We report the measurement of distance- and temperature-dependent rate constants for charge separation in capped hairpins in which a stilbene hole acceptor and hole donor are separated by A3Gn diblock polypurine sequences consisting of 3 adenines and 1-19 guanines. The longer diblock systems obey the simplest model for an unbiased random walk, providing a direct measurement of khop = 4.3 × 109 s -1 for a single reversible G-to-G hole hopping step, somewhat faster than the value of 1.2 × 109 s-1 calculated for A-tract hole hopping. The temperature dependence for hopping in A 3G13 provides values of Eact = 2.8 kcal/mol and A = 7 × 109 s-1, consistent with a weakly activated, conformationally gated process.
ASJC Scopus subject areas
- Colloid and Surface Chemistry