Solvent-Dependent Core-Modified Rubyrin Self-Assembly at Liquid/Solid Interfaces

Tailoring the pore size of expanded porphyrinoids for lanthanide selectivity

Despite increase in demand, capacity for the recycling of rare earth elements remains limited, partly due to the inefficiencies with processes currently utilised in the separation of lanthanides. This study highlights the potential use of expanded porphyrinoids in lanthanide separation through selective binding, dependent on the tailored pore size of the macrocycle. Each emerging trend is subjected to multi-factored analysis to decompose the underlying source. Results promote the viability of size-based separation with preferential binding of larger lanthanum(iii) ions to amethyrin and isoamethyrin macrocycles, while smaller macrocycles such as pentaphyrin(0.0.0.0.0) present a preferential binding of lutetium(iii) ions. Additionally, the porphyrin(2.2.2.2) macrocycle shows a selectivity for gadolinium(iii) ions over both larger and smaller ions. An upper limit of applicable pore size is shown to be ≈2.8 Å, beyond which the formed complexes are predicted to be less stable than the corresponding nitrate complexes.

Two-dimensional molecular networks at the solid/liquid interface and the role of alkyl chains in their building blocks

Nanoarchitectonics has attracted increasing attention owing to its potential applications in nanomachines, nanoelectronics, catalysis, and nanopatterning, which can contribute to overcoming global problems related to energy and environment, among others. However, the fabrication of ordered nanoarchitectures remains a challenge, even in two dimensions. Therefore, a deeper understanding of the self-assembly processes and substantial factors for building ordered structures is critical for tailoring flexible and desirable nanoarchitectures. Scanning tunneling microscopy is a powerful tool for revealing the molecular conformations, arrangements, and orientations of two-dimensional (2D) networks on surfaces. The fabrication of 2D assemblies involves non-covalent interactions that play a significant role in the molecular arrangement and orientation. Among the non-covalent interactions, dispersion interactions that derive from alkyl chain units are believed to be weak. However, alkyl chains play an important role in the adsorption onto substrates, as well as in the in-plane intermolecular interactions. In this review, we focus on the role of alkyl chains in the formation of ordered 2D assemblies at the solid/liquid interface. The alkyl chain effects on the 2D assemblies are introduced together with examples documented in the past decades.

Accelerating electrochemically catalyzed nitrogen reductions using metalloporphyrin-mediated metal-nitrogen-doped carbon (M-N-C) catalysts

Herein, a series of transition metal coordinated metalloporphyrin-mediated M-N-C catalysts with single and dual metal atoms were prepared and characterized. Interestingly, these M-N-C catalysts exhibit accelerated N₂ reduction behaviors through electrochemical catalysis. At the potential of E = -0.4V (vs. RHE), the optimum catalyst Fe_0.95Ni_0.05TPP@rGO-800 shows excellent catalytic activity, and the NH₃ yield is 22.5 μg mg_cat^-1 h^-1, which is much higher than that of its single metal counterparts alone, and the faradaic efficiency is as high as 50.7%, which is better than those of most reported catalysts. These results provide an opportunity to further explore the efficient electrochemical synthesis of NH₃ from M-N-C materials in the future.

Odd-Even Effect on Supramolecular Co-Assemblies: Control over the Two-Dimensional Self-Assemblies of a Fluorenone Derivative with Asymmetrically Substituted Alkyl Chains

The precise control of two-dimensional supramolecular co-assemblies presents a research topic related to advance nanotechnology. Here, we report a scanning tunneling microscopy (STM) study of the mixture behavior of three fluorenone derivatives at the liquid-solid interface. The target molecule is F-C₁₂C₁₃ whose structure bears asymmetrical alkyls, whereas the regulating molecules, either F-C₁₂C₁₂ or F-C₁₃C₁₃, are structurally symmetric. By STM imaging of systematic mixtures with various volumes among the sample solutions, we found that the mixing ratio mainly determined the binary outcomes. Compared with F-C₁₂C₁₂, F-C₁₃C₁₃ shows a stronger ability to dominate the patterning, explained by the larger binding and adsorption energies calculated by the force field simulations. Moreover, the odd-even effect exists in the system. Overall, we acquired knowledge about the regulating ability of bi-component supramolecular assembling, especially for structurally asymmetric molecular systems.

Conformationally Distinct [26]Heterorubyrin(1.1.0.1.1.0) Macrocycles and Their Bis-BODIPYs: Synthesis, Structure, and Optical Properties

Two conformationally different [26]rubyrin(1.1.0.1.1.0) macrocycles with varying heteroatoms (S/O) and their bis-BODIPYs are reported. The solid-state structure confirms O₂N₄ with fairly planar pyrrole-inverted conformation, whereas a thiophene-inverted structure for S₂N₄ is observed. Such conformational differences can also be clearly realized from their spectral and optical features. Upon BF₂ complexation, both rubyrins led to their respective bis-BODIPYs where S₂N₄-BOD displayed a perfectly planar conformation as evident from its X-ray structure.

π-Conjugated Macrocycle Host-Guest Coassembly with C60 on HOPG

Two kinds of π-conjugated macrocycles with aggregation-induced emission (AIE) properties were investigated by scanning tunneling microscopy (STM) to elucidate their self-assembly behaviors and interaction with C60 on a highly oriented pyrolytic graphite (HOPG) surface. Both TPEMC and TPEMCS could self-assemble into orderly cavity structures. However, C60 guest molecules could only successfully enter the cavity of TPEMC to form a stable TPEMC + C60 host-guest coassembly structure. Density functional theory (DFT) calculations were also used to interpret the assembly mechanisms. This work disclosed the assembly characteristic of these new types of conjugated macrocyclic compounds, which was helpful to develop new structural porous luminescent materials.

On-Surface Self-Assembled Structural Transformation Induced by Schiff Base Reaction and Hydrogen bonds

By utilizing scanning tunneling microscopy (STM), the self-assembled nanostructures of three characteristic aldehydes have been examined at the solution-solid interface. By introducing the active reactant 5-aminoisophthalic acid (5-AIPA), we succeeded in changing the self-assembled molecular structures through the condensation reaction and obtained the information on structural transformation in real time. The corresponding carboxyl conjugated derivatives were formed in situ and developed into the closely packed and ordered molecular architectures via hydrogen bonds at the solution-solid surface. The relevant simulations have been utilized to interpret the mechanisms of forming the nanostructures. The corresponding theoretical calculation is used to explain the reaction mechanism. Compared with the traditional ways, the on-surface condensation reaction in situ could not only provide a more convenient method for regulating the self-assembled architectures but also offer a promising strategy for building functional nanostructures and devices.

Progress in the self-assembly of porphyrin derivatives on surfaces: STM reveals

The latest progress in the assembly of porphyrin derivatives on solid surfaces.

Modulation of the optical properties of chiral porphyrin dimers by introducing bridged chiral amide-bonds

The d/l-enantiomers of a series of three Zn(II)tetraarylporphyrin dimers were synthesized and isolated by incorporating a bridging amide-bonded xanthene moiety at the para-position of one of the meso-aryl rings. The electronic structures and optical properties were modulated by incorporating chiral amino acid moieties into the amide-bonding moieties of the xanthene bridge that contain methyl, tolyl and 2-methylindole substituents. A cofacial dimer was formed in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) resulting in a significant red shift of the B band, due to a relative destabilization of the HOMO, which has large MO coefficients on the pyrrole nitrogens. The sign sequences observed in the B band region of the CD spectra due to the presence of the chiral amino acid moieties were modified due to this change in geometry. Significant CD intensity is also observed in the B band region of the CD spectra of anion radical species during in situ spectroelectrochemical measurements.

Solvent-Dependent Self-Assemblies and Pyridine Modulation of a Porphyrin Molecule at Liquid/Solid Interfaces

On the highly oriented pyrolytic graphite (HOPG) surface, a new porphyrin molecule MT-4 containing a porphine core with six alkyl chains and two carboxyl groups has been explored using scanning tunneling microscopy (STM) technology. Solvent and pyridine regulation have been proved to be two effective ways to control and tune the supramolecular structure of MT-4 at interfaces. Different high-resolution STM (HR-STM) images with highly ordered and closely packed arrangements were gained at the corresponding liquid-solid interface, including phenyl octane (PO), 1-heptanoic acid (HA), and 1-hexanol. Except for the solvent effect, introducing pyridine derivatives such as 4,4'-vinylenedipyridine (DPE) and 4,4'-((1E,1'E)-(2,5-bis(octyloxy)-1,4-phenylene) bis(ethene-2,1-diyl)) dipyridine (PEBP-C8) is also effective to modulate the self-assembly of MT-4. With careful analysis of the STM pictures and the density functional theory (DFT) computational exploration, we figured out the molecular model, interaction energies, and self-assembly mechanism of each system at the interface. This work provides a simple and effective approach for quickly building diverse nanoarchitectures by utilizing different noncovalent interactions. Meanwhile, it would give a perspective to regulate and control self-assembly arrays for devising novel molecular-based materials through more optimal strategies.