Abstract
Addition of [Ru(bpy)3][PF6]2 to [(C6H13)4N]4[S2 Mo18O62] in CH3CN resulted in the formation of analytically pure [Ru(bpy)3]2[S2Mo18 O62]. Insolubility in CH3CN and solubility in DMF allow solid state and solution phase electrochemical data to be compared. Voltammetric studies of [Ru(bpy)3]2[S2Mo18O62] adhered to a glassy carbon electrode surface and placed in contact with CH3CN (0.1 M Bu4NPF6) indicate diffusion of ions within the solid occurs rapidly in order to achieve charge neutralisation required for oxidation of the [Ru(bpy)3]2+ cation and reduction of the [S2Mo18O62]4- anion. Mass increases on the electrode surface (detected by the electrochemical quartz crystal microbalance method) accompany both oxidation and reduction processes, eqns. (i)-(iv). Cyclic voltammetry of 0.2 mM [Ru(bpy)3]2[S2Mo18O62] in DMF (0.1 M Bu4NPF6) reveals one reversible oxidation (E1/2r + 791 mV) and two reversible fully solution phase diffusion controlled reduction reactions (E1/2r -33 and -310 mV vs. Fc+/Fc), corresponding to the [Ru(bpy)3]2+/3+ and [S2Mo18O62]4-/5- and [S2Mo18O62]5-/6- charge transfer processes, respectively. With 1 mM [Ru(bpy)3]2[S2Mo18O62] in DMF (0.1 M Bu4NPF6) precipitation on the electrode surface occurs on scanning to potentials more negative than the initial reduction process, due to formation of [Bu4N]2[Ru(bpy)3]2 [S2Mo18O62]. Enhanced levels of surface based processes are also observed in the voltammetry of [Ru(bpy)3]2[S2Mo18O62] in DMF (0.01 M Bu4NPF6), corresponding to precipitation of [Bu4N][Ru(bpy)3]2[S2 Mo18O62] and [Ru(bpy)3]2[S2Mo18 O62][PF6] on the electrode surface. Data imply that mixed cation salts are more soluble than those containing only [Ru(bpy)3]2+ in all redox levels.
Original language | English |
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Pages (from-to) | 1076-1082 |
Number of pages | 7 |
Journal | Dalton |
Volume | 7 |
Issue number | 7 |
DOIs | |
Publication status | Published - 21 Jun 2001 |