Nanostructured ruthenium complexes

Figure 38. Decay of PMC transients measured with a TSO -based nanostructured sensitization solar cell (ruthenium complex as sensitizer in the presence of 0.1 M TBAP in propylene carbonate). The transients are significantly affected by additions of iodide.40 (a) no I", (b) 2 mM r, (c) 20 mM r. (d) 200 mMT.

Among other advances, the nanostructuration of electrochemically synthesized conducting polymers has raised a lot of interest. To achieve this, one of the most straightforward and common way is the use of a scanning electrochemical microscope (SECM). Since the pioneering work of Bard, several authors have refined the conditions, improving the resolution. Heinze et al. used a PMMA matrix to confine more cleanly the electrodeposition of PPy [24], and in a further work, they could deposit micropatterns of poly(dimethoxybithiophene) with the help of electrocatalysis by a ruthenium complex, obtaining well-defined plots [25,26]. 

The ability of long alkyl chain amines to induce a shape control of ruthenium nanostructures from ruthenium complexes has been explored by other groups and significant advances have recently been described. Different protocols in organic medium leading to monodisperse nanoparticles such as stars, urchins, and hourglass, from Ru(acac)2 [71] and Ru3(CO)i2 [72], have been reported. These syntheses require the presence of an amine or a mixture of an amine plus a carboxylic acid which play a crucial role in controlling the shape of ruthenium nanocrystals... 

Bottini, M. Magrini, A. Di Venere, A. Bellucci, S. Dawson, M. L Rosato, N. Bergamaschi, A. Mustelin, T. Synthesis and characterization of supramolecular nanostructures of carbon nanotubes and ruthenium-complex luminophores. J. Nanosci. Nanotechnol. 2006, 6,1381-1386. 

A complex nanostructured catalyst for ammonia synthesis consists of ruthenium nanoclusters dispersed on a boron nitride support (Ru/BN) with barium added as a promoter (33). It was observed that the introduction of barium promoters results in an increase of the catalytic activity by 2—3 orders of magnitude. The multi-phase catalyst was first investigated by means of conventional HRTEM, but this technique did not succeed in identifying a barium-rich phase (34). It was even difficult to determine how the catalyst could be active, because the ruthenium clusters were encapsulated by layers of the boron nitride support. By HRTEM imaging of the catalyst during exposure to ammonia synthesis conditions, it was found that the... 

Fig. 5.4 depicts some results obtained in the first stages (high nuclearity complexes formation) of the synthesis in xylene solvent which leads to the formation of nanostructured powders, RuxSey, from tris-ruthenium dodeca-carbonyl (Ru3(CO)i2) and elemental selenium dissolved in an organic solvent (xylene). After 40 minutes of reaction, l3C-NMR spectrum (Fig. 5.4 (c)) puts in evidence the formation of a new polynuclear chemical precursor with a chemical shift 8 of 198.89 ppm (i.e., Ru4Se2(CO)n)- Selenium takes part in the coordination sphere. The peak intensity with the chemical shift of 199.67 ppm, corresponds to the initial chemical precursor which decreases as a function of the synthesis reaction time (Fig. 5.4(a)). Other chemical shifts (with minor peak intensities) on both sides of the 13C-NMR spectrum, which put in evidence the complex interplay of the reaction, are also observed. 

Concerning more complex systems such as colloidal suspensions of nanoparticles, Santini and co-workers reported studies on the influence of the size of the nanostructures in ionic liquids and the size distribution of ruthenium nanoparticles synthesised therein by reduction of a nonpolar organometallic complex. The stabilisation mechanism proposed is based on a tenplate effect linked to the structure of the ionic liquids [66, 75, 76], not to electrostatic stabilisation (due to DLVO-type forces as observed in colloidal suspensions in aqueous electrolytes). Watanabe and co-workers also observed that silica nanoparticle colloids couldn t be stabilised in ionic liquids without surface-grafted polymer chains, again indicating that DLVO-type forces are insufficient for effective stabilisation, as expected from the short screening length in these media composed mainly of ions [77]. 

G. Buntkowslg, From Molecular Complexes to Complex Metallic Nanostructures - Solid-State NMR Studies of Ruthenium-Containing Hydrogenation Catalysts, ChemPhysChem, 2013, 14, 3026. 

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