolecular gels, we combine a low‐molecular‐weight gelator (LMWG) with the polymer gelator (PG) calcium alginate in a hybrid hydrogel. By imposing thermal and temporal control of the orthogonal gelation methods, the system either forms an extended interpenetrating network or core–shell‐structured gel beads—a rare example of a supramolecular gel formulated inside discrete gel spheres. The self‐assembled LMWG retains its unique properties within the beads, such as remediating Pd^II and reducing it in situ to yield catalytically active Pd⁰ nanoparticles. A single PdNP‐loaded gel bead can catalyse the Suzuki–Miyaura reaction, constituting a simple and easy‐to‐use reaction‐dosing form. These uniquely shaped and structured LMWG‐filled gel beads are a versatile platform technology with great potential in a range of applications.     

Self-Assembled Supramolecular Hybrid Hydrogel Beads Loaded with Silver Nanoparticles for Antimicrobial Applications

This Full Paper reports the formation of silver (Ag) NPs within spatially resolved two-component hydrogel beads, which combine a low-molecular-weight gelator (LMWG) DBS-CONHNH₂ and a polymer gelator (PG) calcium alginate. The AgNPs are formed through in situ reduction of Ag^I, with the resulting nanoparticle-loaded gels being characterised in detail. The antibacterial activity of the nanocomposite gel beads was tested against two drug-resistant bacterial strains, often associated with hospital-acquired infections: vancomycin-resistant Enterococcus faecium (VRE) and Pseudomonas aeruginosa (PA14), and the AgNP-loaded gels showed good antimicrobial properties against both types of bacteria. It is suggested that the gel bead format of these AgNP-loaded hybrid hydrogels makes them promising versatile materials for potential applications in orthopaedics or wound healing.     

Sesquiterpene Cyclizations inside the Hexameric Resorcinarene Capsule: Total Synthesis of δ‐Selinene and Mechanistic Studies

The synthesis of terpene natural products remains a challenging task due to the enormous structural diversity in this class of compounds. Synthetic catalysts are unable to reproduce the tail‐to‐head terpene cyclization of cyclase enzymes, which create this diversity from just a few simple linear terpene substrates. Recently, supramolecular structures have emerged as promising enzyme mimetics. In the present study, the hexameric resorcinarene capsule was utilized as an artificial cyclase to catalyze the cyclization of sesquiterpenes. With the cyclization reaction as the key step, the first total synthesis of the sesquiterpene natural product δ‐selinene was achieved. This represents the first total synthesis of a sesquiterpene natural product that is based on the cyclization of a linear terpene precursor inside a supramolecular catalyst. To elucidate the reaction mechanism, detailed kinetic studies and kinetic isotope measurements were performed. Surprisingly, the obtained kinetic data indicated that a rate‐limiting encapsulation step is operational in the cyclization of sesquiterpenes.     

Inducing Enantioselectivity in a Dynamic Catalyst by Supramolecular Interlocking

The design of a new class of fluxional biphenyl bisphosphinite (BIBIPHOS) ligands decorated with amino acid‐based diamide interaction sites is reported that undergo spontaneous desymmetrization. Hydrogenation of prochiral alkenes using Rh‐BIBIPHOS results in enantiomeric ratios of up to 96:4 (R/S). This stereoconvergent behavior of the fluxional BIBIPHOS ligand is triggered by pronounced intermolecular interlocking of the recognition sites, leading to the formation of a supramolecular assembly, where the axial orientation of the biphenyl ligand backbone is governed by the chirality of the amino acid moieties. Stereoinduction during catalysis is decoupled from this process and occurs as an immediate consequence of the emergent behavior of the ligands. This supramolecular system is very robust and has the potential to be adopted for other ligand designs in enantioselective catalysis.     

Cofactor Controlled Encapsulation of a Rhodium Hydroformylation Catalyst

Supramolecular approaches in transition‐metal catalysis, including catalyst encapsulation, have attracted considerable attention. Compared to enzymes, supramolecular catalysts in general are less complex. Enzyme activity is often controlled by the use of smaller cofactor molecules, which is important in order to control reactivity in complex mixtures of molecules. Interested in increasing complexity and allowing control over supramolecular catalyst formation in response to external stimuli, we designed a catalytic system that only forms an efficient supramolecular complex when a small cofactor molecule is added to the solution. This in turn affects both the activity and selectivity when applied in a hydroformylation reaction. This contribution shows that catalyst encapsulation can be controlled by the addition of a cofactor, which affects crucial catalyst properties.     

Self‐Healing,Expansion–Contraction,and Shape‐Memory Properties of a Preorganized Supramolecular Hydrogel through Host–Guest Interactions

Supramolecular materials cross‐linked between polymer chains by noncovalent bonds have the potential to provide dynamic functions that are not produced by covalently cross‐linked polymeric materials. We focused on the formation of supramolecular polymeric materials through host–guest interactions: a powerful method for the creation of nonconventional materials. We employed two different kinds of host–guest inclusion complexes of β‐cyclodextrin (βCD) with adamantane (Ad) and ferrocene (Fc) to bind polymers together to form a supramolecular hydrogel (βCD‐Ad‐Fc gel). The βCD‐Ad‐Fc gel showed self‐healing ability when damaged and responded to redox stimuli by expansion or contraction. Moreover, the βCD‐Ad‐Fc gel showed a redox‐responsive shape‐morphing effect. We thus succeeded in deriving three functions from the introduction of two kinds of functional units into a supramolecular material.     

A Competing Hydrogen Bonding Pattern to Yield a Thermo‐Thickening Supramolecular Polymer

Introduction of competing interactions in the design of a supramolecular polymer (SP) creates pathway complexity. Ester–bis‐ureas contain both a strong bis‐urea sticker that is responsible for the build‐up of long rod‐like objects by hydrogen bonding and ester groups that can interfere with this main pattern in a subtle way. Spectroscopic (FTIR and CD), calorimetric (DSC), and scattering (SANS) techniques show that such ester–bis‐ureas self‐assemble into three competing rod‐like SPs. The previously unreported low‐temperature SP is stabilized by hydrogen bonds between the interfering ester groups and the urea moieties. It also features a weak macroscopic alignment of the rods. The other structures form isotropic dispersions of rods stabilized by the more classical urea‐urea hydrogen bonding pattern. The transition from the low‐temperature structure to the next occurs reversibly by heating and is accompanied by an increase in viscosity, a rare feature for solutions in hydrocarbons.