Ligands terpyridine

Vectorial transfer of electronic energy in rod-like ruthenium-osmium complexes with bis-2,2, 2"-terpyridine ligands 97CC333. 

For instance, some time ago Newkome et al. reported the synthesis of ruthenium based dendrimers [170]. A dendrimer (80) with twelve peripheral terpyridine ligands was built around a central quaternary carbon-based core. In the final step complexation between the terminal ligand of the dendrimer and a terpyridinyl ruthenium chloride building block afforded the dodecaruthenium cascade molecule 80 (Fig. 35). Thus, preconstructed cores and dendritic fragments were linked by Ru2+ as the connecting unit and this mode of connectivity could be denoted by [—(Ru)—]. 

Bipyridines were efficiently used in supramolecular chemistry [104], Since the molecule is symmetric no directed coupling procedure is possible. In addition, 2,2 6/,2//-terpyridine ligands can lead to several metal complexes, usually bis-complexes having octahedral coordination geometries [105,106], Lifetimes of the metal-polymeric ligand depend to a great extent on the metal ion used. Highly labile complexes as well as inert metal complexes have been reported. The latter case is very important since the complexes can be treated as conventional polymers, while the supramolecular interaction remains present as a dormant switch. 

A general strategy developed for the synthesis of supramolecular block copolymers involves the preparation of macromolecular chains end-capped with a 2,2 6/,2//-terpyridine ligand which can be selectively complexed with RUCI3. Under these conditions only the mono-complex between the ter-pyridine group and Ru(III) is formed. Subsequent reaction with another 2,2 6/,2"-terpyridine terminated polymer under reductive conditions for the transformation of Ru(III) to Ru(II) leads to the formation of supramolecular block copolymers. Using this methodology the copolymer with PEO and PS blocks was prepared (Scheme 42) [ 107]. 

SCHEME 33. Self-assembled glycoclusters using a monosubstituted terpyridine ligand.273... 

SCHEME 34. Alternative strategy used by Constable et al. for the construction of a dimeric iron(II) complex built around a terpyridine ligand.274... 

Terpyridine ligands are known to form mono- and Ins-complexes with a wide variety of transition metal ions [321]. The stability constants and the kinetics of formation of these different complexes strongly depend on the nature of the used metal ions [322], In this respect, Rum is known to form a very stable mono-complex with one terpyridine ligand, while Ru11 only forms a stable bzs-complex with two terpyridine ligands [323]. 

Terpyridine moieties have been introduced as a terminal unit of macromolecules. In a subsequent procedure the two-step self-assembly process based on Rum/Run chemistry was used for polymers end-capped with the 2,2/ 6/,2 -terpyridine ligand. More precisely, the terpyridine-functionalized polymers were complexed with RUCI3 to selectively form a mono-complex. In a further step, this mono-complex was reacted under reducing conditions with other uncomplexed 2,2/ 6/,2/-terpyridine-terminated polymer blocks in order to form an asymmetrical AB ruthenium(II) frzs-complex. 

Table 6 compiles the electrode potentials of the chromium complexes with phenantroline, bipyridine and terpyridine ligands, respectively25-27. 

It has been mentioned previously that the formation of 2 1 Co 02 -peroxodimers is generally believed responsible for the irreversible coordination of dioxygen. In apparent contrast with this affirmation, the mixed bipyridine/terpyridine ligands complex [ Co(terpy)(bipy) 2 (fi-02)]4 +, the molecular structure of which is shown in Figure 16, constitutes an example of reversible coordination of the peroxo group.22... 

Complexes containing 2,2 6, 2"-terpyridine ligands and cyclometallated analogs... 

Terpyridine ligands carrying aryl substituents have been widely studied and this includes the use of aryl spacers between two tpy ligands to construct potentially bridging ligands. 

Terpyridine ligand 20, with appropriate functionalization at the 4 position (introduced by nucleophilic displacement of a 4 -chloro substituent) is the key building block used by Newkome and by Constable. The assembly of the beautiful dodecaruthenium macromolecule 24 carrying a 24 charge was an early highlight... 

The photoelectrochemical performances given by the mononuclear complex [Ru(dcbH2)2(NCS)2] have been surpassed by an analogous species based on the terpyridine ligand.8... 

Scheme 54 Coupling of a Terpyridine Ligand to a Cysteine Side Chain1104 ...

The spacer between terpyridine units affects PL of the zinc(II) polymers. The emission colors are blue (Tpl,film =0.20), green (0.50), green (0.20), green (0.55), and yellow (0.40) with Xmax at 450, 546, 530, 535, and 567 nm, respectively. The difference in the emission colors could be attributed to the difference in conjugation length of the terpyridine ligands. 

We selected two types of molecular wires to form desired structures for the electrode. The first has a linear structure with a bis-terpyridine moiety (Lp azobenzene-bridged bis-terpyridine ligand, L2 phenylene-bridged bis-terpyridine ligand), as illustrated in Figure 2. This type of wire can form a linear structure such as a bead curtain. The second has a triangular structure with three terpyridine... 

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