title: Nickel(II) and iron(II) triple helicates assembled from expanded quaterpyridines incorporating flexible linkages.
abstract: In the present study the interaction of Fe(II) and Ni(II) with the related expanded quaterpyridines, 1,2-, 1,3- and 1,4-bis-(5'-methyl-[2,2']bipyridinyl-5-ylmethoxy)benzene ligands (4-6 respectively), incorporating flexible, bis-aryl/methylene ether linkages in the bridges between the dipyridyl domains, was shown to predominantly result in the assembly of [M(2)L(3)](4+) complexes; although with 4 and 6 there was also evidence for the (minor) formation of the corresponding [M(4)L(6)](8+) species. Overall, this result contrasts with the behaviour of the essentially rigid 'parent' quaterpyridine 1 for which only tetrahedral [M(4)L(6)](8+) cage species were observed when reacted with various Fe(II) salts. It also contrasts with that observed for 2 and 3 incorporating essentially rigid substituted phenylene and biphenylene bridges between the dipyridyl domains where reaction with Fe(II) and Ni(II) yielded both [M(2)L(3)](4+) and [M(4)L(6)](8+) complex types, but in this case it was the latter species that was assigned as the thermodynamically favoured product type. The X-ray structures of the triple helicate complexes [H(2)O⊂Ni(2)(4)(3)](PF(6))(4)·THF·2.2H(2)O, [Ni(2)(6)(3)](PF(6))(4)·1.95MeCN·1.2THF·1.8H(2)O, and the very unusual triple helicate PF(6)(-) inclusion complex, [(PF(6))⊂Ni(2)(5)(3)](PF(6))(3)·1.75MeCN·5.25THF·0.25H(2)O are reported.
authors.affiliation: School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Qld. 4814, Australia.
authors.forename: Christopher R K
authors.initials: CR
authors.lastname: Glasson
authors.forename: George V
authors.initials: GV
authors.lastname: Meehan
authors.forename: Cherie A
authors.initials: CA
authors.lastname: Motti
authors.forename: Jack K
authors.initials: JK
authors.lastname: Clegg
authors.forename: Peter
authors.initials: P
authors.lastname: Turner
authors.forename: Paul
authors.initials: P
authors.lastname: Jensen
authors.forename: Leonard F
authors.initials: LF
authors.lastname: Lindoy