Poly-p-hydroquinone Ethers: Isoenergetic Molecular Wires with Length-Invariant Oxidation Potentials and Cation Radical Excitation Energies.

Typical poly-p-phenylene wires are characterized by strong interchromophoric electronic coupling with redox and optical properties being highly length-dependent. Herein we show that an incorporation of a pair of para-methoxy groups at each p-phenylene unit in poly-p-phenylene wires (i.e., PHEn) changes the nodal structure of HOMO that leads to length-invariant oxidation potentials and cation radical excitation energies. As such, PHEn represents a unique class of isoenergetic wires where hole delocalization mainly occurs via dynamic hopping and thus may serve as an efficient medium for long-range charge transfer. Availability of these wires will allow demonstration of long-range electron transfer via incoherent hopping using donor-bridge-acceptor systems with isoenergetic PHEn-based wires as bridges.