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Pathway selection principles in reversible reaction networks such as molecular self-assembly have not been established yet, because achieving kinetic control in reversible reaction networks is more complicated than in irreversible ones. In this study, we discovered that coordination squares consisting of cis-protected dinuclear rhodium(II) corner complexes and linear ditopic ligands are assembled under kinetic control, perfectly preventing the corresponding triangles, by modulating their energy landscapes with a weak monotopic carboxylate ligand (2,6-dichlorobenzoate: dcb–) as the leaving ligand. Experimental and numerical approaches revealed the self-assembly pathway where the cyclization step to form the triangular complex is blocked by dcb–. It was also found that one of the molecular squares assembled into a dimeric structure owing to the solvophobic effect, which was characterized by nuclear magnetic resonance spectroscopy and single-crystal X-ray analysis. Achieving kinetic control over reversible self-assembly processes remains challenging. Here, the authors assemble Rh4L4 coordination squares consisting of cis-protected Rh(II) corner sites and linear ditopic ligands under kinetic control, preventing the formation of triangles by modulating the energy landscape with use of a leaving ligand. [ABSTRACT FROM AUTHOR]

Hemoproteins have recently emerged as promising biocatalysts for new-to-nature carbene transfer reactions. However, mechanistic understanding of the interplay between productive and unproductive pathways in these processes is limited. Using spectroscopic, structural, and computational methods, we investigate the mechanism of a myoglobin-catalyzed cyclopropanation reaction with diazoketones. These studies shed light on the nature and kinetics of key catalytic steps in this reaction, including the formation of an early heme-bound diazo complex intermediate, the rate-determining nature of carbene formation, and the cyclopropanation mechanism. Our analyses further reveal the existence of a complex mechanistic manifold for this reaction that includes a competing pathway resulting in the formation of an N-bound carbene adduct of the heme cofactor, which was isolated and characterized by X-ray crystallography, UV-Vis, and Mössbauer spectroscopy. This species can regenerate the active biocatalyst, constituting a non-productive, yet non-destructive detour from the main catalytic cycle. These findings offer a valuable framework for both mechanistic analysis and design of hemoprotein-catalyzed carbene transfer reactions.Hemoproteins have recently emerged as promising biocatalysts for carbene transfer reactions but mechanistic understanding of the interplay between productive and unproductive pathways in these processes is limited. Here, the authors use a combination of spectroscopic, crystallographic, and computational tools to elucidate the mechanism of a recently reported myoglobin-catalyzed cyclopropanation reaction with diazoketones. [ABSTRACT FROM AUTHOR]

Supramolecular chemistry is, broadly, the study of noncovalent interactions. Electrochemistry inherently involves supramolecular organisation of ions and solvent, so the use of supramolecular chemistry in electrochemistry has the potential for great utility in various applications. Studies of supramolecular host–guest electrochemistry have been reported for decades. In recent years, these studies have moved past investigations of basic principles and towards functional systems. This perspective will describe the main directions in which applications of functional supramolecular host–guest electrochemical systems are being developed: sensing, ion transport, and catalysis. While these research directions have shown promising results, study of supramolecular host–guest electrochemistry remains relatively rare. Challenges in the development of these systems and an outlook for future research will be outlined. [ABSTRACT FROM AUTHOR]

In biological systems, biomolecules achieve sophisticated functions based on both thermodynamic control and kinetic control. In contrast, in artificial supramolecular systems, molecular recognition behaviors in host–guest systems or self-assembly processes under thermodynamic control have been widely investigated for several decades. Recently, kinetic control of these processes has attracted more interest. This review describes three approaches for the kinetic control of supramolecular systems based on coordination chemistry. The discussion first focuses on the kinetic control of guest uptake of host–guest systems. The guest binding kinetics (i.e., guest uptake/release rate) can be basically controlled by the change in the aperture sizes of the host molecules. The second part provides representative examples of unveiling guest uptake/exchange mechanisms for a variety of supramolecular host–guest systems, which is important for the rational design of host molecules and prediction of their specific functions for future studies. The kinetic control of metal-assisted self-assembly processes is also introduced in the last part. The discussion especially focuses on investigation of the self-assembly pathway, control of the kinetic stability of self-assembled complexes, and the speed tuning of self-assembly processes by modulating the individual metal–ligand exchange rate. [ABSTRACT FROM AUTHOR]