On-Surface Construction of Network Structures by the <i>tert</i>-Butyl-Substituted Organic Molecules

On-surface formation of two-dimensional supramolecular network structures using molecular self-assembly has been an efficient and the most widely employed method. Through delicate modifying the molecular candidates with specific substituents, it is possible to build on-surface nanostructures according to one’s will. Here, from the interplay of high-resolution STM imaging and DFT calculations we have investigated role of the <i>tert</i>-butyl substituent in the formation of self-assembled network structures by planar aromatic molecules on metal surfaces. Our results demonstrate that the <i>tert</i>-butyl groups can change adsorption geometry of molecule from entirely flat-lying to a bit of upright-standing and vary the intermolecular interactions, which resulted in the formation of two-dimensional supramolecular network structures on both Au(111) and Ag(110). These findings further present that <i>tert</i>-butyl substituent could be a good candidate for fabricating on-surface self-assembled nanostructures from more general aromatic molecules

Exploring the Self-Assembly Behaviors of an Organic Molecule Functionalized by Terminal Alkyne and Aldehyde Groups on Au(111)

On-surface self-assembly from molecular building blocks directed by supramolecular interactions has been widely reckoned as an efficient method for controllable construction of low-dimensional nanostructures and nanomaterials. Numerous efforts have been devoted to exploring the self-assembled behaviors of molecular precursors on different surfaces and unravelling the underlying mechanism. Generally, the molecular precursors are functionalized with one kind of functional groups for directing the self-assembly. In this study, by combining real-space direct visualization and DFT calculations, we have investigated the self-assembly behaviors of an organic molecule functionalized by two different functional groups: terminal alkyne and aldehyde groups on Au(111). An ordered racemic island nanostructure is formed on Au(111), which results from the hybrid interactions between the two functional groups. Detailed DFT calculations have been performed to compare the different binding ways and binding strengths between the organic molecules

Dehalogenative Homocoupling of Terminal Alkynyl Bromides on Au(111): Incorporation of Acetylenic Scaffolding into Surface Nanostructures

On-surface C–C coupling reactions of molecular precursors with alkynyl functional groups demonstrate great potential for the controllable fabrication of low-dimensional carbon nanostructures/nanomaterials, such as carbyne, graphyne, and graphdiyne, which demand the incorporation of highly active sp-hybridized carbons. Recently, through a dehydrogenative homocoupling reaction of alkynes, the possibility was presented to fabricate surface nanostructures involving acetylenic linkages, while problems lie in the fact that different byproducts are inevitably formed when triggering the reactions at elevated temperatures. In this work, by delicately designing the molecular precursors with terminal alkynyl bromide, we introduce the dehalogenative homocoupling reactions on the surface. As a result, we successfully achieve the formation of dimer structures, one-dimensional molecular wires and two-dimensional molecular networks with acetylenic scaffoldings on an inert Au(111) surface, where the unexpected C–Au–C organometallic intermediates are also observed. This study further supplements the database of on-surface dehalogenative C–C coupling reactions, and more importantly, it provides us an alternative efficient way for incorporating the acetylenic scaffolding into low-dimensional surface nanostructures

Competition between Hydrogen Bonds and Coordination Bonds Steered by the Surface Molecular Coverage

In addition to the choices of metal atoms/molecular linkers and surfaces, several crucial parameters, including surface temperature, molecular stoichiometric ratio, electrical stimulation, concentration, and solvent effect for liquid/solid interfaces, have been demonstrated to play key roles in the formation of on-surface self-assembled supramolecular architectures. Moreover, self-assembled structural transformations frequently occur in response to a delicate control over those parameters, which, in most cases, involve either conversions from relatively weak interactions to stronger ones (e.g., hydrogen bonds to coordination bonds) or transformations between the comparable interactions (e.g., different coordination binding modes or hydrogen bonding configurations). However, intermolecular bond conversions from relatively strong coordination bonds to weak hydrogen bonds were rarely reported. Moreover, to our knowledge, a reversible conversion between hydrogen bonds and coordination bonds has not been demonstrated before. Herein, we have demonstrated a facile strategy for the regulation of stepwise intermolecular bond conversions from the metal–organic coordination bond (Cu–N) to the weak hydrogen bond (CH···N) by increasing the surface molecular coverage. From the DFT calculations we quantify that the loss in intermolecular interaction energy is compensated by the increased molecular adsorption energy at higher molecular coverage. Moreover, we achieved a reversible conversion from the weak hydrogen bond to the coordination bond by decreasing the surface molecular coverage

Formation of a G‑Quartet-Fe Complex and Modulation of Electronic and Magnetic Properties of the Fe Center

Although the G-quartet structure has been extensively investigated due to its biological importance, the formation mechanism, in particular, the necessity of metal centers, of an isolated G-quartet on solid surfaces remains ambiguous. Here, by using scanning tunneling microscopy under well-controlled ultra-high-vacuum conditions and density functional theory calculations we have been able to clarify that besides the intraquartet hydrogen bonding a metal center is mandatory for the formation of an isolated G-quartet. Furthermore, by subtly perturbing the local coordination bonding schemes within the formed G-quartet complex <i>via</i> local nanoscale scanning tunneling microscopy manipulations, we succeed in modulating the d orbitals and the accompanying magnetic properties of the metal center. Our results demonstrate the feasibility of forming an isolated G-quartet complex on a solid surface and that the strategy of modulating electronic and magnetic properties of the metal center can be extended to other related systems such as molecular spintronics

Additional file 1 of Mackinawite nanozymes as reactive oxygen species scavengers for acute kidney injury alleviation

Additional file 1: Figure S1. The release trend of hydrogen polysulfide from GFeSNs. Figure S2. Iron ions released from different concentrations of GFeSNs in PBS solution. Figure S3. AFM image of GFeSNs and the corresponding height analysis. Figure S4. •OH scavenging ratio of the GFeSNs. Figure S5. O2•− scavenging efficiency and •OH scavenging ratio of GSH. Figure S6. O2•− scavenging efficiency of GFeSNs after 24 h and 48 h in PBS. Figure S7. CAT-like activity of GFeSNs. Figure S8. Different enzyme-like activity of GFeSNs under different pH conditions. Figure S9. SEM of GFeSNs after dispersed in distilled water for 24 h, 48 h, and 96 h, respectively. Figure S10. In vitro hemolysis test of GFeSNs. Figure S11. In vivo toxicity evaluation of GFeSNs to major organs (heart, liver, spleen, lung, and kidney) 7 days and 30 days after intravenous administration. Figure S12. Serum biochemistry assay and complete blood panel data of mice intravenously injected with PBS or GFeSNs at 24 h

Bottom-Up Synthesis of Metalated Carbyne

Because of stability issues, carbyne, a one-dimensional chain of carbon atoms, has been much less investigated than other recent carbon allotropes such as graphene. Beyond that, metalation of such a linear carbon nanostructure with regularly distributed metal atoms is even more challenging. Here we report a successful on-surface synthesis of metalated carbyne chains by dehydrogenative coupling of ethyne molecules and copper atoms on a Cu(110) surface under ultrahigh-vacuum conditions. The length of the fabricated metalated carbyne chains was found to extend to the submicron scale (with the longest ones up to ∼120 nm). We expect that the herein-developed on-surface synthesis strategy for the efficient synthesis of organometallic carbon-based nanostructures will inspire more extensive experimental investigations of their physicochemical properties and explorations of their potential with respect to technological applications

Direct Formation of C–C Double-Bonded Structural Motifs by On-Surface Dehalogenative Homocoupling of <i>gem</i>-Dibromomethyl Molecules

Conductive polymers are of great importance in a variety of chemistry-related disciplines and applications. The recently developed bottom-up on-surface synthesis strategy provides us with opportunities for the fabrication of various nanostructures in a flexible and facile manner, which could be investigated by high-resolution microscopic techniques in real space. Herein, we designed and synthesized molecular precursors functionalized with benzal <i>gem</i>-dibromomethyl groups. A combination of scanning tunneling microscopy, noncontact atomic force microscopy, high-resolution synchrotron radiation photoemission spectroscopy, and density functional theory calculations demonstrated that it is feasible to achieve the direct formation of C–C double-bonded structural motifs <i>via</i> on-surface dehalogenative homocoupling reactions on the Au(111) surface. Correspondingly, we convert the sp³-hybridized state to an sp²-hybridized state of carbon atoms, <i>i</i>.<i>e</i>., from an alkyl group to an alkenyl one. Moreover, by such a bottom-up strategy, we have successfully fabricated poly­(phenylenevinylene) chains on the surface, which is anticipated to inspire further studies toward understanding the nature of conductive polymers at the atomic scale