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We report a molecular investigation of a cobalt phthalocyanine (CoPc)-catalyzed CO2 reduction reaction by electrochemical scanning tunneling microscopy (ECSTM). An ordered adlayer of CoPc was prepared on Au(111). Approximately 14 % of the adsorbed species appeared with high contrast in a CO2 -purged electrolyte environment. The ECSTM experiments indicate the proportion of high-contrast species correlated with the reduction of CoII Pc (-0.2 V vs. saturated calomel electrode (SCE)). The high-contrast species is ascribed to the CoPc-CO2 complex, which is further confirmed by theoretical simulation. The sharp contrast change from CoPc-CO2 to CoPc is revealed by in situ ECSTM characterization of the reaction. Potential step experiments provide dynamic information for the initial stage of the reaction, which include the reduction of CoPc and the binding of CO2 , and the latter is the rate-limiting step. The rate constant of the formation and dissociation of CoPc-CO2 is estimated on the basis of the in situ ECSTM experiment.

We report an electrochemical scanning tunneling microscopy (ECSTM) study of the 5,10,15,20-tetraphenyl-21 H,23 H-porphyrin cobalt(II) (CoTPP) catalyzed oxygen evolution reaction (OER). A highly ordered self-assembled monolayer of CoTPP is formed on the Au(111) electrode. Cyclic voltammetry results show the OER activity of the electrode is enhanced with the increasing alkalinity of the electrolytes. The CoTPP molecules appear as two symmetric bright spots in STM images in alkaline solution, which is in sharp contrast to that in acidic solution. The molecular contour changes are attributed to the formation of the CoTPP-OH- species before OER, which is further confirmed by UV-vis absorption spectroscopy. In situ ECSTM results reveal the evolution from the CoTPP-OH- species to CoTPP molecules during OER.

Metallofullerenes have a cage-shaped molecular structure and special properties derived from encapsulated metal atoms. Owing to the ball-like fullerene cage, it is still a challenge to manipulate the metallofullerene molecule and to control its properties. Herein, we use the molecular carbon nanoring of [12]cycloparaphenylene to hoop the C80-based metallofullerene Y3N@C80 and azafullerene Y2@C79N, resulting in a stable supramolecular complex, induced molecule orientation, changed assembly behavior, and tunable spin state. These supramolecular complexes and their host–guest interactions were systematically characterized by DFT-calculations, spectroscopy, NMR, and electrochemical analysis. Scanning tunneling microscopy was employed to reveal that the metallofullerene guests dominate the assembly process on the Au(111) surface and the [12]CPP nanoring can change the weak van der Waals forces and influence self-assembly. Moreover, the electron spin in paramagnetic Y2@C79N was employed to percept the host–gues...

Metal-organic coordination structures at interfaces play an essential role in many biological and chemical systems. Understanding the molecular specificity, orientation, and spatial distribution of the coordination complexes at the nanometer scale is of great importance for effective molecular engineering of nanostructures and fabrication of functional devices with controllable properties. However, fundamental properties of such coordination systems are still rarely studied directly. In this work, we present a spectroscopic approach on the basis of tip-enhanced Raman spectroscopy (TERS) to investigate cobalt(II) tetraphenyl-porphyrine coordination species on the scale of a single molecule under ambient conditions. Coordination species anchored on gold surfaces modified with pyridine thiol self-assembled monolayers can be spectroscopically distinguished and mapped with ca. 2 nm resolution. In addition, in combination with density functional theory simulations, the adsorption configuration and molecular orientation of the coordination complexes are also revealed using TERS imaging. ISSN:0002-7863 ISSN:1520-5126

The in situ on-surface conversion process from boroxine-linked covalent organic frameworks (COFs) to boronate ester-linked COFs is triggered and catalyzed at room temperature by an electric field and monitored with scanning tunneling microscopy (STM). The adaptive behavior within the generated dynamic covalent libraries (DCLs) was revealed, providing in-depth understanding of the dynamic network switching process. ispartof: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY vol:142 issue:13 pages:5964-5968 ispartof: location:United States status: published

A pyrene-cored molecular quadripod 1,3,6,8-tetra(di(p-pyrid-4-ylphenyl)amino)pyrene (TAPyr) is presented as a noncovalent interfacial coupling reagent for the immobilization of coordination assemblies. This bench-stable molecule is readily available and has a quadripod shape with four pyridine legs and four pyridine handles on the top exterior. By a simple and short dipping procedure under ambient conditions, TAPyr is firmly immobilized on electrode surfaces in an upright fashion as probed by electrochemical, absorption spectral, atomic force microscopy, and scanning tunneling microscopy analysis. Using Pd(PhCN)2Cl2 as a metallolinker, 4-ferrocenylpyridine, a pyridine-terminated monoruthenium complex 1, and a diruthenium complex 2 with two pyridine ends have been grafted onto the ITO/TAPyr surface. The obtained thin films exhibit good electrochemical stability that is comparable or superior to those prepared by the state-of-the-art Si–O–Sn covalent functionalization. Appealing electrochromism is demonstra...

Here we show a conceptual approach to realize the scanning tunneling microscopy based induced-assembly of fullerene (C60) molecules on top of a buffer organic adlayer at room temperature in a solution environment. The realization of spatially-defined C60 assembly is attributed to the modulation of substrate-molecular interactions with the assistance of a buffer layer.

We report the potential and concentration controlled assembly of an alkyl-substituted benzo[1,2-b:4,5-b']dithiophene (DDBDT) on an Au(111) electrode by in situ electrochemical scanning tunneling microscopy (ECSTM). It is found that a lamellar structure is formed at low concentrations, while herringbone-like and rhombus structures are obtained at high concentrations. In situ STM results reveal that herringbone-like and rhombus structures could transform into lamellar structures when the electrode potential is tuned negatively. A phase diagram is obtained to illustrate the relationship and effects of concentration and substrate potential on the interfacial structures of DDBDT. Both the substrate potential and the solute concentration can modulate the self-assembly structure through changing the molecular surface density. The results provide important insights into the understanding and precise control of molecular self-assembly on solid surfaces through a combination of different approaches.

By using an oriented electric field in a scanning tunneling microscope, one can locally control the condensation of boronic acids at the liquid/solid interface. The phase transition between self-assembled molecular networks and covalent organic frameworks is controlled by changing the polarity of the applied bias. The electric-field-induced phase transformation is reversible under ambient conditions.

Here we applied ionic interactions as the driving force to fabricate well-ordered bicomponent assemblies by using two porphyrin ions equipped with oppositely-charged groups. Two kinds of bimolecular chessboard structures were successfully constructed on Au(111) and investigated by scanning tunneling microscopy (STM).

We have studied the self-assembly structure of meso-diphenyltetrathia [22]-annulene [2,1,2,1] (DPTTA) on highly oriented pyrolytic graphite (HOPG), Au(111), and single-layer graphene (SLG) modified Au(111) substrates. High resolution scanning tunneling microscopy (STM) reveals that DPTTA molecules pack into one dimensionally ordered row structure on graphene and HOPG surfaces, while assemble into two dimensional close-packed structure on Au(111) surface. We ascribe this difference to the effect of the substrate. The addition of C60 molecules on these DPTTA modified substrates further reveals that the structural difference in DPTTA adlayer can affect its ability to form donor-acceptor (D-A) hierarchical structure with C60 molecules. The results provide an example of substrate effect in self-assemblies of functional molecules, which is significant for the design of molecular based devices.

We report an in situ electrochemical scanning tunneling microscopy (ECSTM) investigation of the 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) (CoTPP)-catalyzed oxygen reduction reaction (ORR). A highly ordered CoTPP adlayer is revealed on the Au(111) electrode. High-contrast adsorbed species are monitored in CoTPP adlayer in electrolyte containing oxygen, and are attributed to the formation of CoTPP–O2 complexes. In situ STM results reveal the sharp contrast changes upon switching the substrate potential to trigger the ORR. The results benefit the understanding of the catalytic role of metal porphyrins (MPs) in the ORR, which is important for the design of MP-based catalysts.