The one-electron reduction of triiodide (I-3(-)) by a series of reduced ruthenium polypyridyl compounds was studied in an acetonitrile solution at room temperature using the flash-quench technique. Reductive quenching of the metal-to-ligand charge-transfer excited state of [Ru(bpy)(2)(deeb)](2+), [Ru(deeb)(2)(bpy)](2+), or [Ru(deeb)(3)](2+), where bpy is 2,2'-bipyridine and deeb is 4,4'-(CO2CH2CH3)(2)-2,2'-bipyridine, by iodide generated the reduced ruthenium compounds and diiodide (I-2(center dot-)). Charge recombination of the reduced ruthenium compounds and I-2(center dot-) occurred with rate constants near the calculated diffusion limit of 2.6 x 10(10) M-1 s(-1). The reaction of the reduced ruthenium compounds with I-3(-) was characterized spectroscopically through the addition of I-3(-) into the experimental solution prior to the laser flash. Transient absorption data indicated that I-2(center dot-) was a reaction product of I-3(-) reduction and appeared with an average second-order rate constant of (5.0 +/- 0.6) x 10(9) W-1 s(-1) for all three compounds. The insensitivity of the rate constants for I-3(-) reduction over an 80 meV change in the driving force was unexpected. The relevance of these findings to solar energy conversion within dye-sensitized solar cells is discussed.