There is considerable ongoing interest in understanding the electrical properties of single molecules both from a fundamental point of view and for potential applications in singlemolecule technologies. [1][2][3][4] An important goal in molecular electronics is the ability to switch, by means of electrochemical gating, the conductance through a single molecule and, in this context, the anthraquinone/hydroanthraquinone, AQ/H 2 AQ, redox couple has been proposed as a suitable candidate for study. [5] Indeed, calculations [6] predict that electrochemical gating of conductance in AQ-based molecular switches should be strong, with conductance on(H 2 AQ)/ off(AQ) ratios of several orders of magnitude. The switching mechanism is due to the presence of destructive quantum interference (QI) between various conductance channels in the cross-conjugated AQ, which is absent in the linearconjugated H 2 AQ, thereby resulting in lower conductance in AQ, compared to H 2 AQ. Recently, Fracasso et al. [7] have experimentally confirmed the operation of QI in bulk conductance studies of self-assembled monolayers (SAMs) of arylethynylene thiolates (aryl = anthracene, AQ, 9,10dihydroanthracene). [7] We now report the first experimental evidence for the operation of electrochemically controlled QI in a novel AQbased norbornylogous bridge tetrathiol, 5AQ5 (Scheme 1), from single-molecule conductance measurements using the scanning tunneling microscopy (STM) break junction technique. [8] We show that the AQ moiety in 5AQ5 can be electrochemically and reversibly switched in situ between the high-conducting H 2 AQ form and the low-conducting AQ system. Further, we demonstrate that the potential range of the conductance enhancement can be shifted using different pH values. This pH dependency of the AQ/H 2 AQ redox reaction constitutes an extra degree of freedom that can control single-molecule conductivity.A key design feature of 5AQ5 is the cementing of the AQ group into a rigid, structurally well-defined norbornylogous (NB) unit bearing two pairs of thiol groups at each end, thereby conferring additional stability to SAMs derived therefrom. The 19.8 length of 5AQ5 is much greater than the gate thickness, that is, the electrochemical double layer that relates to the diameter of the ions used in the electrolyte, thereby ensuring that the field screening effect due to the proximity of the source and drain electrodes is negligible. [9] Norbornylogous bridges have played pivotal roles in investigating many fundamental aspects of electron-transfer (ET) processes, [10,11] including those involving SAMs derived therefrom. [12][13][14][15][16] In particular, NB bridges are very efficient mediators of ET by the superexchange mechanism and it was hoped that the NB bridge would likewise facilitate coherent charge transport in 5AQ5, which is a prerequisite for QI to be operative. This issue was first investigated by determining the magnitude and distance dependence of the single-molecule conductivity in 5AQ5 and its longer cognate, 8AQ8. X-ray photoele...

Herein, we describe the synthesis of straight (S) and L-shaped (L) norbornylogous bridges (NBs) with an anthraquinone moiety at the distal end as the redox-active head group and two thiol feet at the proximal end, by which the molecules assemble on gold surfaces. The NB molecules were shown to form self-assembled monolayers (SAMs) with a well-behaved surface redox process. The SAMs were characterized by using in situ IR spectroscopy, cyclic voltammetry, scanning tunnelling microscopy and electrochemical impedance spectroscopy. The surface selection rules associated with the IR band intensities allowed the estimation of the position of the anthraquinone moiety with respect to the surface and the tilt of the bridge with respect to the surface normal, both in pure and diluted monolayers. It is shown that the S- and L-NBs hold the plane of the anthraquinone moiety close to the surface normal or the surface tangent, respectively. Neither NB molecule changes its orientation if spaced by diluents on the surface. The difference in the structure of the S- and L-NB SAMs provides a suitable framework for the investigation of factors that govern electron transfer of anthraquinone moieties across self-assembled monolayers with limited structural ambiguity, as compared with the commonly used structurally flexible alkanethiol monolayers.

A new class of electroactive norbornylogous bridges, with no net curvature, that form self-assembled monolayers on gold electrodes were studied by electrochemistry and in situ infrared spectroscopy. The influence of the electrode potential on the structure and conformation of the self-assembled monolayers (SAMs) was investigated. This was performed using two different lengths of rigid norbornylogous bridges with terminal ferrocene moieties and ω-hydroxyalkanethiols. It was found that single component monolayers of the rigid norbornylogous bridges changed their tilt angle with their transition from the ferrocene to ferricinium. However, when the norbornylogous SAMs were diluted with ω-hydroxyalkanethiols the tilt angle remained unchanged upon oxidation of ferrocene to ferricinium. It was also observed that the tilt angle of the diluent, ω-hydroxyalkanethiols changed at potentials exceeding 500 mV.

JJG and MN-PR thank the Australian research council for support. Dr. Erwann Luais is acknowledged for the XPS experiments. Dr. Mohan Bhadbhade and Australian Synchrotron are acknowledged for their technical support.

Three large earthquakes hit japan in the last few years continuously. It affected country's economy and hard to recover specially the manufacturing sector. For avoiding such impacts in the future, lessons were studied and actions were taken. This study therefore was conducted to assess the basic minimum machine tool motion behavior criteria by utilizing the existing seismic data. Particularly, the japan real earthquake data (The 2004 chūetsu and the great hanshin earthquakes as well as the 2011 Tūhoku earthquake) and mathematical models that mimic the movement of machine tools with screw jack mounting during seismic occurrence were considered and developed. For the validity, both mathematical analysis and experimental performances of a previously developed small mock-up structure of a machine tool were conducted. The study concludes that (1) the possible motion behavior of a machine tool was able to be defined and calculated; (2) using the existing real seismic data able to predict the motion behaviour of a machine tool; and (3) it was observed that up-to approximately 60 % accuracy obtained when using the real earthquake data and the developed mathematical models for analysing machine tool motion behavior.