2,2 :6 .2”-Terpyridine terdentate complexation

Terpyridine commonly behaves as a chelating terdentate ligand, with the majority of complexes exhibiting 1 1 or 1 2 metalrligand ratios. The 1 2 complexes are invariably based upon an octahedral geometry, and frequently exhibit local symmetry. These complexes are discussed at the appropriate points in the text. 

The terdentate ligand 2,2 6, 2"-terpyridine, terpy (34), forms mono and bis complexes with iron(II). On the basis of a comparison of X-ray powder data it was suggested that [Fe(terpy)X2] (X = Br, I) has a five-coordinate structure similar to that of [Zn(terpy)Cl2]. In spite of early rcports claiming that the chloro complex is isomorphous with the zinc analogue, its X-ray powder pattern is different and it has been reformulated as [Fe(terpy)2][FeCl4], which is in accord with an observed magnetic moment of 4.60 BM, well below the spin-only value. 

The terpyridine-substituted difluoroborondipyrromethene dye 88 is a singlet emitter at 540 nm (18 500 cm ) and its triplet state emission extends from 550-750 nm (18200-13 300 cm ), which makes it a potential sensitizer of lanthanide NIR luminescence. In [Yb(N03)3(88)] (see fig. 75), the lanthanide ion is bound to the terdentate terpyridine and to three bidentate nitrate counterions, in a distorted tricapped antiprismatic geometry. The Ln complexes (Ln = La, Nd, Er, Yb) have large absorption coefficients (65 000 cm ... 

The terdentate ligand terpyridyl affords a range of complexes fusion of RuCla with terpy gives Ru(terpy) , while refluxing RuClj with an ethanolic solution of the ligand yields RuCl3(terpy). Both of these are doubtless 6-coordinate. Ruthenium bis(terpyridine) complexes are also attracting attention as photosensitizers [76]. 

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