Département de chimie moléculaire

Two alternated bimetallic Ru-Fe and Ru-Zn coordination polymers, [{\{}RuII(bpy)2(L2)MII{\}}n]4n+ (M = Fe2+, Zn2+), were synthesized using the [Ru(bpy)2(L2)]2+ (bpy = 2,2' bipyridine) complex as a building block, in which L2 (I) is a bipyridine ligand substituted by two terpyridine sites. The [Ru(bpy)3]2+ like-subunits provide the assemblies with photoredox properties whereas the second metal allows the build-up of the polymer structure by coordination of the free terpyridine units, assocd. with addnl. redox activities. Thin robust films of these metallo supramol. structures can be easily obtained as a coating on electrode surfaces (C, Pt, and ITO) by a simple electrochem. procedure based on an electroreductive pptn. adsorption process. The morphol. of the films was characterized by AFM. Electrochem. and photophys. properties of these coordination polymers were investigated in CH3CN soln. as well as thin films deposited on an electrode. The Ru(II)-Zn(II) film, deposited on a transparent ITO electrode, displays luminescence properties. However, the Ru(II)-Fe(II) film exhibits electrochromic properties under continuous cycling over the FeII/FeIII and RuII/RuIII waves, shifting from reddish dark at the Fe(II)-Ru(II) reduced state to orange-yellow at the Fe(III)-Ru(II) state and to pale green at the more oxidized state Fe(III)-Ru(III). These oxidn. processes can be also driven by visible light. Indeed, upon continuous irradn. of an CH3CN soln. of the Ru-Fe polymer in the presence of a diazonium salt as a sacrificial electron acceptor, the fast quant. one-electron oxidn. of the Fe(II) centers followed by that of the Ru(II) ones occurs, despite the strong quenching of the luminescence of the Ru(II) moieties by the Fe(II) center. The photoinduced oxidn. of the Fe(II) center is still efficient when the Ru(II)-Fe(II) polymer is electrodeposited as a thin film on ITO leading to the storage of an oxidative equiv. on an electrode. [on SciFinder(R)]