title: Curly-curly, loop-loop: homoleptic metal(ii) complexes of pyridinecarbaldehyde 4'-(2,2':6',2''-terpyridyl)hydrazones and their coordination polymers.
abstract: The ligands 4-, 3- and 2-pyridinecarbaldehyde 4'-(2,2':6',2''-terpyridyl)hydrazone (, and ) have been prepared and characterized. In the homoleptic iron(ii) and ruthenium(ii) complexes, the nitrogen donor atoms of the pendant pyridine rings subtend an obtuse angle ( approximately 155 degrees ) at the metal centre, thus providing an expanded ligand, which can be used for the assembly one-dimensional coordination polymers with an undulating backbone. Protonation of the pendant pyridine rings in [FeL(2)](2+) (L = , , ) or [RuL(2)](2+) (L = , ) leads to a colour change from purple to blue, or red to pink, respectively, as the MLCT band shifts to a lower energy. The structural data for [Fe(H)()][PF(6)](3).3.5MeCN.2.5H(2)O (where [H](+) is the monoprotonated ligand) show that the [Fe(H)()](3+) cations form one-dimensional chains supported by N(py)HN(py) hydrogen bonds and that the undulating chains pack to give a porous material, with channels that accommodate the anions and solvent molecules. A single-crystal X-ray diffraction determination of {[Fe(NCS)(2)(Ru()(2))(2)][Fe(2)(NCS)(6)(OEt)(2)(EtOH)(2)][NCS](2).4EtOH.H(2)O}(n) reveals that pairs of [Ru()(2)](2+) cations connect {Fe(NCS)(2)} units to give a one-dimensional polymer comprising of linked metallamacrocycles.
authors.affiliation: Department of Chemistry, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland.
authors.forename: Jonathon E
authors.initials: JE
authors.lastname: Beves
authors.forename: Edwin C
authors.initials: EC
authors.lastname: Constable
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Housecroft
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Kepert
authors.forename: Markus
authors.initials: M
authors.lastname: Neuburger
authors.forename: David J
authors.initials: DJ
authors.lastname: Price
authors.forename: Silvia
authors.initials: S
authors.lastname: Schaffner
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Zampese