Ke Deng

Site‐Selective Fabrication of Two‐Dimensional Fullerene Arrays by Using a Supramolecular Template at the Liquid‐Solid Interface

have been successfully used to direct theformation of ordered fullerene arrays. In this way theinterfullerene distance and symmetry of the arrangementaresolelydeterminedbythemoleculartemplateandcanbechanged by adjusting its structure. More importantly, inter-actions between fullerenes can also be modified with thisstrategy.Wehavedesignedandsynthesizedatetraacidicazoben-zene molecule NN4A (Figure1a) that exclusively formsKagomopennetworkswithtwotypesofcavitiesthathavedifferent size and symmetry at the liquid–solid interface.These cavities are capable of accommodating fullerenemolecules as guest species. Herein, we examine the siteselectivityofthenetworksfordifferentfullerenes,afeaturewhichhasnotbeenobservedforothersystemsatliquid–solidinterfaces.Azobenzenederivativesaretypicalphotochromiccompoundsthathaveawiderangeofpotentialapplications,including for optical switching, holographic storage, lightharvesting, long-term energy storage, and nonlinear opticalmaterials.

Amyloid β (1–42) Folding Multiplicity and Single-Molecule Binding Behavior Studied with STM

The fine folding and assembling characteristics of amyloid beta (Abeta) peptides are important to pharmaceutical studies of drug molecules and to the pathological analysis of neurodegenerative disorders such as Alzheimers disease at the molecular level. Here we present observations of the multiple folding characteristics of amyloid peptide Abeta(42) lamellae using scanning tunneling microscopy. Molecularly resolved core regions of Abeta(42) hairpins and unfolded peptide assembly structures are identified. The parallel assembling characteristics of Abeta(42) hairpins can be confirmed in the study. In addition, single-molecule binding characteristics of Congo red and thioflavin T have been shown to bind at the groove regions of peptide assemblies. This study demonstrates a complementary venue for studying molecular heterogeneity of peptide assemblies, as well as the binding characteristics of molecular modulators.

One plus Two: Supramolecular Coordination in a Nano-Reactor on Surface

The supramolecular coordination of zinc (II) phthalocyanine (Zn-Pc) with V-shaped bi-pyridine in a nano-reactor is probed by scanning tunneling microscopy (STM) at liquid/solid interface. Combined with density functional theory (DFT) calculations, our STM results show that the V-shaped bi-pyridine and Zn-Pc can generate stable “odd-even” patterned architectures in the TCDB network through a two-step coordination process. Moreover, great changes for the size and the shape of the host cavity have happened during the coordination process. In general, the whole coordination process is regulated by the synergies of ligand and template. To the best of our knowledge, this is the first work on imaging of supramolecular coordination in a nano-reactor. Such a template-regulated supramolecular interconversion opens a new avenue towards the crystal engineering and design as well as the generation of controllable nano-patterns.

Thermodynamic Controlled Hierarchical Assembly of Ternary Supramolecular Networks at the Liquid–Solid Interface

Building and networking: Ternary supramolecular networks have been formed by coadsorption of dissimilar ternary building units at the liquid-solid interface. The structural characteristics of the networks undergo distinctive transformations as the building units change from binary to ternary components (see graphic).

Tetrathiafulvalene-Supported Triple-Decker Phthalocyaninato Dysprosium(III) Complex: Synthesis, Properties and Surface Assembly

Self-assembly of functional compounds into a prerequisite nanostructure with desirable dimension and morphology by controlling and optimizing intermolecular interaction attracts an extensive research interest for chemists and material scientist. In this work, a new triple-decker sandwich-type lanthanide complex with phthalocyanine and redox-active Schiff base ligand including tetrathiafulvalene (TTF) units has been synthesized, and characterized by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. Interestingly, the non-centrosymmetric target complex displays a bias dependent selective adsorption on a solid surface, as observed by scanning tunneling microscopy (STM) at the single molecule level. Density function theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular assemblies, and show that such electrical field dependent selective adsorption is regulated by the interaction between the external electric field and intrinsic molecular properties. Our results suggest that this type of multi-decker complex involving TTF units shows intriguing multifunctional properties from the viewpoint of structure, electric and magnetic behaviors, and fabrication through self-assembly.

Molecular arrays formed in anisotropically rearranged supramolecular network with molecular substitutional asymmetry

We have designed two molecular building blocks, 2,6,11-tricarboxydecyloxy-3,7,10-triundecyloxy triphenylene (asym-TTT) and 2,6,10-tricarboxydecyloxy-3,7,11-triundecyloxy triphenylene (sym-TTT) with asymmetric and symmetric carboxyl groups, to construct distinct supramolecular networks. The supramolecular network of asym-TTT facilitates the formation of the directional-oriented molecular arrays of zinc phthalocyanines (ZnPc). The high-resolution scanning tunneling microscopic (STM) images as well as the density-functional theory (DFT) calculations reveal the preferential adsorption of ZnPc dimers in the anisotropic rearrangement of an asym-TTT supramolecular network. The self-repairing process of the molecular arrays after sweeping ZnPc dimers further confirms the anisotropic reconstruction of the asym-TTT network. The controlled experiments on the symmetrically substituted compound indicate the impact of the asymmetrically substituted carboxyl groups on the supramolecular networks.

Competitive adsorption and dynamics of guest molecules in 2D molecular sieves

The nanoporous network formed by 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) was used as the host nanoporous network. It has been identified that a variety of guest molecules (such as triphenylene, 1-phenyloctane and copper(II) phthalocyanine (CuPc)) can be dispersed in this template to form binary supramolecular architectures, which were studied by scanning tunneling microscopy (STM). It is interesting to observe that the host network can adjust itself in response to the molecular size and shape of the guest, and the guest molecules can be excluded by some other guest molecules. The dynamics of CuPc molecules entrapped in TCDB is reported. The STM images as well as the density-functional theory (DFT) calculations reveal that the guest selectivity depends not only on geometry of guest molecules, but also on their adsorption energy in host networks.

Molecular miscibility characteristics of self-assembled 2D molecular architectures

Various molecular networks, stabilized by hydrogen bonds or van der Waals interactions, are demonstrated in which the distribution of heterogeneous molecular species could be controlled at the level of single molecules or molecular clusters. The observed miscibility characteristics of the two-dimensional (2D) assembly structures could enable studies on the heterogeneous molecular interfaces of guest–host architectures. In addition, it could be envisioned that large cavity networks should be beneficial for studying the clustering behavior of molecular aggregates of similar or dissimilar species, chemical interactions in nanometre scale constrained areas, as well as the design of complex molecular architectures.

Visualizing Cyclic Peptide Hydration at the Single-Molecule Level

The role of water molecules in the selective transport of potassium ions across cell membranes is important. Experimental investigations of valinomycin–water interactions remain huge challenge due to the poor solubility of valinomycin in water. Herein, we removed this experimental obstacle by introducing gaseous water and valinomycin onto a Cu(111) surface to investigate the hydration of valinomycin. By combining scanning tunneling microscopy (STM) with density functional theory (DFT) calculations, we revealed that water could affect the adsorption structure of valinomycin. Hydrogen bond interactions occurred primarily at the carbonyl oxygen of valinomycin and resulted in the formation of valinomycin hydrates. The single-molecule perspective revealed in our investigation could provide new insight into the role of water on the conformation transition of valinomycin, which might provide a new molecular basis for the ion transport mechanism at the water/membrane interface.

Symmetry control of nanorod superlattice driven by a governing force

Nanoparticle self-assembly promises scalable fabrication of composite materials with unique properties, but symmetry control of assembled structures remains a challenge. By introducing a governing force in the assembly process, we develop a strategy to control assembly symmetry. As a demonstration, we realize the tetragonal superlattice of octagonal gold nanorods, breaking through the only hexagonal symmetry of the superlattice so far. Surprisingly, such sparse tetragonal superstructure exhibits much higher thermostability than its close-packed hexagonal counterpart. Multiscale modeling reveals that the governing force arises from hierarchical molecular and colloidal interactions. This force dominates the interactions involved in the assembly process and determines the superlattice symmetry, leading to the tetragonal superlattice that becomes energetically favorable over its hexagonal counterpart. This strategy might be instructive for designing assembly of various nanoparticles and may open up a new avenue for realizing diverse assembly structures with pre-engineered properties.Shape complementarity is the primary way to control the symmetry of nanoparticle assemblies. Here, the authors introduce a governing force that dominates symmetry control of nanorod superlattices, using it to obtain an unexpected and highly thermostable tetragonal lattice.