Polypyridines terpyridine

Let us now consider the N6-coordinated octahedral vanadium complexes with the polypyridine ligands 1,10-phenantroline (phen), 2,2/-bipyridine (bipy) and 2,2/ 6,2//-terpyridine (terpy), Scheme 3. 

In these cases, there is the expected tetragonal distortion due to the Jahn-Teller effect in addition to the often mentioned octahedral distortion associated with polypyridine complexes. For the terpyridine complex there is the usual difference between the distances separating the metal and nitrogen atom of the central pyridine and that of the metal and the nitrogen atom of the peripheral pyridines. 

The polypyridine derivatives 48 and 49 also yield double-helical complexes of type [Cu2L2l (L = 48 or 49) and [Ag2L2] (L = 48 or 49) as well as the singlehelical species, [Ru2L(terpy)2] (where L = 49 and terpy is 2,2 6, 2"-terpyridine). The electrochemistry of the double-helical cations indicates substantial electronic coupling between the metals in each case. 

The sequence can be repeated to afford polypyridines, as in the case of the preparation of terpyridine (133) and tetrakispyridine (134) from 2,6-bis(ethylthio)pyridine.88... 

Phenyl-2,2 6, 2"-terpyridine reacts with [ Cp M(ju-Cl)Cl)2] (M = Rh, Ir) in methanol with sodium tetrafluoroborate to yield mononuclear cationic 9 (M = Rh, Ir) with the bidentate coordination mode and fluxional behavior of the ligand (98POL299). 1,4-Bis(2,2 6, 2"-terpyridyn-4 -yl)benzene with the same rhodium(III) and iridium(III) precursors forms dinuclear 10 (M = Rh, Ir) where the polypyridine ligand is still bidentately coordinated and fluxional. 

In other work with polypyridine ligands Huchital and Martell et all2 prepared [Co(terpy)(bipy)]2+ and [Oo(terpy)(phen)]2+ (terpy = 2,2 6, 2"-terpyridine phen = 1,10-phenanthroline) complexes in aqueous solutions which were identified in situ by... 

A related class of compounds has been derived by using porphyrins connected to polypyridines such as 2,2 -bipyridine, 1,10-phenantholine and 2,2 6, 2"-terpyridine. These chelating ligands form thermodynamically more stable and inert transition metal complexes than the pyridine ligand, and such porphyrins have been extensively explored for the assembly of photochemically active supramolecular systems, especially by Sauvage et The oblique... 

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