Bipyridyl chromophore

The bipyridyl chromophore has been extensively used in lanthanide coordination chemistry. In addition to those based on the Lehn cryptand (see Section IV.B.4), a number of acyclic ligands have also employed this group. One such ligand is L17, which binds to lanthanide ions such that one face of the ligand is left open (Scheme 3) (60). As expected, luminescence is extremely weak in water and methanol, but stronger in acetonitrile ( = 0.30, 0.14 for europium and terbium, respectively). In addition, the nature of the counter ion can... 

High quantum yields and long lifetimes have been reported for a series of calixcrowns with appended bipyridyl chromophores, such as L48 (82). Photophysical studies in acetonitrile gave lifetimes of 0.95-1.38 and 1.83-1.93 ms, and quantum yields of 0.18 0.32 and 0.32-0.39 for europium and terbium complexes, respectively. 

Complexes of calixarenes with bipyridyl chromophores can be stabilized by the addition of anionic side arms, such as iminodiacetate units (85). Whilst the lanthanide complexes of ligands [L51]4- and [L52]4- are not soluble in water, their photophysical properties in... 

In an impressive demonstration of self-assembly, Lehn and co-workers showed that 32 (Figure 6.16) reacts with an equimolar amount of ferric chloride in ethylene glycol at 170 °C to yield the red solution expected for the presence of an iron(Il) tris-bipyridyl chromophore. Molecular models indicated that the three bipyridyl fragments of each ligand are best accommodated by co-ordination to three differ-... 

The bipyridyl chromophore has been extensively used in lanthanide coordination chemistry. In addition to those based on the Lehn cryptand (see Section IV.B.4), a number of acyclic ligands have also employed this group. One such ligand is which binds to... 

The bipyridyl-iV,iV-dioxide chromophore has been appended to a calix[4]arene to give L50, and complexed with europium and terbium... 

Alteration of the chromophore by conversion of some of the bipyridyl groups to their N-oxide derivative leads to a significant improvement in the luminescence performance (88). Although the lifetimes of the europium complexes of ligands L54 and L55 were still less than a millisecond, the quantum yields of 0.15 and 0.20 respectively are significantly better. 

Recently, two cryptands and their lanthanide complexes have been synthesized which include either a bipyridyl (L56) or pyridyl (L57) chromophore (89). These have proved effective at populating the lanthanide excited states. Aqueous luminescence lifetimes of up to... 

Hyslop and coworkers reported an Os(II) bipyridyl carbonyl complex (Fig. 7) covalently linked to both free base and Zn(II) tetraphenylpor-phyrin [45]. The Os(II) chromophore, having a CO ligand, has a luminescence maximum of 589 nm in CH2CI2 and excitation of the complex results in energy transfer to the free base porphyrin. In the mixed Os(II)/Zn(II) complex,... 

The Ru(phen)2(dppz)2+-chromophore is the electron donor in this study. It has absorbance maxima in aqueous solution at 372 and 439 nm, respectively, e = 2.48 and 2.23 x 104 M 1 cm-1. The absorbance at 439 nm arises from a metal to ligand charge transfer (MLCT) transition that is common to tris(bipyridyl)-ruthenium(II) complexes, while the absorbance at 372 arises from an intraligand... 

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