Strategies for the assembly of homo- and hetero-nuclear metallosupramolecules containing 2,2′ : 6′,2″-terpyridine metal-binding domains

Abstract
A new strategy for the convergent synthesis of metallosupramolecular oligomers has been elaborated. The key step is the formation of the ligand-complexes[Ru(X-terpy)(dpqtpy)][PF6]2(X-terpy = terpy, eoterpy, cterpy or msterpy) from the reaction of [Ru(X-terpy)Cl3] with 6′,6″-di(2-pyridyl)-2,2′ :4′,4″ :2″,2‴-quaterpyridine (dpqtpy) in ethane-1,2-diol. These complexes have one non-co-ordinated terpyridine (terpy) domain, and reacted instantaneously with iron(II) salts to give the heterotrinuclear complexes [(X-terpy)Ru(dpqtpy)Fe(dpqtpy)Ru(X-terpy)][PF6]6. Similar reactions with cobalt(II) acetate gave the paramagnetic d7 cobalt(II) complexes [(X-terpy)Ru(dpqtpy)Co(dpqtpy)Ru(X-terpy)][PF6]6 which may be oxidised to the kinetically inert diamagnetic d6 cobalt(III) complexes [(X-terpy)Ru(dpqtpy)Co(dpqtpy)Ru(X-terpy)][PF6]7. The reaction of [Ru(X-terpy)(dpqtpy)][PF6]2 with ‘RuCl3·nH2O’ yielded the homotrinuclear complex [(terpy)Ru(dpqtpy)Ru(dpqtpy)Ru(terpy)][PF6]6. The ruthenium–osmium heterodinuclear complex [(terpy)Ru(dpqtpy)Os(terpy)][PF6]4 was readily obtained from the reaction of [Ru(terpy)(dpqtpy)][PF6]2 with [Os(terpy)Cl3]. Some representative mixed-ligand homodinuclear complexes [(X-terpy)Ru(dpqtpy)Ru(Y-terpy)][PF6]4 containing both electron-releasing and electron-withdrawing terminator ligands were prepared from the reaction of [Ru(X-terpy)(dpqtpy)][PF6]2 with an equimolar quantity of [Ru(Y-terpy)Cl3]. The specific examples with mixed terminator ligands were [(terpy)Ru(dpqtpy)Ru(dmterpy)][PF6]4, [(terpy)Ru(dpqtpy)Ru(msterpy)][PF6]4 and [(dmterpy)Ru(dpqtpy)Ru(msterpy)][PF6]4. All of the compounds were fully characterised, and detailed spectroscopic, spectrometric and electrochemical studies are described.

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