B₁₉⁻: ein aromatischer Wankel‐Motor

Abstract

Huang et al. entdeckten vor kurzem die energetisch stabilste Struktur von B 19À (1): eine Radstruktur, bestehend aus zwei ineinandergeschachtelten ebenen aromatischen p-Systemen.[ In den letzten zehn Jahren wurden mithilfe der Computerchemie mehrere radförmige Borstrukturen vorgeschlagen, die Hauptgruppenelement- [8][9][10][11][12][13][14] oder Übergangsmetallato-me [15][16][17][18]

B13+: A Photodriven Molecular Wankel Engine

“…

Synthetic molecular motors that are capable of delivering controlled movement upon energy input are one of the key building blocks in nanomachinery. [3][4][5] These clusters are anomalously stable species of low reactivity, [3,6,7] similar to their prototypical organic aromatic congeners: benzene and coronene. The energy scale of the electronic excitation is normally two orders of magnitude larger than the molecular vibrational frequencies.

…”

“…[1] The major energy sources of molecular motors are from chemical reactions, [1a] photon beams, [1b] or electric current, [1f] which are converted into mechanical forces through the excitation of the electronic states of the molecule. [4,5] This peculiar fluxionality of B 19 À and B 13 + at room temperature has gained them the name of "molecular Wankel motors". To reduce the heat dissipation and increase the energy utilization efficiency, a motor running purely on the electronic ground-state (GS) potential energy surfaces is highly desirable.…”

“…The energy scale of the electronic excitation is normally two orders of magnitude larger than the molecular vibrational frequencies. [4,5] In equilibrium, driven by thermal fluctuations, the outerring rotation is bidirectional, and has a timescale of the order of tens of picoseconds at 300 K. To utilize B 13 + as an engine for nanomachinery, an energy source is needed to drive the molecule out of equilibrium. [2] Recently, two planar boron clusters, B 19 À and B 13 + , have been demonstrated to undergo a rare fluxional behavior: the outer ring rotates almost freely with respect to the inner ring.…”

“…[3][4][5] These clusters are anomalously stable species of low reactivity, [3,6,7] similar to their prototypical organic aromatic congeners: benzene and coronene. [2] Recently, two planar boron clusters, B 19 À and B 13 + , have been demonstrated to undergo a rare fluxional behavior: the outer ring rotates almost freely with respect to the inner ring.…”

“…[2] Recently, two planar boron clusters, B 19 À and B 13 + , have been demonstrated to undergo a rare fluxional behavior: the outer ring rotates almost freely with respect to the inner ring. [4,5] In equilibrium, driven by thermal fluctuations, the outerring rotation is bidirectional, and has a timescale of the order of tens of picoseconds at 300 K. To utilize B 13 + as an engine for nanomachinery, an energy source is needed to drive the molecule out of equilibrium. [2b,c, 3, 5, 8] The low energy barrier that made the in-plane rotation possible was due to the delocalized bonding, which rendered concentric double aromaticity of both equilibrium and transition states of the clusters.…”