Synthesis and co-ordination behaviour of 6′,6″-bis(2-pyridyl)-2,2′ : 4,4″ : 2″,2″′-quaterpyridine; ‘back-to-back’ 2,2′ : 6′,2″-terpyridine

The oligopyridine 6′,6″-bis(2-pyridyl)2,2′ : 4,4″ : 2″,2″′-quaterpyridine (L) has been prepared. It may be regarded as a ‘back-to-back’ analogue of the well known 2,2′ : 6′2″-terpyridine (terpy). Complexes with ruthenium(II) and palladium(II) have been characterised. The diruthenium(II) complex cation (terpy)RuLRu(terpy)4+ has been shown to exhibit no Ru–Ru interactions, and behaves as two non-interacting Ru(terpy)2 units.