Polymeric and supramolecular arrays for directional energy and electron transport over macroscopic distances

Abstract

There are many important practical consequences of long-range photoinduced electron transfer: many photosensitive biological systems, and most proposed light-responsive molecular electronics devices, operate through photoinduced electron transfer over distances significantly greater than a single molecule. Furthermore, several technological applications require devices employing ordered arrays. For example, molecular shift registers have been described in detail by Hopfield and co-workers, although the experimental difficulties attendant with the construction of such complex systems have not yet been addressed adequately. Thus, construction of three-dimensional arrays which could control the directional movement of electrons over macroscopically large distances is an important objective for both basic and applied science. For several years, this research group has focused on methods to prepare and characterize supramolecular (often polymeric) arrays capable of spatial exploitation of the charge separation induced by light absorption. Here, three macroscopically separate blocks in a polymeric array are arranged sequentially along a backbone whose terminus is chemically bonded to a fixed probe. The component units of each of these blocks would themselves be photoactive or electroactive and would be arranged along an increasing or decreasing energy gradient so as to provide an anisotropic driving force for charge separation. The practical construction graded arrays for energymore » transfer requires that several significant problems be solved.« less