Département de chimie moléculaire

One of the bipyridines of a [Ru(bpy)₃]²⁺ core has been substituted at its 5 position by a terpyridine chelating unit through an ether bridge. The modification has only a minor influence on the photophys. and electrochem. properties of the Ru(II) complex. This metallo-ligand (C1) is used to obtain two trimetallic structures [RuII-CoIII-RuII]⁷⁺ and [RuII-FeII-RuII]⁶⁺ in soln. by complexation of the corresponding metallic ion to the terpyridine site. Under irradn., an efficient intramol. electron transfer process occurs in [RuII*-CoIII-RuII]7+ with a kinetic rate const. of 9 × 10⁶ s^-1 resulting in the formation of [RuIII-CoII-RuII]⁷⁺. In the presence of a sacrificial electron donor, continuous irradn. leads to the reduced species [RuII-CoII-RuII]6+. On the other hand, [RuII*-FeII-RuII]⁶⁺ follows a deactivation pathway through an energy transfer process with a rate const. of 2 × 10⁸ s^-1. This energy transfer is not total and can be short-circuited in the presence of an external electron acceptor to form the oxidized [RuII-FeIII-RuII]⁷⁺. Based on these results in soln., C1 has been used in a stepwise approach to construct two photoelectrodes on ITO taking advantage of the strong self-assembling interaction between phosphonates with ITO surface and terpyridine ligands with first row transition metals. The luminescence lifetimes of the resulting dyads on surface are drastically lowered compared to the systems in soln. ITO/[CoIII-RuII]⁵⁺ behaves as a photoanode in presence of TEOA as sacrificial electron donor and ITO/[FeII-RuII]4+ as a photocathode in presence of ArN+2 as sacrificial electron acceptor. The photocurrent magnitude depends on the coverage value and increases linearly with the power of the irradn. light, proving the good photostability of these ITO-dyads modified surfaces. Assocn. of both photoelectrodes in a photoelectrochem. cell would result in a gain of 0.8 V. [on SciFinder(R)]