Kinetic and mechanistic studies of mono(terpyridine)- to bis(terpyridine)-nickel(II) complex formation reactions involving a range of substituted 2,2′:6′,2″-terpyridine ligands: an investigation of π-stacking interactions in outer-sphere complexes.

Using a range of substituted 2,2':6',2"-terpyridine ligands, the effects of π-stacking on the rates of formation of bis(terpyridine)nickel(II) complexes have been investigated in 70:30 v/v % methanol:water. Compared with the rates of formation of the mono(terpyridine)nickel(II) complexes, for the bis(terpyridine)nickel(II) complexes at 25°C, rate enhancements in the range 11-146 were found. For unsubstituted 2,2':6',2"-terpyridine studied in the same solvent mixture, the rate enhancement at 25°C is 11, whereas for 4'-(2-naphthyl)-2,2':6',2"-terpyridine the rate enhancement is 146.