2,2 ,6",2"-Terpyridine, reaction with complexes

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]. 

Holyer RH, Hubbard CD, Kettle SFA, Wilkins RG. Tbe kinetics of replacement reactions of complexes of tbe transition metals with 2,2, 2"-terpyridine. Inorg Chem 1966 5 622-625. 

An interesting example that illustrates the role of activation parameters in providing an understanding of the reaction mechanism was reported recently.47 A mthenium(III) terpyridine-4 -carboxylate complex, RuraCOO, reacts with tri-A / r-butylphenol in acetonitrile according to Scheme 8.10. 

In another recent example, a terpyridine fragment has been appended to the lower rim of a fi-CD, and a subsequent reaction with Ru(ttp)Cl3 yielded the complex 47, [(/ -CD-ttp)Ru(ttp)][PF6]2. 

While the use of one terpyridine monomer results in only one dimeric complex, the use of more than one monomer leads to a mixture of complexes. Two monomers (X and Y) will lead to 25% dimeric X X, 25% dimeric Y Y, and 50% mixed complex X Y determined by high-pressure liquid chromatography (HPLC) of reaction products. Complexes (X Y) and (Y X) are degenerate and only one need be considered. Each bis(terpyridine) metal complex exists as a pair of stereoisomers due to the two possible arrangements around the metal center, and no attempt was made to distinguish or separate these stereogenic pairs. The total number of components of these combinatorial libraries must include both symmetric and asymmetric complexes. If n terpyridine monomers are combined, the same number of symmetric complexes (X X) are formed. The number of asymmetric complexes (X Y) formed is /[( -2) 2 ] or better represented as n(n-l)/2. Thus the total number of dimeric complexes is the sum of n and ( -l)/2, which is n(n+l)/2. For example, a library with 5 monomers will form 15 dimers, 10 monomers will produce 55 dimers, and 20 monomers will produce 210 dimers. 

Newcome and coworkers have reported the synthesis of a tetraarm complex containing two ruthenium coordination complexes in each branch. Polymer 91 was prepared by reaction of a core molecule containing four terpyridine units with 4 eq of a bimetallic complex containing a reactive ruthenium trichloride moiety. 

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