Introduction of Clutch Function into a Molecular Gear System by Silane−Silicate Interconversion

Abstract

Introduction of the clutch-declutch mechanism into a new gear system, bis(4-methyl-9-triptycyl)difluorosilane 1, is achieved by the reversible attachment of fluoride ion giving the corresponding fluorosilicate 2. Although the phase isomers of 1 (1(dl) and 1(meso)) cannot be separated because of the equilibrium via a slow gear slippage process (DeltaH(double dagger) = 17.2 +/- 0.2 kcal x mol(-1) and DeltaS(double dagger) = 0.9 +/- 0.9 cal x mol(-1) x K(-1)), 1 works as meshed molecular gears in solution at room temperature. On the other hand, silicate 2 in the solid state has quite an unusual TBP structure having two organic triptycyl groups at the apical positions and three electronegative fluorine atoms at the equatorial positions against the Muetterties rule. Rotation of the two triptycyl groups around Si-C bonds in 2 is facile and independent to each other in solution. Silicate 2 is reverted to the corresponding silane mixture by treating with excess water.

Metal-centred azaphosphatriptycene gear with a photo- and thermally driven mechanical switching function based on coordination isomerism

“…15 ). The enthalpy value is significantly lower than the reported value for covalently connected triptycene gears 15 19 .…”

“…Triptycene is a well-known part of gear molecules with a rigid, highly symmetrical paddlewheel structure. More than one triptycene rotators can be covalently connected with an organic stator designed so as to have a proper positional relationship between the connected rotators 12 13 14 15 16 17 18 19 20 21 . Another unique example of covalently linked systems is a silicon-centred bistriptycene system 19 , which undergoes switchable gearing triggered by a chemical stimulus, fluorination/defluorination.…”

“…More than one triptycene rotators can be covalently connected with an organic stator designed so as to have a proper positional relationship between the connected rotators 12 13 14 15 16 17 18 19 20 21 . Another unique example of covalently linked systems is a silicon-centred bistriptycene system 19 , which undergoes switchable gearing triggered by a chemical stimulus, fluorination/defluorination. We focused on metal ions as a control element of molecular motions due to their essential features such as reversible bonding natures with ligands, dynamic ligand exchange and external stimuli responsiveness 22 23 24 .…”

Die Evolution molekularer Maschinen

“…In den letzten zwei Jahrzehnten wurde eine Vielzahl molekularer Architekturen genutzt, um molekulare “Kolben”,35 “Kupplungen”,36 “Windmühlen”,37 “Aufzüge”,38 “Schubkarren”39 und sogar “Nano‐Autos”40 herzustellen, die vom Erscheinungsbild makroskopischer Maschinen inspiriert sind. Aber nur weil das Kalottenmodell eines Moleküls einem makroskopischen Kolben oder einem makroskopischen Auto ähnelt, muss das Molekül nicht zwangsläufig auf molekularem Niveau eine ähnliche Wirkungsweise wie diese makroskopischen Vorbilder haben.…”

Fluoride‐Controlled Molecular Brake Systems

“…In the field of supramolecular chemistry, fluoride is one of the most important recognition/detection objects and can serve in turn as a highly effective trigger for the corresponding stimulus‐responses ,. Despite prevalence, to date, reports on the utilization of fluoride for regulating the motion of machine molecules are scarce . In particular, a molecular brake system using fluoride as the regulator is unprecedented.…”