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Spin‐crossover compounds can be switched between two stable states with different magnetic moments, conformations, electronic, and optical properties, which opens appealing perspectives for technological applications including miniaturization down to the scale of single molecules. Although control of the spin states is crucial their direct identification is challenging in single‐molecule experiments. Here we investigate the spin‐crossover complex [Fe(HB(1,2,4‐triazol‐1‐yl)3)2] on a Cu(111) surface with scanning tunneling microscopy and density functional theory calculations. Spin crossover of single molecules in dense islands is achieved via electron injection. Spin‐flip excitations are resolved in scanning tunneling spectra in a magnetic field enabling the direct identification of the molecular spin state, and revealing the existence of magnetic anisotropy in the HS molecules. [ABSTRACT FROM AUTHOR]

Adsorption of metal‐organic complexes on metallic surfaces to produce well‐defined single site catalysts is a novel approach combining the advantages of homogeneous and heterogeneous catalysis. To avoid the "surface trans‐effect" a dome‐shaped molybdenum(0) tricarbonyl complex supported by an tolylazacalix[3](2,6)pyridine ligand is synthesized. This vacuum‐evaporable complex both activates CO and reacts with molecular oxygen (O2) to form a Mo(VI) trioxo complex which in turn is capable of catalytically mediating oxygen transfer. The molybdenum tricarbonyl‐ and trioxo complexes are investigated in the solid state, in homogeneous solution and on noble metal surfaces (Cu, Au) employing a range of spectroscopic and analytical methods. [ABSTRACT FROM AUTHOR]

The Co‐based complex [Co(H2B(pz)(pypz))2] (py=pyridine, pz=pyrazole) deposited on Ag(111) was investigated with scanning tunneling microscopy at ≈5 K. Due to a bis(tridentate) coordination sphere the molecules aggregate mainly into tetramers. Individual complexes in these tetramers undergo reversible transitions between two states with characteristic image contrasts when current is passed through them or one of their neighbors. Two molecules exhibit this bistability while the other two molecules are stable. The transition rates vary linearly with the tunneling current and exhibit an intriguing dependence on the bias voltage and its polarity. We interpret the states as being due to S=1/2 and 3/2 spin states of the Co2+ complex. The image contrast and the orders‐of‐magnitude variations of the switching yields can be tentatively understood from the calculated orbital structures of the two spin states, thus providing first insights into the mechanism of electron‐induced excited spin‐state trapping (ELIESST). [ABSTRACT FROM AUTHOR]

A set of dipolar molecular rotor compounds was designed, synthesized and adsorbed as self‐assembled 2D arrays on Ag(111) surfaces. The title molecules are constructed from three building blocks: (a) 4,8,12‐trioxatriangulene (TOTA) platforms that are known to physisorb on metal surfaces such as Au(111) and Ag(111), (b) phenyl groups attached to the central carbon atom that function as pivot joints to reduce the barrier to rotation, (c) pyridine and pyridazine units as small dipolar units on top. Theoretical calculations and scanning tunneling microscopy (STM) investigations hint at the fact that the dipoles of neighboring rotors interact through space through pairs of energetically favorable head‐to‐tail arrangements. [ABSTRACT FROM AUTHOR]

The coordination sphere of the Fe(II) terpyridine complex 1 is rigidified by fourfold interlinking of both terpyridine ligands. Profiting from an octa‐aldehyde precursor complex, the ideal dimensions of the interlinking structures are determined by reversible Schiff‐base formation, before irreversible Wittig olefination provided the rigidified complex. Reversed‐phase HPLC enables the isolation of the all‐trans isomer of the Fe(II) terpyridine complex 1, which is fully characterized. While temperature independent low‐spin states were recorded with superconducting quantum interference device (SQUID) measurements for both, the open precursor 8 and the interlinked complex 1, evidence of the increased rigidity of the ligand sphere in 1 was provided by proton T2 relaxation NMR experiments. The ligand sphere fixation in the macrocyclized complex 1 even reaches a level resisting substantial deformation upon deposition on an Au(111) surface, as demonstrated by its pristine form in a low temperature ultra‐high vacuum scanning tunneling microscope experiment. [ABSTRACT FROM AUTHOR]

The competition between honeycomb and hexagonal tiling of molecular units can lead to large honeycomb superstructures on surfaces. Such superstructures exhibit pores that may be used as 2D templates for functional guest molecules. Honeycomb superstructures of molecules that comprise a C3 symmetric platform on Au(111) and Ag(111) surfaces are presented. The superstructures cover nearly mesoscopic areas with unit cells containing up to 3000 molecules, more than an order of magnitude larger than previously reported. The unit cell size may be controlled by the coverage. A fairly general model was developed to describe the energetics of honeycomb superstructures built from C3 symmetric units. Based on three parameters that characterize two competing bonding arrangements, the model is consistent with the present experimental data and also reproduces various published results. The model identifies the relevant driving force, mostly related to geometric aspects, of the pattern formation. [ABSTRACT FROM AUTHOR]

Molybdenum( 0)- Tricarbonyl Complex Supported by anAzacalix- pyridine Ligand: Synthesis, Characterization, Surface Deposition and Conversion to a Molybdenum( VI)- Trioxo Complex with O2 [Extracted from the article]

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Atomic-scale mechanochemistry is realized from force exerted by a C60-functionalized scanning tunneling microscope tip. Two conformers of tin phthalocyanine can be prepared on coinage-metal surfaces. A transition between these conformers is induced on Cu(111) and Ag(100). Density-functional calculations reveal details of this reaction. Because of the large energy barrier of the reaction and the strong interaction of SnPc with Cu(111), the process cannot be achieved by electrical means. [ABSTRACT FROM AUTHOR]

Submono-, mono- and multilayers of the Fe(II) spin-crossover (SCO) complex [Fe(bpz)2(phen)] (bpz=dihydrobis(pyrazolyl)borate, phen=1,10-phenanthroline) have beenprepared by vacuum deposition on Au(111) substrates and investigated with near edge X-ray absorption fine structure (NEXAFS) spectroscopy and scanning tunneling microscopy (STM). As evidenced by NEXAFS, molecules of the second layer exhibit a thermal spin crossover transition, although with a more gradual characteristics than in the bulk. For mono- and submonolayers of [Fe(bpz)2(phen)] deposited on Au(111) substrates at room temperature both NEXAFS and STM indicate a dissociation of [Fe(bpz)2(phen)] on Au(111) into four-coordinate complexes, [Fe(bpz)2], and phen molecules. Keeping the gold substrate at elevated temperatures ordered monolayers of intact molecules of [Fe(bpz)2(phen)] are formed which can be spin-switched by electron-induced excited spin-state trapping (ELIESST). [ABSTRACT FROM AUTHOR]

The conductance, frequency shift, and energy dissipation are measured during the formation of a contact to a single tin-phthalocyanine (SnPc) molecule. The molecule is located on top of a first SnPc layer on Ag(111). The data show that subtle changes of the adsorption geometry cause drastic differences of the conductance, force, and dissipation signals. Site-dependent averaged conductance shift versus piezo displacement. [ABSTRACT FROM AUTHOR]

An asymmetric turn: Scanning tunneling spectroscopy has been used to analyze the structure of tris[4‐(phenylazo)phenyl)]amine on a Au(111) surface. A degenerate marker state serves as a sensitive probe for the structure of the adsorbed molecules. [ABSTRACT FROM AUTHOR]

Copyright of Chemie in unserer Zeit is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Adsorption of metal‐organic complexes on metallic surfaces to produce well‐defined single site catalysts is a novel approach combining the advantages of homogeneous and heterogeneous catalysis. To avoid the "surface trans‐effect" a dome‐shaped molybdenum(0) tricarbonyl complex supported by an tolylazacalix[3](2,6)pyridine ligand is synthesized. This vacuum‐evaporable complex both activates CO and reacts with molecular oxygen (O2) to form a Mo(VI) trioxo complex which in turn is capable of catalytically mediating oxygen transfer. The molybdenum tricarbonyl‐ and trioxo complexes are investigated in the solid state, in homogeneous solution and on noble metal surfaces (Cu, Au) employing a range of spectroscopic and analytical methods. [ABSTRACT FROM AUTHOR]