Terpyridine terminal ligands

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)—]. 

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]. 

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. 

In contrast to 6-substituted-bipyridine systems such as 49, attachment of a five-membered heterocycle to the 2-position of 1,10-phenanthroline, which is a structural modification similar to the replacement of one of the terminal rings of terpyridine, does generally bring the ligand field into the crossover region and spin transitions have been observed for such systems when the heterocycle is thiazole 51 [74], imidazoline [75], triazole [76], pyrazole [77] and oxadiazole [78]. 

The spin state of iron(II) in substituted 2,2 6, 2"-terpyridine, (72), complexes depends on the position of bulky substituents—phenyl substituents in both the 6 and 6" positions give a high-spin complex phenyl substituents in the 4 and 6 positions give a complex which exists both in high-spin and in low-spin forms. Crystal structure determinations gave Fe—N bond distances in both forms of the 4,6-diphenyl complex and of the 6,6"-diphenyl complex. Each ligand in the latter com )lex has one terminal pyridine very weakly bonded to the iron, with... 

Although several examples of complexes containing the [Mn202]"" core type have been studied, only one has been found to catalyze O2 evolution in water. The complex [(terpy)(H20)Mn (/u,-0)2Mn (0H2)(terpy)] + contains the tridentate terpyridine ligand that coordinates to three meridional sites on Mn and thus positions the two terminal aquo ligands trans to the /tr-oxo bridges. The oxidation of this complex by or OCl in water was shown to produce... 

Terpyridine (tpy) forms [M(tpy)2] complexes, which are not good candidates for metal-mediated base pairs within a nucleic acid duplex because of their octahedral geometry, in which the two tpy ligands are situated in reciprocally perpendicular planes. ThCTefore, they have been used instead to connect the ends of terminally modified oligonucleotides. The tpy-modified ssDNA, which did not... 

The dicationic complex [Ru(py-NHC)(terpy)(OH2)] (terpy=2,2 6, 2 -terpyridine) containing the bidentate pyridyl-NHC ligand 3-meth)d-l-(pyridine-2-yl)imidazol-2-ylidene catalyzed the epoxidation of terminal alkenes vrith Phi (OAc)2 in CH2CI2 at room temperature (Table 12.7). In an effort to make the system reusable, a solvent system comprising a 1.2 0.8 mixture of CH2Q2 and the ionic liquid [bmim] [PFg] was employed. Tests with cyclooctene showed that this allowed 10 consecutive epoxidation reactions to be carried out without any drop in catalyst performance [107]. 

These w(2,2 6, 2"-terpyridines) may be used for the asembly of linear coordination polymers or discrete linear oligomers (Figure 9). Insoluble deep blue coordination polymers are obtained cleanly upon simply mixing solutions of either of the W5(2,2 6, 2 -terpyridines) with solutions of [Fe(H20)6][BF4]2. In contrast, stepwise reaction with suitable [Ru(Xtpy)Cl3] building blocks allows the controlled assembly of discrete oligomeric units with terminator Xtpy ligands which will confer specific electronic properties to the compounds. 

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