Two-dimensional molecular patterns were obtained by the adsorption of long-chain alkanes, alcohols, fatty acids, and a dialkylbenzene from organic solutions onto the basal plane of graphite. In situ scanning tunneling microscopy (STM) studies revealed that these molecules organize in lamellae with the extended alkyl chains oriented parallel to a lattice axis within the basal plane of graphite. The planes of the carbon skeletons, however, can be oriented either predominantly perpendicular to or predominantly parallel with the substrate surface, causing the lamellar lattice to be either in or near registry with the substrate (alkanes and alcohols) or not in registry (fatty acids and dialkylbenzenes). In the case of the alcohols and the dialkylbenzene the molecular axes are tilted by +30 degrees or -30 degrees with respect to an axis normal to the lamella boundaries, giving rise to molecularly well-defined domain boundaries. Fast STM image recording allowed the spontaneous switch between the two tilt angles to be observed in the alcohol monolayers on a time scale of a few milliseconds.

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A molecular monolayer adsorbed at the interface between the basal plane of graphite and an organic solution of didodecylbenzene has been observed in situ by scanning tunneling microscopy at a resolution of 0.2 nm. The monolayer forms a 2D polycrystal with crystallite sizes in the range of a few nanometers.The predominant domain boundary is described by a glide plane. Fast image recording allowed, for the first time, direct observation of the molecular dynamics on the time scale of 100 ms. In particular, the motion of domain boundaries could be associated with diftusing "free volume. " PACS numbers: 68.45.v, 61.16.Di, 68.55.Jk The molecular structure at the interface between a solid wall and a molecular liquid is driven by forces which are important, e.g. , for a better understanding of lubrication and adhesion, the orientation of liquid crystals through surfaces, or molecular recognition phenomena at interfaces. ' The order in a molecular monolayer is also a matter of theoretical interest, since true crystalline order cannot exist at any finite temperature in two dimensions.Experimentally, new 2D phenomena have been found for rare-gas adsorbates by synchrotron x-ray scattering ' or for small molecules like nitrogen, ethane, or hexane by neutron scattering, all adsorbed from the gas phase onto graphite.Also low-energy electron diffraction has been employed, e.g. , to the hexane layer. However, in the latter case radiation damage or organic molecules is a serious limitation. Much less is known for organic adsorbate layers at the solid-Auid interface. Part of the reason is the experimental difhculty in determining directly the structure in situ, since only a few surface-sensitive methods give atomic-scale information about the internal interface between two condensed phases.Scanning tunneling microscopy (STM) is particularly suitable for the structure determination of monolayers, provided the monolayer is su%ciently immobilized and also contributes enough to the contrast in STM. An important advantage of STM over other high-resolution electron-based surface-science tools is the fact that (1) it is a true local probe able to investigate, e.g. , only partly ordered or nanocrystalline structures, and (2) it can be operated both under ultrahigh-vacuum conditions and in various Auid ambients, thereby allowing also the study of the internal interface between a conducting solid and a Auid. One of the erst molecular layers investigated by STM was a coadsorbate of benzene and carbon monoxide on Rh(111), prepared under ultrahigh-vacuum conditions. Previous demonstrations of molecular imaging at the solid-Auid interface were on the liquid crystal noctylcyanobiphenyl ' as well as on a solution of the alkane dotriacontane on highly oriented pyrolytic graphite (HOPG), ' which both exhibit a highly ordered interfacial phase. However, so far neither packing defects nor the dynamics in the monolayers could be observed and analyzed on the molecular scale. In the present study we demonstrate that at the solid-Auid interface STM gi...

Transition-metal-catalyzed hydroformylation reactions constitute one of the most powerful tools for C-C bond formation in organic synthesis and represent an outstanding example of the application of homogeneous catalysis on an industrial scale. This process allows for the straightforward conversion of inexpensive chemical feedstock into broadly applicable aldehydes, which serve as major building blocks for numerous chemical products. These products are highly valuable for the chemical industry and used as plasticizers, detergents, and surfactants on a million ton scale. Moreover, aldehydes serve as versatile chemical intermediates for the production of fine chemicals and pharmaceuticals. Currently, most of the bulk hydroformylation processes rely on rhodium-based catalysts. The increasing demand and resulting high cost of this precious metal has resulted in alternative transition-metal catalysts becoming highly desirable. The following Review summarizes the progress achieved utilizing Ru, Ir, Pd, Pt, and Fe catalysts in hydroformylation reactions.

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