摘要:

Introductionπ-Conjugated oligomers are regarded as the ideal model compounds for understanding the electro-optical properties of π-conjugated polymers. Impressive advances in research have been achieved on π-conjugated materials1and have led towards a better understanding of the relationship between the desired functional properties and the enhanced supramolecular structure, by making use of its well-defined chemical structure and conjugation length.2Highly ordered local structures are the prerequisite for obtaining electronic properties such as high carrier mobility. Controlled organisation of π-conjugated oligomers has been achieved by using a suitable solvent–nonsolvent mixture,3thermotropic and lyotropic liquid crystallinity4,5hydrogen bonding motifs,6,7and by block copolymers.8Efficient macromolecular assembly of oligomers will become critically important to achieve new applications, molecular electronics providing the most outstanding prospect.9Surfactant interactions are often used in nature to assemble molecules into large systems, such as membranes. This methodology has inspired chemists to synthesise a variety of artificial surfactants,e.g.amphiphiles, to construct well-defined assemblies in water and at the air–water interface.10Remarkably, lipophilic interactions have rarely been applied in the supramolecular organisation of π-conjugated oligomers in contrast to amphiphilic π-conjugated polymers.11Recently, the self-assembly of α,ω-disubstituted sexithiophenes in butanol and water has been reported.12Alternating α-oligothiophene blocks with poly(ethylene oxide) blocks have been synthesised and the oligothiophenes aggregate in a 83% water–dioxane mixture in a face-to-face manner.13Oligo(p-phenylenevinylene) (OPV) has been functionalisedwith ethylene glycol chains14and pendant ethylene glycol dendrons15showing superstructures in THF–water14aand water14band at the air–water interface, respectively. Monolayers have also recently been constructed from amphiphilic OPVs containing a pyridine or diaminotriazine headgroup to obtain controllable organisation at the air–water interface.16The Langmuir–Blodgett technique can be used to prepare light-emitting diodes (LED) that show linear polarisation of the emitted light.17Here, we report the synthesis of two novel chiral (bola)amphiphilic OPV's (Scheme 1,OPV1andOPV2) as an extension of our work on the fully aliphatic OPV oligomers of different lengths.18AmphiphileOPV1consists of a hydrophobic OPV tetrameric core with, at one end a hydrophobic trialkoxybenzene wedge and, at the other end, a hydrophilic tris[tetra(ethylene oxide)]benzene wedge. BolaamphiphileOPV2contains a hydrophobic pentameric OPV core, substituted with two hydrophilic tris[tetra(ethylene oxide)]benzene wedges at both ends. We have chosen chiral amphiphiles because a stereocenter in the side-chain has been proven to be a very informative probe in studying the expression of chirality at the supramolecular level.19The organisation of the OPV amphiphiles has been studied at the air–water interface and in water.A) LiAlH4, 8 h, 0 °C. B) DCM, SOCl2, 1 h. C) PO(Et)3, 8 h, 160 °C. D and H) DMF–THF,4, KOC(CH3)3, 8 h. E and G) DMF,n-BuLi, −10 °C, 1 h. F) DMF, KOC(CH3)3, diethyl {2,5-bis[(S)-2-methylbutoxy]-4-bromobenzyl}phosphonate, 3 h, rt.

ISSN:1472-779X    

DOI:10.1039/b103966k

出版商:RSC    

年代:2001

数据来源: RSC