Multinucleating 2,2′:6′,2″-terpyridine ligands as supramolecular building blocks; heterotrinuclear complexes and the crystal and molecular structure of 6′,6″-bis(2-pyridyl)-2,2′:4′,4″:2″,2‴-quaterpyridine (btpy)

Abstract
The crystal structure of the dinucleating 2,2′:6′,2″-terpyridine ligand 6′,6″-bis(2-pyridyl)-2,2′:4′,4″:2″,2‴-quaterpyridine (btpy) has been determined and the two metal-binding tpy domains shown to be essentially planar and co-planar (P 1, a = 6.304(2), b = 8.208(2), c = 11.535(3) Å, α = 97.42(2), β = 104.25(2), γ = 96.23(2)°, Z = 1, d c = 1.36 g cm−3, 2214 unique observed reflections with I > 1.5[sgrave] (I), R = 0.0583); a methodology involving sequential reaction with non-labile and labile metal centres allows the specific assembly of heterometallic supramolecular oligomers such as [(Xtpy)Ru(btpy)M(btpy)Ru(Ytpy)]n+ (M = cobalt(II), cobalt(III) or iron).