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Diarylethene derivatives are photochromic molecular switches, undergoing a ring-opening/-closing reaction by illumination with light. The symmetry of the closed form is determined by the WoodWard Hoffinann rules according to which the reaction proceeds by corirotatory rotation -in that case. Here, we show by a cOrnbined approach of scanning tunneling microscopy (STM) and density functional theory (DFT) calculations that the Open isomer of 4,4'-(4,4'-(perfluorocydopent-1-ene-1,2-diyl)bis(5-methyl-thiophent-4,2,4-dipyridine) (PDTE) retains its open form upon adsorption on a Ag(111) surface. It caribe switched into a closed form, which we identify as the digrotatOly cydization product, by controlled manipulation 'With the STM tip, Evidence of an electric-field dependent switching-process 'is interpreted on the basis of a Simple electroStatic Model, which suggests that the reaction proceedS via an "upright" intermediate state. This pathway thus strongly differs from the switching reaction in solution.
Oxide/water interfaces are ubiquitous in a wide variety of applications and the environment. Despite this ubiquity, and attendant decades of study, gaining molecular level insight into water/oxide interaction has proven challenging. In part, this challenge springs from a lack of tools to concurrently characterize changes in surface structure (i.e., water/oxide interaction from the perspective of the solid) and O-H population and local environment (i.e., water/oxide interaction from the water perspective). Here, we demonstrate the application of surface specific vibrational spectroscopy to the characterization of the interaction of the paradigmatic alpha-Al2O3(0001) surface and water. By probing both the interfacial Al-O (surface phonon) and O-H spectral response, we characterize this interaction from both perspectives. Through electronic structure calculation, we assign the interfacial Al-O response and rationalize its changes on surface dehydroxylation and reconstruction. Because our technique is all-optical and interface specific, it is equally applicable to oxide surfaces in vacuum, ambient atmospheres and at the solid/liquid interface. Application of this approach to additional alumina surfaces and other oxides thus seems likely to significantly expand our understanding of how water meets oxide surfaces and thus the wide variety of phenomena this interaction controls. (C) 2015 AIP Publishing LLC.