Gated electron sharing within dynamic naphthalene diimide-based oligorotaxanes

Abstract

The controlled self-assembly of well-defined and spatially ordered π-systems has attracted considerable interest because of their potential applications in organic electronics. An important contemporary pursuit relates to the investigation of charge transport across noncovalently coupled components in a stepwise fashion. Dynamic oligorotaxanes, prepared by template-directed methods, provide a scaffold for directing the construction of monodisperse one-dimensional assemblies in which the functional units communicate electronically through-space by way of π-orbital interactions. Reported herein is a series of oligorotaxanes containing one, two, three and four naphthalene diimide (NDI) redox-active units, which have been shown by cyclic voltammetry, and by EPR and ENDOR spectroscopies, to share electrons across the NDI stacks. Thermally driven motions between the neighboring NDI units in the oligorotaxanes influence the passage of electrons through the NDI stacks in a manner reminiscent of the conformationally gated charge transfer observed in DNA. Birds of a feather flock together: Mutually π-stacked small-molecule naphthalene diimide (NDI) [24]crown-8 derivatives self-assemble dynamically on a repeating -(CH2CH2NH2+CH 2)-template to afford the stepwise evolution of discrete-length oligorotaxanes, which are shown to communicate electronically through their co-facially interacting π-surfaces, sharing electrons across linear arrays containing one, two, three, and four NDI units as determined by cyclic voltammetry and EPR/ENDOR spectroscopies. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.