Multi-pyridine decorated Fe(ii) and Ru(ii) complexes by Pd(0)-catalysed cross couplings: new building blocks for metallosupramolecular assemblies

Abstract

Eight metal complexes of the type [M(tpy)₂]²⁺ (tpy = 2,2′:6′,2′′-terpyridine) featuring four pendant pyridine rings are reported and characterised by NMR, MS, absorption spectroscopy and electrochemical methods. Palladium-mediated Suzuki and Sonogashira cross-coupling reactions were performed on both free 4′-(3,5-dibromophenyl)-tpy and its Ru(II) complex in good yields. The ready N-alkylation of the pendant pyridyl units has significant influence on the absorption and electrochemical reduction of the complexes, processes which are localised on the periphery and leaves the [Ru(tpy)₂]²⁺ core essentially unaffected. The binding of metal ions by the free pyridines is also demonstrated as means of assembling larger ordered non-covalent structures.