Synthesis and Properties of Functionalized Oligo(arylene) Molecular Wires with Thiolated Termini: Competing Thiol-Au and Nitro-Au Assembly
作者：Xianshun Zeng, Changsheng Wang, Andrei S. Batsanov, Martin R. Bryce, Joanna Gigon, Barbara Urasinska
關鍵字：molecular wire, assembly
論文來源：期刊
具體來源：J. Org. Chem. 2010, 75, 130–136
發(fā)表時間：2010年
We report the synthesis by Suzuki cross-coupling methodology of oligo(arylene) molecular wires with protected thiolates at both termini and a central electron-acceptor unit (3,5-dinitrofluorenone, compounds 10-12) or an electron-donor unit [9-(1,3-dithiol-2-ylidene)fluorene, compounds 14-17] in the backbone. Core reagents are 2,7-dibromo-3,5-dinitrofluorenone 7 (obtained by nitration of 2,7-dibromofluorenone) and 2,7-dibromo-9-(4,5-dimethyl-1,3-dithiol-2-ylidene)fluorene 13. The solution electrochemical redox properties of these oligo(arylene) derivatives have been studied.The reduction CVs of the dinitrofluorenone-containing molecules display three reversible/quasireversible couples yielding, sequentially, radical anion, dianion, and radical trianion species, e.g., for 11 E1red -1.02 V (vs. Ag/Agþ in THF). The 1,3-dithiol-2-ylidene unit imparts good electron donor properties tomolecules 14, 15, and16 with radical cation formation observed atEox ca. 0.65V(vs.Ag/Agþ inDCM).We also report studies on the assembly of 11 and 15 on gold substrates. Current-voltage (I-V) characteristics and X-ray photoelectron spectra of the monolayers reveal that 11 assembles via competing S-Au and NO2-Au interactions.This unusual phenomenon is ascribed to the very electron deficient dinitrofluorenone core of 11 weakening the S-Au interaction. An important conclusion is that thiolated molecules which possess strongly electron-withdrawing core units, especially those containing nitro groups, may not be suitable for controlled assembly in junctions. In contrast, 15 assembles via conventional S-Au interactions.