New alkynyl- and vinyl-linked benzo- and aza-crown etherbipyridyl ruthenium(II) complexes which spectrochemically recognize Group IA and IIA metal cations

Abstract

A new alkynyl-linked bis(benzo-15-crown-5) bipyridyl ligand and new mono- and bis-benzo-15-crown-5 and aza-15-crown-5 bipyridyl ligands containing trans-conjugated olefinic linkages between the crown ethers and the 4,4′-disubstituted 2,2′-bipyridine (bipy) moieties have been synthesised. The corresponding [RuL(bipy)₂][PF₆]₂ and [RuL₃][PF₆]₂ complexes have been prepared and the latter electropolymerized onto optically transparent conducting glass electrodes. Electronic absorption and fluorescence-emission spectroscopic measurements have demonstrated spectrochemical recognition of Group IA and IIA metal cations by the novel functionalized crown ethers both as solution complexes and as polymeric films. The λ_max and ε values for both the low-energy ligand-based π–π* transition and the metal-to-ligand charge transfer band observed for the complexes are sensitive to the binding of sodium and magnesium cations. The spectral measurements further demonstrate the presence of residual unsaturated linkages in the electropolymerized films, providing a technique that could be applied to probe the mechanisms and efficiencies of such electropolymerizations.