Two new tripodal ligands designed to anchor complexes onto surfaces have been synthesized. They integrate ester or thioether functions at the 6-position of the indazoles. Potassium hydrotris [6-(ethoxycarbonyl)indazolyl] borate and potassium hydrotris{6-[(ethylsulfanyl)methyl]indazolyl}borate exhibit three pendant groups oriented to anchor complexes onto an oxide and a metallic surface, respectively. Their complexation with [RuCp(CH3CN)(3)]PF6 yielded two piano-stool-shaped complexes that were characterized by X-ray diffraction. Comparison with the synthesized unfunctionalized analog showed that the three 6-substituted functions do not interfere with the coordination site and are particularly well oriented for surface deposition. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).

A series of tridentate ligands N,N-bis-[(di-substituted-1-pyrazolyl)methyl]arylamines 2–3a,b and benzylamine 4a,b, tetradentate N,N′-bis-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 7a,b and hexadentate N,N,N′,N′-tetra-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 8a,b has been prepared in good yield by condensation of arylamines, benzylamine or para-phenylenediamine with N-hydroxymethyl disubstituted pyrazoles 1a,b. The synthesis and characterisation of these various polydentate ligands are described.

A mono-molecular machine is a molecule designed to perform a function providing energy, data and/or orders to the molecule. A 'monumentalization' approach ( the synthesis of very large molecules) is used to synthesize technomimetic molecules, i.e. molecules able to transpose macroscopic objects and their motions at the molecular level, and grants access to the study of the mechanical properties of a single molecule. This paper focuses on the mechanical molecular machines developed in our group which are controlled one at a time by the tip of a scanning tunnelling microscope, like the molecular wheelbarrow and the molecular gear, or in the future by an atomic force microscope, as in the case of the molecular motor.

The paper describes several realizations and experiments based on a "single molecule". Chemical synthesis yields highly elaborated molecules which can be deposited on a suitable surface, so that basic processes can be studied: electron transport, switching, amplification, mechanical actions. The precise control of the molecule/metal connection is of utmost importance. The main tool is here the scanning tunnelling microscope, allowing in a first step the identification and observation of the molecule (including its conformation), and in a second step, the study of the properties of this single object.

ABSTRACT Dithienylethylene unit have been incorporated in a molecular wire. Incorporated in a Self Assembled Monolayer and tested by Scanning Tunnelling Microscopy, the molecule has been shown to have a blinking contrast. Redox properties of model compounds have been explored in order to explain this feature: all molecules can be oxidized and the resulting radical cations may undergo ring closure or opening depending on its substituents.

The design and synthesis of a ruthenium complex are described, together with its physico-chemical properties, showing its potential to work as a single molecule rotary motor.

New ruthenium(II) complexes with cyanamide ligands, cis-[Ru(bPY) (2)(lpcyd)(2)] (1) and [Ru(bPY)(2)(OHpcyd)(2)] (2) (bpy = 2,2'-bipyridine, Ipcyd = 4-iodophenylcyanamide anion, OHpcyd = 4-(3-hydroxy-3-methylbut-1-ynil)phenylcyanamide), have been prepared and characterized by UV-Vis, IR and H-1 NMR spectroscopies as well as electrochemical technique (CV). The complex cis-[Ru(bPY)(2)(lpcyd)(2)] (1) crystallized with empirical formula Of C34H24I2N8Ru in a monoclinic crystal system and space group of 3 P2(1)/c with a = 11.769(7) angstrom, b = 24.188(12) angstrom, c = 11.623(2) angstrom, beta = 91.63(3)degrees, V= 3308(3) angstrom(3) and Z = 4. (c) 2004 Elsevier B.V. All rights reserved.

Technomimetic molecules are destinated to mimic the function of common technical devices. In the case of the molecular switch, we have demonstrated the possibility to control an intramolecular electron transfer by photoisomerisation. Our present research is focussed on the electrical control of 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. For the rotary molecular motor project, we have prepared a molecule based on the piano-stool structure, with a << stator >> destinated to be grafted on an oxide surface and a << rotor >> bearing redox 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 finally evoked.

We present here our strategy to build a molecular motor following the bottom-up approach. This motor is designed to operate as a single molecule which is supposed to convert an electric current into a directionally-controlled rotary motion.

The title compound, molecular formula C30H40N10, crystallizes and exhibits a cisoidal conformation around a central p-phenylenediamine ring suggesting that this bis-tripodal ligand is highly flexible and could be accommodated by many and original metal coordinations. All four five-membered pyrazole rings are identical. The molecule presents an inversion centre that coincides with the phenyl ring centre: pyrazole rings are two-by-two equivalent. The electrostatic spatial intramolecular repulsion between N4 and N5 is probably responsible for this general arrangement. These data emphasize the basic character of nitrogens N4 and N5.

A short route to prepare a ruthenium complex with a pentaphenyl substituted cyclopentadienyl and a hydrotris(indazolyl)borate ligand is described: this complex can be seen as an organometallic molecular turnstile.

The tripodal ligand N,N-bis-(3-carbomethoxy-5-methylpyrazol-1-yl)methyl aniline (2) has been prepared by the condensation of aniline with two equivalents of N-hydroxymethyl[3-carbomethoxy-5-methyl]pyrazole. The molecule consists of two structurally analogous 3-carbomethoxy-5-methylpyrazol-1-ylmethyl moieties, which adopt a transoidal conformation via a central aniline ring, suggesting that this tripodal ligand is highly flexible and could accommodate many metals by coordination.

The reaction of [Ru(bpy)(tpy)(Ipcyd)](+) (bpy = 2,2'-bipyridine, tpy = 2,2':6',2"-terpyridine, Ipcyd = 4-iodophenylcyanamide anion) with diethynylbenzene in a Sonogashira cross-coupling reaction gives an unprecedentedly long and conjugated dinuclear complex [{[Ru(bpy)(tpy)](2)(mu-dcpeb)}(BPh4)(2)].4(PhCH3) (dcpeb = dicyanamidophenylethynylbenzene dianion), The crystal structure data are as follows: crystal system monoclinic, space group P2(1)/c(1) with a = 12.6960(3), b = 34.0960(10), c = 15.3540(4) Angstrom, beta = 110.7381(15)degrees, V = 6215.8(3) Angstrom(3), and Z = 2. The structure was refined to a final R factor of 0.063. The metal ions are separated by a through-space distance of 24.9 Angstrom. ((C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).

Following the considerations initiated in 1988 on molecular bistability (O. Kahn and J.-P. Launay, Chemtronics, 1988, 3, p. 140), we discuss the necessary conditions to obtain a unidirectional molecular rotation (able to perform work if the motion is maintained by energy supply), starting from a molecular system presenting multistability. This appears possible by driving its potential energy curve between two states, the most efficient way using two asymmetric potentials shifted one from the other. The classical model of this motor is built from a cogged wheel, with two active pawls in an out-of-phase synchronization.

Intramolecular electron-transfer phenomena in the radical anions derived from the partial reduction of diradicals (E,E)-p-divinylbenzene-beta,beta'-ylene bis(4-tetradecachlorotriphenylmethyl) diradical (1) and (E,E)-m-divinylbenzene-beta,beta'-ylene bis(4-tetradecachlorotriphenylmethyl) diradical (2) have been studied by optical and ESR spectroscopy. The synthetic methodology used allows for complete control of the geometry of diradicals 1 and 2, which have para and meta topologies, respectively, as well as of their E/Z isomerism. This fact is used to show the influence of the different topologies on the ease of electron transfer, which is larger for the para than for the meta isomer, in which a small or negligible electronic coupling is observed. A related monoradical compound (E)-bis(pentachlorophenyl)[4-(4-bromophenyl-beta-styryl)-2,3,5,6-tetrachlorophenyl]-methyl radical (3), which has only one such redox site, has also been obtained and studied for comparison purposes.

The complex [Ru(bpy)(tpy)(Ipcyd)]+ (where bpy: 2,2′-bipyridine, tpy: 2,2′:6′,2′′-terpyridine and Ipcyd: 4-iodophenylcyanamide anion) has been synthesized. An extensive characterization was carried out using IR, 1H and 13C NMR, ES-MS, UV–Vis, electrochemistry, EPR and X-ray single crystal diffraction analysis. Cyclic voltammogram shows an irreversible anodic peak around 0.7 V/ECS, the shape of the wave is typical of an electrochemical-chemical (EC) mechanism with an half-life time in the order of seconds for the generated species. Oxidation of the title compound has been investigated in order to explore its ability as a magnetic probe for further electronic studies on dinuclear complexes. The EPR spectrum at 100 K of the monooxidized species displays g⊥=2.00 and g∣∣=1.96 attributed to the presence of a radical coming from the phenylcyanamide oxidation, in relative good agreement with EH and ZINDO calculations.