Probing the work generated by the autonomous rotation around a single ruthenium atom in an organometallic complex

A variety of rotary molecular motors powered by light, chemical energy or tunnelling electrons have been synthesized and their operation in solution, in gels or on surfaces has been demonstrated. However, the single-molecule mechanics of such machines remain scarcely studied and very little data regarding their quantified performances have been disclosed. Here, we report on the synthesis of a series of molecules incorporating a five-arm rotor subunit and the direct quantitative measurement of the work generated by its rotation around the central ruthenium atom. We have used single-molecule force spectroscopy (SMFS) to detect the autonomous oscillations. We demonstrate that a mechanical load does not prevent rotation and show that the chemical nature of the arms influences the energy barrier, causing differences in the work that the motor can generate. Our results illustrate that SMFS, which is now widely used to probe processes at the scale of a few tens of nanometers in biomacromolecules, can detect motions around a single atom in a tiny synthetic molecule

Exploiting Electron Spectroscopies to Probe the Structure and Organization of Self-assembled Monolayers : a Review

In this paper, we review and discuss the use of electron spectroscopies to characterize self-assembled monolayers (SAMs). The review concentrates on thiol-derived monolayers on gold with emphasis on n-alkanethiols, considered as archetypal systems. Since they are relatively simple model systems (ease of preparation, high structural order, and flexibility in the structure of chemical groups exposed to the surface), they are particularly well-suited reference samples for molecular level understanding of surface phenomena and for disclosing the potential of surface sensitive techniques. Some examples concerning silane-derived monolayers are also discussed. Many different spectroscopic techniques have been applied to characterize SAMs. Among them, electron spectroscopies, such as XPS, UPS, photoemission with synchrotron radiation, and HREELS, have been used to investigate the structure of alkanethiols on gold, and in particular, to characterize the S–Au bond, the packing density, the crystalline order, and molecular orientation.We try here to provide an overview on the structural information that can be obtained from those techniques. Damage processes induced by X-ray and electron beam are discussed in detail