title: When is a metallopolymer not a metallopolymer? When it is a metallomacrocycle.
abstract: We report reactions of cobalt(II) acetate with a series of ditopic bis(tpy) ligands (tpy = 2,2':6',2''-terpyridine) containing flexible polyethyleneoxy spacers (tpy-4'-O{(CH(2))(2)O}(n)-4'-tpy, n = 2, 3, 4 or 6 ligands 1-4, respectively) which result in the formation of complicated mixtures of species, presumed to be both open chain and cyclic species. Well resolved paramagnetically shifted (1)H NMR spectra are a powerful tool for the analysis of these solution systems. Upon equilibration, [n + n] metallomacrocycles are isolated as the dominant (thermodynamic) species in some cases, and the single crystal X-ray structures of [Co(2)(3)(2)][PF(6)](4)·6MeCN and [Co(2)(4)(2)][PF(6)](5)·2MeCN (a mixed cobalt(ii)/cobalt(iii) species) are presented. Oxidation of the equilibrated cobalt(II) mixtures to kinetically inert cobalt(III) species provides additional evidence for the formation of metallomacrocycles as the thermodynamic products. Single crystal structural data for [Co(3)(2)(3)][PF(6)](9)·2MeCN·3.5H(2)O, [Co(2)(3)(2)][PF(6)](6)·10MeCN and [Co(2)(4)(2)][PF(6)](6)·6MeCN confirm the assembly of [2 + 2] and [3 + 3] metallomacrocycles. PGSE NMR spectroscopy has been used to determine the hydrodynamic radii of the solution species.
authors.affiliation: Department of Chemistry, University of Basel, Switzerland. edwin.constable@unibas.ch
authors.forename: Edwin C
authors.initials: EC
authors.lastname: Constable
authors.forename: Kate
authors.initials: K
authors.lastname: Harris
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Housecroft
authors.forename: Markus
authors.initials: M
authors.lastname: Neuburger
mesh_terms: D000085:Acetates / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008024:Ligands; D047028:Macrocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*
chemical_list: D000085:Acetates; D008024:Ligands; D047028:Macrocyclic Compounds; D009942:Organometallic Compounds; D011108:Polymers; C521309:cobalt(II) acetate