A star-shaped ruthenium complex with five ferrocenyl-terminated arms bridged by trans-platinum fragments

A decacationic ferrocene-based metallostar

Decacationic metallostars have been prepared by the reaction of permercurated ferrocene FeC₁₀(HgO₂CCF₃)₁₀ with superacidic (C₅F₅NH)(SbF₆) (pK _a = -11 estimated in H₂O) in multigram scale. In the resulting compound, [FeC₁₀Hg₁₀(NC₅F₅) _n ][SbF₆]₁₀, the labile pentafluoropyridine ligands are readily displaced by acetonitrile (MeCN) or tetrahydrothiophene (THT). In the X-ray structure of [FeC₁₀Hg₁₀(THT)₁₀][SbF₆]₁₀·24 MeCN no cation-anion contacts between mercury and fluorine were observed. Moreover, cyclic voltammetry measurements of [FeC₁₀(Hg(MeCN))₁₀]¹⁰⁺ and [FeC₁₀(Hg(THT))₁₀]¹⁰⁺ revealed a (quasi)reversible one-electron oxidation of Fe(ii) to Fe(iii). From the reaction of [FeC₁₀(Hg(MeCN))₁₀]¹⁰⁺ with MoF₆ as oxidant the ferrocenium cation [FeC₁₀(Hg(MeCN))₁₀]¹¹⁺ was obtained and characterized via single crystal XRD. These electrophilic metallostars are promising potential building blocks for the synthesis of dendritic architectures containing a robust, tenfold functionalized ferrocene core.

Elucidating the intramolecular contrast in the STM images of 2,4,6-tris(4',4'',4'''-trimethylphenyl)-1,3,5-triazine molecules recorded at room-temperature and at the liquid-solid interface

Star-shaped 2,4,6-tris(4',4'',4'''-trimethylphenyl)-1,3,5-triazine molecules self-assemble at the solid-liquid interface into a compact hexagonal nanoarchitecture on graphite. High resolution scanning tunneling microscopy (STM) images of the molecules reveal intramolecular features. Comparison of the experimental data with calculated molecular charge density contours shows that the molecular features in the STM images correspond to molecular LUMO+2.

Ferrocene-containing non-interlocked molecular machines

Ferrocene is chemically robust and readily functionalized which enables its facile incorporation into more complex molecular systems. This coupled with ferrocene's reversible redox properties and ability to function as a “molecular ball bearing” has led to the use of ferrocene as a component in wide range of non-interlocked synthetic molecular machine systems.

Synthesis of metal−organic complex arrays

The Merrifield solid-phase peptide synthesis technique has been adapted to the synthesis of homo- and heterometallic metal−organic complex arrays (MOCAs). A terpyridine-appended and Fmoc-protected L-tyrosine derivative was metalated with Pt(II), Rh(III), or Ru(II) ions in solution and sequentially coupled at the surface of functionalized polymeric resin to give a metal complex triad (Rh−Pt−Ru), tetrad (Ru−Rh−Pt−Pt), pentad (Rh−Pt−Ru−Pt−Rh), and hexad (Rh−Pt−Ru−Pt−Rh−Pt) with specific metal sequence arrangements. These were cleaved from the resin, and their character was confirmed by mass spectrometry.

Electrospray ion beam deposition: soft-landing and fragmentation of functional molecules at solid surfaces

The ion beam deposition (IBD) of rhodamine dye molecules on solid surfaces in high vacuum is explored in order to characterize the possibility of fabricating molecular coatings or nanostructures from nonvolatile molecules. Molecular ion beams with a well-defined composition are deposited on silicon oxide surfaces with a controlled kinetic energy. Photoluminescence spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS) are employed in order to characterize the sample with respect to coverage, homogeneity, and the fraction of intact landed ions (soft-landing ratio). We find that homogeneous rhodamine films of defined composition can be produced at energies of 2-100 eV. The coverage is found to be proportional to the ion dose. Soft-landing is observed for energies up to 35 eV.

A family of electron-triggered molecular motors based on aromatic building blocks

We present our strategy to control the rotation in a molecular rotary motor and the synthesis of a family of ruthenium complexes designed to perform such a task. The molecules have a piano-stool structure with a "stator" meant to be grafted on an oxide surface, and a "rotor" bearing redox-active ferrocene groups, so that addressing the molecule with nanoelectrodes would trigger rotation. The rigidity of the structure is allowed by the use of aromatic building blocks both in the stator and in the rotor fragments.

Synthesis of Molecular Motors Incorporatingpara-Phenylene-Conjugated or Bicyclo[2.2.2]octane-Insulated Electroactive Groups

The insulating role of the bicyclo[2.2.2]octane fragment has been theoretically evaluated by comparing the electronic coupling parameter (V(ab)) in 1,4-bis(ferrocenyl)benzene (1) and 1,4-bis(ferrocenyl)bicyclo[2.2.2]octane (2). The geometries were optimized by DFT and an extended Hückel calculation was performed to evaluate V(ab) by the dimer splitting method. The calculations showed a 12-fold decrease of the electronic coupling from 60 meV for 1 to 5 meV for 2. The second part describes the synthesis of two potential molecular motors with one incorporating the insulating bicyclo[2.2.2]octane fragment. These molecules are based on a ruthenium complex bearing a tripodal stator functionalized to be anchored onto surfaces. The ferrocenyl electroactive groups and the cyclopentadienyl (Cp) rotor are connected through a p-phenylene spacer (5) or through a spacer incorporating an insulating bicyclo[2.2.2]octane moiety (6).

Electron-triggered motions in technomimetic molecules

Technomimetic molecules are molecules designed to imitate macroscopic objects at the molecular level, also transposing the motions that these objects are able to undergo. This article focuses on technomimetic molecules with motions triggered by electrons. The first part is devoted to our work in the field of molecular switches: after having demonstrated the possibility of controlling an intramolecular electron transfer by photoisomerisation, we are now trying to control the isomerisation, either by electrochemistry, or by embedding the photochromic compound in a self-assembled monolayer and testing the electrical conduction with a STM tip. In a second part, we present our strategy on controlling the rotation in a molecular rotary motor and the family of ruthenium complexes designed to perform such a task. The molecules have a piano-stool structure with a "stator" meant to be grafted on an oxide surface, and a "rotor" bearing redox-active groups, so that addressing the molecule with nano-electrodes would trigger rotation. The electrical control of the charge state of a molecule by a STM tip is developed in a final part.