Photochemical reactivity , ruthenium

It is, thus, important that the ruthenium(II) complexes that are to be used as building blocks of the future machines contain sterically hindering chelates so as to force the coordination sphere of the metal to be distorted from the perfect octahedral geometry. We will discuss the photochemical reactivity of rotaxanes and catenanes of this family as well as non-interlocking systems like scorpionates since the lability of bulky monodentate ligands could also lead to useful photosubstitution reactions. 

A particularly promising feature of the Ru(terpy)(phen)(L)2+ series, in relation to future molecular machine and motors, is related to the pronounced effect of steric factors on the photochemical reactivity of the complexes [84]. When the bulkiness of the spectator phenanthroline moiety was increased, the steric congestion of the coordination sphere of the ruthenium complex also increased. This increased congestion was qualitatively correlated to the enhanced photoreactivities of these complexes (Fig. 14). More specifically, changing phen for dmp increased by one to two orders of magnitude the quantum yield of the photosubstitution reaction of L by pyridine with L = dimethylsulfide or 2,6-dimethoxybenzonitrile. 

Tfouni E, Krieger M, McGarvey BR, Franco DW. Structure, chemical and photochemical reactivity and biological activity of some ruthenium amine nitrosyl complexes. Coord Chem Rev 2003 236 57-69. 

Reactive Intermediates in the Thermal and Photochemical Reactions of IHnuclear Ruthenium Carbonyl Clusters... 

When we took ruthenium dodecacarbonyl and studied its photochemical reactions with triphenyl phosphine, we observed an increase in the quantum yield with increasing triphenyl phosphine concentration. The plot is curved and appears to be approaching a limiting value of < >. This implies that there is a reactive intermediate which can undergo competitive reaction, either in the forward direction (where the rate term is k [L]) or in the reverse direction (where the intermediate reverts back... 

The possibility of the practical application of the catalytic photode-composition of water based on the reactivity of the excited states of tris(2,2 -bipyridine) complexes of ruthenium(III) and ruthenium(II) has attracted considerable interest, but it is now clear that the efficiency of this process is limited not only by the lack of efficient catalysts, particularly for the dioxygen-evolving path, but also by both thermal and photochemical ligand oxidation 1,2) and ligand substitution reactions (3) of the 2,2 -bipyridine complexes. The stoichiometrically analogous tris(2,2 -bipyridine) and tris(l,10-phenanthroline) complexes of both... 

Luminescent and redox-reactive building blocks for the design of photochemical molecular devices mono-, di-,tri-, and tetranuclear ruthenium(n) polypyridine complexes. [G. Denti, S. Campagna, L. Sabatino, S. Serroni, M. Ciano, V. Balzani, Inorg. Chem. 1990, 29(23), 4750-4758] [ 830]. 

In the previous chapter (07AHC(93)185), complexes of polypyridine ligands with non-transition and early transition metals were considered. Most publications, however, are dedicated to the rhenium(I) and ruthenium(II) complexes, and the number of sources is so high that they deserve separate chapters. Moreover, studies of such complexes become more and more popular due to their unique photochemical and electrochemical properties and ability to form molecular assemblies and nanocrystallites. Herein we consider organomanganese and organorhenium complexes of polypyridine ligands. As always in this series of chapters, emphasis will be on the synthetic and coordination aspects, as well as reactivity. We have attempted to document all the publications on applied aspects, but without analyzing them since this could be the subject of a separate chapter. 

Hopf FR, O Brien TP, Scheidt WR, Whitten DG (1975) Structure and Reactivity of Ruthenium (II) Porphyrin Complexes Photochemical Ligand Ejection and Formation of Ruthenium Porphyrin Dimers. J Am Chem Soc 97 277-281... 

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