Metal-polypyridine complexes

The aim of this chapter is limited to reviewing some recent developments concerning luminescent dendrimers that can play the role of ligands and sensors for luminescent and nonluminescent metal ions, mainly investigated in our laboratories, with particular references to transition metal or lanthanide ions. We will not discuss dendrimers constituted by polypyridine metal complexes [21] and porphyrins [22] since it is outside the scope of the present paper. 

Polypyridine metal complexes have been extensively investigated from an electro-... 

Temperature jump [25] with Joule heating was used in an early study of rapid outer-sphere electron-transfer reactions [22] between polypyridine metal complexes and haxachloro- and hexabromometalates, Eq. 25,... 

Electron-transfer Processes in Mononuclear Polypyridine Metal Complexes ... 

Spiropyran- and Spirooxazine-Containing Polypyridine Metal Complexes. 212... 

El-ghayoury A, Harriman A, Khatyr A, Ziessel R. Controlling Electronic Communication in Ethynylated-Polypyridine Metal Complexes. Angew. Chem. Int. Ed. 2000 39 185-189... 

Dendrimers Containing Polypyridine-Type Metal Complexes. 203... 

Dendrimers built around a metal complex as a core. These compounds can be considered metal complexes of ligands carrying dendritic substituents (Fig. 1 a). The most commonly used metal complex cores are porphyrin complexes, polypyridine complexes, and ferrocene-type compounds. 

The electroactive units in the dendrimers that we are going to discuss are the metal-based moieties. An important requirement for any kind of application is the chemical redox reversibility of such moieties. The most common metal complexes able to exhibit a chemically reversible redox behavior are ferrocene and its derivatives and the iron, ruthenium and osmium complexes of polypyridine ligands. Therefore it is not surprising that most of the investigated dendrimers contain such metal-based moieties. In the electrochemical window accessible in the usual solvents (around +2/-2V) ferrocene-type complexes undergo only one redox process, whereas iron, ruthenium and osmium polypyridine complexes undergo a metal-based oxidation process and at least three ligand-based reduction processes. 

Keywords Sonogashira polycondensation Hybrid polymers Polypyridine ligands Copolymers Macromolecular metal complexes... 

Room temperature emission has been observed for a number of transition metal complexes. Examples include Rh111 ammines,53 [Pt(CN)4]2-,54 and some Cu1 phosphine complexes.55 An important class is that of the polypyridine complexes of Ru11 and related species.56 This last emission, probably from a 3CT state, is quite strong and its occurrence has made possible a number of detailed studies of electron transfer quenching reactions. 

Some metal complexes with polypyridine ligands similar to Dye 2 have also been investigated as sensitizing dyes. Ferrere and Gregg73) synthesized cis-Fen(dcbpy)2(CN)2 complex (Dye 8), and Bignozzi el al.74i75) compared properties of m-Osn(dcbpy)2(CN)2 (Dye 9) with comparable m-Rull(dcbpy)2(CN)2 (Dye 10). The efficiencies are much lower than that of Dye 2, but they proposed the... 

Balzani et al. prepared dendrimers with metal complexes serving both as core [36] and as branching unit The metallodendrimer in Fig. 2.10 is constructed solely from polypyridine ligands and transition metal ions. Such dendritic transition metal complexes can be synthesised both convergently and divergently and different transition metal ions (ruthenium/osmium) can be incorporated. This provides a means of influencing the luminescence properties of the den-drimer. Thus the energy transfer process proceeds from the inside outwards in... 

A dendrimer with metal complexes both in the core and in the branches was described by Balzani et al. The luminescent, heteroleptic (having different ligands), dendritic polypyridine-ruthenium or polypyridine-osmium complex can be prepared both divergently and convergently [130] (cf. Section 2.5.2). 

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