We report the surface growth of oligophenylene molecular wires on Si(111) substrates and their electron-transfer (ET) properties. Iterative wire growth of bipheoylene was achieved Via Pd-catalyzed Negishi reactions for lengths of n(phenyl) = 1, 2, and 12 (d approximate to 5-50 angstrom). The triflato-capped wires were functionalized with vinylferrocene for potentiometric studies. For the oligophenylenes of n(phenyl) = 1, 2, and 4 (wire length d approximate to 5-20 angstrom), there was a strong distance dependence (k(app) = 22.6, 16.0, 8.40 s(-1), respectively), Correlated to beta = 0.07 angstrom(-1). In contrast, longer oligophenylenes for n(phenyl) = 4-12 (d approximate to 20-50 angstrom) displayed a negligible distance dependence with an ET rate of k(app) approximate to 10.0 +/- 1.6 s(-1). These data suggest a distance-dependent tunneling mechanism at short lengths (d < 20 angstrom) and a distance-independent ET at longer lengths (d > 20 angstrom).