LONG-DISTANCE ELECTRON-TRANSFER THROUGH RODLIKE MOLECULES WITH CUBYL SPACERS

Rates of intramolecular electron transfer have been measured through cubanes. Pulse radiolysis was used to study the reactions B-Cu(n)N half arrow right over half arrow left BCu(n)N-, where B - (4-biphenylyl), N = (2-naphthyl), and Cu(n) is the; composed of n = 1-3 1,4-cubyl oligomers. Electronic couplings, V, for these reactions were found to decrease exponentially with increasing distance, V(R) = V(R0) exp[-0.5 beta-R], with beta = 0.90 angstrom-1. While the electron-transfer rates in these cubanes are a factor of 10 larger than in similar compounds with spacers based on cyclohexane, the distance dependence is almost identical to that for the cyclohexyl-type molecules, beta = 0.94 angstrom-1. The unusual properties of the cubanes enhanced the electron-transfer rates but did not lead to a large difference in distance dependence.