Synthesis of donor-σ-perylenebisimide-acceptor molecules having PEG swallowtails and sulfur anchors.

Donor-σ-Acceptor (D-σ-A) molecules, arrayed in a monolayer between electrodes, can serve as molecular rectifiers. Using perylene-3,4,9,10-tetracarboxylic bisimide (PBI) as the acceptor allows the attachment of the donor group to one imide nitrogen and a solubilizing swallowtail, normally a long (e.g., C(19)) alkane connected at midchain, on the other. Such an alkyl tail facilitates the formation of Langmuir-Blodgett (LB) monolayers. We have employed several modified swallowtails to make new D-σ-A molecules: poly(ethylene glycol) (PEG) swallowtails with 6 ether oxygens or with 4 ether oxygens to promote hydrophilicity in orienting LB monolayers, and alkyl swallowtails ending with sulfur anchors (thioacetate, thiol, or methyl disulfide) to stabilize attachment of the D-σ-A molecules to gold electrodes. The preparation and characterization of D-σ-A molecules containing combinations of these swallowtails with pyrene, ferrocene, and tetramethylphenylenediamine donor groups is described.