Electron Attachment Leads to Unidirectional In-Plane Molecular Rotation of Para-Chlorostyrene on Si(100)

Abstract

We report the observation of electron-induced unidirectional planar molecular rotation of para-chlorostyrene on Si(100), studied by scanning tunneling microscopy (STM) at room temperature and by ab initio theory. This bifunctional molecule is shown to be favorable to the electroninduced rotation since the phenyl group acts as a pivot and the vinyl as a lever arm. In the initial configuration, both phenyl and vinyl are attached to silicon dimers along the same row of the substrate. The first electron from the STM tip is observed to induce a lateral shift of the vinyl to "state 1" in which the vinyl is bound asymmetrically to one side of a silicon dimer. The second electron is found to give rise to a ∼60°rotation to "state 2", a configuration in which the vinyl has swung around the phenyl to an adjacent dimer row. The impulsive two-state (I2S) model was employed to explain the conversion of the initial state to state 1 and the conversion of state 1 to state 2. These two successive impulses were computed by the I2S model to be the result of excitation to different configurations in an anionic excited state. Following addition of the second electron, the repulsion between the asymmetric vinyl and the surface was shown to give rise to a torque with the magnitude and direction required to explain the observed rotation.

Adsorption of Acetonitrile on Si(111)-(7 × 7)

“…The technologically most important material, silicon (Si), plays ubiquitous and irreplaceable roles in the development of micro- and optoelectronic devices and so on. Studies on the surface chemistry of silicon have received much attention from the viewpoint of basic science. − Many previous reports in this area have focused primarily on the binding of molecules comprising unpolarized CC or CC, − five-membered aromatics, − benzene and its derivatives, − and some other unsaturated cyclic hydrocarbons on pure Si surfaces. , These molecules can be adsorbed on Si(100) via [2 + 2] or/and [4 + 2] cycloaddition reactions. Turning our eyes to the polarized molecules, the adsorption behavior of organic molecules with the cyano group (CN), for example, the simplest nitrile of acetonitrile (CH 3 CN), has been also investigated on Si(100). − Several experimental , and theoretical ,− studies suggested a [2 + 2] cycloaddition reaction via the CN group (di-σ model).…”

Patterns of Reacted Adatoms in Adsorption of Acetonitrile on Si{111}-(7 × 7)

“…Studies on silicon-based surface chemistry have attracted a lot of attention from the perspective of basic science. − A lot of research works have been performed for the molecular adsorption on Si surfaces, − where the various types of molecules, from simple to complex ones, are used for exploring new functions of surfaces. Several works have concerned mainly on the molecules with unpolarized CC or CC, − multiple-membered aromatics, − ,, some unsaturated cyclic hydrocarbons, ,, zwitterionic organic molecules, , and benzene and its related molecules. − ,,− The adsorption behavior of polarized molecules with CN function, the simplest nitrile of acetonitrile, was reported on Si{100}. − For acetonitrile, it was suggested in several experimental , and theoretical ,− works that a [2 + 2] cycloaddition reaction through the CN function occurred (di-σ model). The acetonitrile adsorbed molecularly on Si{100} in a di-σ configuration, holding a CN functionality, followed by further multiple reactions. − …”