STRATEGIES FOR THE ASSEMBLY OF HOMO-NUCLEAR AND HETERO-NUCLEAR METALLOSUPRAMOLECULES CONTAINING 2,2'/6',2''-TERPYRIDINE METAL-BINDING DOMAINS

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)Cl-3] 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 d(7) cobalt(II) complexes [(X-terpy)Ru(dpqtpy) Co(dpqtpy)Ru(X-terpy)][PF6](6) which may be oxidised to the kinetically inert diamagnetic d(6) 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 . nH(2)O' 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)Cl-3]. 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)Cl-3]. 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.