Electronic Decay Constant of Carotenoid Polyenes from Single-Molecule Measurements

摘要

Carotenoid polyenes have been used extensively as electron donors in molecular systems that demonstrate photoinduced electron transfer and have recently been found to act as electron shuttles in photosynthesis.Direct measurements of their conductance show that it is ca.7 orders of magnitude higher than that of equivalent-length n-alkanes,as might be expected on theoretical grounds.This high conductivity should correspond to a small value of beta,the electronic decay constant.A lower limit for beta has been inferred from spectroscopic data obtained from intervalence charge-transfer complexes linked by polyenes,but beta has not been measured directly.