Terpyridines functionalised with ferrocenyl groups of different redox potential

2,2′:6′,2′′-Terpyridines bearing a substituent × in the 4′-position [3a: × = Fc–C≡C–p-C6H4; 3b: × = Fc#–C≡C–p-C6H4; Fc = (C5H5)Fe(C5H4), Fc# = (C5Me4H)Fe(C5Me4)] were prepared by Pd0-catalysed cross-coupling reactions. 3b was characterised by X-ray structure analysis. [(3a)RuCl2(DMSO)] (4a) and [(3b)RuCl2(DMSO)] (4b) were obtained by reaction of [RuCl2(DMSO)4] with 1 equivalent of 3a and 3b, respectively, while the analogous reaction with 2 equivalents afforded [(3a)2Ru][PF6]2 (5a) and [(3b)2Ru][PF6]2 (5b), respectively, after precipitation with aqueous [NH4][PF6]. Similarly, [(3a)Ru(tpy)][PF6]2 (6) was isolated from the reaction of 4a with 2,2′:6′,2′′-terpyridine (tpy). Compounds 3 and 5 were investigated by cyclic voltammetry, which revealed that the introduction of eight methyl groups leads to the expected cathodic shift of the E0′ values of ca. 0.44 V for the ferrocenyl-centered redox processes.