An improved synthesis, crystal structures, and metallochromism of salts of [Ru(tolyl-terpy)(CN)(3)](-)

The previously reported complex [Ru(ttpy)(CN)(3)] [ttpy = 4'(p-tolyl)-2,2':6',2"-terpyridine] is conveniently synthesised by reaction of ttpy with Ru(dmso)(4)Cl-2 to give [Ru(ttpy)(dmso)Cl-2], which reacts in turn with KCN in aqueous ethanol to afford [Ru(ttpy)(CN)(3)] which was isolated and crystallographically characterised as both its (PPN)(+) and K+ salts. The K+ salt contains clusters containing three complex anions and three K+ cations connected by end-on and side-on cyanide ligation to the K+ ions. The solution speciation behaviour of [Ru(ttpy)(CN)(3)] was investigated with both Zn2+ and K+ salts in MeCN, a solvent sufficiently non-competitive to allow the added metal cations to associate with the complex anion via the externally-directed cyanide lone pairs. UV-Vis spectroscopic titration of (PPN)[Ru(ttpy)(CN)(3)] with Zn(ClO4)(2) showed a blue shift of 2900 cm (1) in the (MLCT)-M-1 absorption manifold due to the ` metallochromism' effect; a series of distinct binding events could be discerned corresponding to formation of 4:1, 1:1 and then 1:3 anion: cation adducts, all with high formation constants, as the titration proceeded. In contrast titration of (PPN)[Ru(ttpy)(CN)(3)] with the more weakly Lewis-acidic KPF6 resulted in a much smaller blue-shift of the 1MLCT absorptions, and the titration data corresponded to formation of 1:1 and then 2: 1 cation: anion adducts with weaker stepwise association constants of the order of 10(4) and then 10(3) M (1). Although association of [Ru(ttpy)(CN)(3)] resulted in a blue-shift of the (MLCT)-M-1 absorptions, the luminescence was steadily quenched, as raising the (MLCT)-M-3 level makes radiationless decay via a lowlying (MC)-M-3 state possible. (C) 2010 Elsevier B. V. All rights reserved.