Nickel(ii) and iron(ii) triple helicates assembled from expanded quaterpyridines incorporating flexible linkagesElectronic supplementary information (ESI) available: ESI-HRMS of [Fe2(4)3](PF6)4and an additional X-ray structure figure for the [Ni2(6)3]4+cation. CCDC reference numbers [CCDC 824369–824371]. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1dt10820d

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 (4–6respectively), incorporating flexible, bis-aryl/methylene ether linkages in the bridges between the dipyridyl domains, was shown to predominantly result in the assembly of [M2L3]4+complexes; although with 4and 6there was also evidence for the (minor) formation of the corresponding [M4L6]8+species. Overall, this result contrasts with the behaviour of the essentially rigid ‘parent’ quaterpyridine 1for which only tetrahedral [M4L6]8+cage species were observed when reacted with various Fe(ii) salts. It also contrasts with that observed for 2and 3incorporating essentially rigid substituted phenylene and biphenylene bridges between the dipyridyl domains where reaction with Fe(ii) and Ni(ii) yielded both [M2L3]4+and [M4L6]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 [H2O⊂Ni2(4)3](PF6)4·THF·2.2H2O, [Ni2(6)3](PF6)4·1.95MeCN·1.2THF·1.8H2O, and the very unusual triple helicate PF6−inclusion complex, [(PF6)⊂Ni2(5)3](PF6)3·1.75MeCN·5.25THF·0.25H2O are reported. [ABSTRACT FROM AUTHOR]