Template-Assisted Proximity for Oligomerization of Fullerenes

Comprehensive characterization of polyproline tri-helix macrocyclic nanoscaffolds for predictive ligand positioning

Multivalent ligands hold promise for enhancing avidity and selectivity to simultaneously target multimeric proteins, as well as potentially modulating receptor signaling in pharmaceutical applications. Essential for these manipulations are nanosized scaffolds that precisely control ligand display patterns, which can be achieved by using polyproline oligo-helix macrocyclic nanoscaffolds via selective binding to protein oligomers and cell surface receptors. This work focuses on synthesis and structural characterization of different-sized polyproline tri-helix macrocyclic (PP3M) scaffolds. Through combined analysis of circular dichroism (CD), small- and wide-angle X-ray scattering (SWAXS), electron spin resonance (ESR) spectroscopy, and molecular modeling, a non-coplanar tri-helix loop structure with partially crossover helix ends is elucidated. This structural model aligns well with scanning tunneling microscopy (STM) imaging. The present work enhances the precision of nanoscale organic synthesis, offering prospects for controlled ligand positioning on scaffolds. This advancement paves the way for further applications in nanomedicine through selective protein interaction, manipulation of cell surface receptor functions, and developments of more complex polyproline-based nanostructures.

Elucidating the Competitive Adsorption of H2O and CO2 in CALF-20: New Insights for Enhanced Carbon Capture Metal-Organic Frameworks

In light of the pressing need for efficient carbon capture solutions, our study investigates the simultaneous adsorption of water (H2O) and carbon dioxide (CO2) as a function of relative humidity in CALF-20, a highly scalable and stable metal-organic framework (MOF). Advanced computer simulations reveal that due to their similar interactions with the framework, H2O and CO2 molecules compete for the same binding sites, occupying similar void regions within the CALF-20 pores. This competition results in distinct thermodynamic and dynamical behaviors of H2O and CO2 molecules, depending on whether one or both guest species are present. Notably, the presence of CO2 molecules forces the H2O molecules to form more connected hydrogen-bond networks within smaller regions, slowing water reorientation dynamics and decreasing water entropy. Conversely, the presence of water speeds up the reorientation of CO2 molecules, decreases the CO2 entropy, and increases the propensity for CO2 to be adsorbed within the framework due to stronger water-mediated interactions. Due to the competition for the same void spaces, both H2O and CO2 molecules exhibit slower diffusion when molecules of the other guest species are present. These findings offer valuable strategies and insights into enhancing the differential affinity of H2O and CO2 for MOFs specifically designed for carbon capture applications.

Surface supramolecular assemblies tailored by chemical/physical and synergistic stimuli: a scanning tunneling microscopy study

Supramolecular self-assemblies formed by various non-covalent interactions can produce diverse functional networks on solid surfaces. These networks have recently attracted much interest from both fundamental and application points of view. Unlike covalent organic frameworks (COFs), the properties of the assemblies differ from each other depending on the constituent motifs. These various motifs may find diverse applications such as in crystal engineering, surface modification, and molecular electronics. Significantly, these interactions between/among the molecular tectonics are relatively weak and reversible, which makes them responsive to external stimuli. Moreover, for a liquid-solid-interface environment, the dynamic processes are amenable to in situ observation using scanning tunneling microscopy (STM). In the literature, most review articles focus on supramolecular self-assembly interactions. This review summarizes the recent literature in which stimulation sources, including chemical, physical, and their combined stimuli, cooperatively tailor supramolecular assemblies on surfaces. The appropriate design and synthesis of functional molecules that can be integrated on different surfaces permits the use of nanostructured materials and devices for bottom-up nanotechnology. Finally, we discuss synergic effect on materials science.

Synergic Effect: Temperature-Assisted Electric-Field-Induced Supramolecular Phase Transitions at the Liquid/Solid Interface

Using trimesic acid (TMA) as a model system by means of scanning tunneling microscope (STM) equipped with a temperature controller, here, we report a temperature-assisted method to cooperatively control electric-field-induced supramolecular phase transitions at the liquid/solid interface. Octanoic acid is used as a solvent due to its good solubility for TMA and its less complicated pattern formed under negative STM bias (e.g., only chicken-wire polymorphs existing). At positive substrate bias, STM revealed that TMA assembly based on temperature modulations underwent phase transitions from a porous (22 °C) to a flower (45 °C) and further to a zigzag (68 °C) structure. The transitions are ascribed to the partial deprotonation of the carboxyl groups of TMA. Both the temperature and electrical polarity of the substrate are crucial, i.e., the transitions only take place at positive substrate bias and elevated temperatures. Molecular mechanics simulations were carried out to calculate the temperature and electric field dependence of the adsorption enthalpy and free energy of the chicken-wire assembly of TMA on the two layers of graphene surface. The calculated decrease in adsorption enthalpy with the increase of temperature and electric field values that causes the TMA chicken-wire assembly to be less stable is proposed to promote the occurrence of the phase transition observed by STM. This study paves the way toward program-controlled supramolecular phase switching via the synergic effect of electrical and thermal stimuli.