Scorpionate Hydrotris(indazolyl)borate Ligands as Tripodal Platforms for Surface‐Mounted Molecular Gears and Motors

Abstract

This microreview describes the use of scorpionate hydrotris(indazolyl)borate ligands to build structurally rigid bifunctional surface-mounted molecular gears or motors. The article starts with the synthesis of 6-functionalized indazoles and their corresponding scorpionate tris(indazolyl)borate tripodal ligands. Thioether groups allow the tripodal anchoring of such ligands on metallic surfaces, whereas ester functions enable an- [a] Scheme 1. Synthesis of poly(pyrazolyl)borates. To compensate for the gradual decrease in reactivity of the functionalized borohydride, increasing the reaction temperature allows further substitution of the boron atom. 2216Scheme 3. Jacobson indazole synthesis by acetylation, nitrosation, and cyclization of an o-toluidine derivative (R stands for any electron-donating or electron-withdrawing group).Scheme 7. Synthesis of potassium tris{6-[(ethylsulfanyl)methyl]indazol-1-yl}hydroborate.

Modular synthesis of pentaarylcyclopentadienyl Ru-based molecular machines via sequential Pd-catalysed cross couplings

“…Such key intermediates may be engaged in various transition metal-catalysed cross-coupling reactions to yield target molecules with high structural diversity, as reported for the synthesis of diverse molecular motors and gears. 10 However, in contrast to previous work leading to symmetrical cyclopentadienyl platforms through five-fold cross-couplings, discrimination of one position out of five is now required.…”

Desymmetrised pentaporphyrinic gears mounted on metallo-organic anchors

“…This scorpionate ligand lifts away from the surface the ruthenium rotation axis and thus the rotor, while affording tight anchoring on noble metal surfaces at low temperature. 34 It is important to note here that translation of such complexes by STM lateral manipulation is still possible at 77 K while diffusion is totally frozen at 4 K, which allows a dedicated spatial molecular arrangement to be set up by STM manipulation and subsequently frozen. This ruthenium-based scaffold seemed particularly well adapted for the construction of trains of molecular gears on surfaces, with control over the rotation axis orientation, the intermolecular distance and the height of the cogwheels, decoupled from the surface.…”

Mechanics of Molecule-Gears with Six Long Teeth

“…11 Also multistep chemical synthesis now allows chemists to prepare a wide range of tailor-made molecule-gears with various shapes and structures. 18 In particular, it is possible to synthesize metallo-organic structures to be deposited on surface, incorporating a top rotor linked to a central single metal atom rotation axle, itself supported by an additional ligand.…”