Temperature-dependent modulation by biaryl-based monomers of the chain length and morphology of biphenyl-based supramolecular polymers

Enhanced Stability and Properties of Benzene-1,3,5-Tricarboxamide Supramolecular Copolymers through Engineered Coupled Equilibria

Improving the stability of multi-component and functional assemblies such as supramolecular copolymers without impeding their dynamicity is key for their implementation as innovative materials. Up to now, this has been achieved by a trial-and-error approach, requiring the time-consuming characterization of a series of supramolecular coassemblies. We report herein that this is possible to significantly enhance the stability of supramolecular copolymers by a minimal change in the chemical nature of one of the interacting monomers. This is achieved by replacing an ester function by an ether function in the structure of a chiral benzene-1,3,5-tricarboxamide (BTA) monomer, used as "sergeant", coassembled with achiral monomers, the "soldiers". Pseudo-phase diagrams, constructed by probing the nature of the coassemblies with multifarious analytical techniques, confirm that the greater stability of the resulting copolymers is mainly due to the minimization of competing species. This leads to better rheological and catalytic properties of the corresponding supramolecular copolymers. Favouring coassembly over undesired assembly pathways must be considered as a blueprint for the development of better-performing supramolecular multi-component systems.

Kinetic Control over Social and Narcissistic Self-Sorting from Multicomponent Mixtures in Seed-Initiated Supramolecular Polymerization by Fine-Tuning of Steric Effects

Supramolecular polymers offer an intriguing possibility to transfer molecular properties from the nano- to the mesoscale. Towards this achievement, seed-initiated supramolecular polymerization has emerged as a powerful tool, as it prevents unlimited growth and enables size control of the assembly outcome. However, the potential application of the seeding method in the context of complex supramolecular systems is hitherto unclear. Herein we demonstrate that minute differences in molecular design in direct proximity to intermolecular recognition sites govern the molecular packing and in turn dictate the efficacy of seeded polymerization processes. We introduce a stepwise increase in steric demand in the central amino acid residue of a diamide system, which gradually increases the rotational displacement within the aggregated state. This fine-tuning of the molecular packing directly affects the propensity of the different aggregates to act as seeds for the other supramolecular synthons. In turn this allows us to selectively target specific trapped monomer states in binary mixtures for social or narcissistic seeded polymerization.

Chiral versus Achiral Assemblies in Multi-Stimuli Responsive Supramolecular Polymerization of Tetra-Substituted Azobenzene Dye

Incorporating photoswitchable moieties into the molecular design of supramolecular architectures provides unique opportunities for controlling their morphology and functionality via optical stimuli. Harnessing geometrical and electrical changes in response to multiple external stimuli on the molecular level to modulate properties remains a fundamental challenge. Herein, the reversible formation of the aggregates of l-tyrosine E-azobenzene-tetracarboxamide (E-ABT) is shown to be finely controlled by light, solvent, or chemical additives. The resulting products differ not only in their overall morphology and supramolecular interactions, but also in their intrinsic chirality, that is, depending on the conditions applied, self-assembly yields chiral columns or π-stacked "achiral" oligomers. This report shows the potential of rational monomer design to achieve controlled self-assembly by stimuli of choice and paves the way toward the use of multi-responsive, sterically hindered azo-benzene aggregates in materials chemistry and nanotechnology.

Pronounced Self-Induced Diastereomeric Anisochronism in Anisidine Amino Acid Diamides

The emergent properties resulting from selective supramolecular interactions are of significant importance for materials and chemical systems. For the directed use of such properties, a fundamental understanding of the interaction mechanism and the resulting mode of function is necessary for a tailored design. The self-induced diastereomeric anisochronism effect (SIDA), which occurs in the intermolecular interaction of chiral molecules, generates unique properties such as chiral self-recognition and nonlinear effects. Here we show that anisidine amino acid diamides lead to extraordinary signal splitting in NMR spectra through supramolecular interaction and homochiral self-recognition. By systematic experiments we have investigated the underlying SIDA effect, explored its limits and finally successfully utilized it in the determination of enantiomeric ratios by NMR spectroscopy of chiral 'SIDA-inactive' compounds such as thalidomide.

Breaking Radial Dipole Symmetry in Planar Macrocycles Modulates Edge-to-Edge Packing and Disrupts Cofacial Stacking

Dipolar interactions are ever-present in supramolecular architectures, though their impact is typically revealed by making dipoles stronger. While it is also possible to assess the role of dipoles by altering their orientations by using synthetic design, doing so without altering the molecular shape is not straightforward. We have now done this by flipping one triazole unit in a rigid macrocycle, tricarb. The macrocycle is composed of three carbazoles (2 Debye) and three triazoles (5 Debye) defining an array of dipoles aligned radially but organized alternately in and out. These dipoles are believed to dictate edge-to-edge tiling and face-to-face stacking. We modified our synthesis to prepare isosteric macrocycles with the orientation of one triazole dipole rotated 40°. The new dipole orientation guides edge-to-edge contacts to reorder the stability of two surface-bound 2D polymorphs. The impact on dipole-enhanced π stacking, however, was unexpected. Our stacking model identified an unchanged set of short-range (3.4 Å) anti-parallel dipole contacts. Despite this situation, the reduction in self-association was attributed to long-range (~6.4 Å) dipolar repulsions between π-stacked macrocycles. This work highlights our ability to control the build-up and symmetry of macrocyclic skeletons by synthetic design, and the work needed to further our understanding of how dipoles control self-assembly.

Photocontrollable thermosensitive chemical spatiotemporally destabilizes mitochondrial membranes for cell fate manipulation

Perturbations in mitochondrial membrane stability lead to cytochrome c release and induce caspase-dependent apoptosis. Using synthetic smart chemicals that with changeable physicochemical properties to interfere the mitochondrial membrane stability has...