Towards functionalized poly(terthiophenes): regioselective synthesis of oligoether-substituted bis(styryl)sexithiophenes.
A variety of new bis(oligo(oxyethylene)styryl)sexithiophenes have been prepared by chemical oxidation of ether-substituted styrylterthiophenes with FeCl3. In all cases dimers are formed in high yields, rather than the expected polymers. In addition, although three different regioisomers can potentially be formed from such an oxidation, the isolable products are shown to consist of only the head-to-head regioisomer. Theoretical calculations on alkoxystyrylterthiophenes show that this can be understood in terms of an uneven electron spin density distribution at the two alpha-positions available for polymerization. Electron density calculations on the resulting head-to-head alkoxystyrylsexithiophenes show that the spin density is concentrated in the core of the molecule rather than at the alpha-positions, a result that explains the absence of significant amounts of higher oligomers.
Grant
Daina K
DK
New Zealand Institute for Crop & Food Research Ltd., Private Bag 11600, Palmerston North 5301, New Zealand. grantd@crop.cri.nz
Jolley
Kenneth W
KW
Officer
David L
DL
Gordon
Keith C
KC
Clarke
Tracey M
TM