Department of Chemistry and the Macromolecular Science and Engineering Program, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA.
J Org Chem. 2012 Oct 19;77(20):9298-303. doi: 10.1021/jo301744s. Epub 2012 Oct 3.
Oligomers containing the new fused-ring heterocyclic conjugated building block thieno[3,2-b]furan were synthesized, and the effects associated with furan ring substitution into fused-ring oligothiophenes on the electronic properties and solid-state structure were assessed. A series of four-ring oligomers which vary in the degree of furan ring substitution and the regiochemistry of placement were synthesized via Stille cross-coupling and oxidative homocoupling strategies. The electronic properties of these oligomers were studied by UV-vis absorption and fluorescence spectroscopies. Substitution of furan rings at the terminal positions yields oligomers with a narrower HOMO-LUMO gap relative to the all-thiophene analogue 2,2'-bithieno[3,2-b]thiophene, and incorporation of furan rings at the interior positions results in oligomers with an increase in rigidity and a higher fluorescence quantum yield. Packing motifs of the oligomers were determined using single crystal X-ray diffraction. In contrast to the herringbone crystal packing observed for nonfused oligothiophenes, oligofurans, thiophene-furan hybrid oligomers, and the all-thiophene analogue 2,2'-bithieno[3,2-b]thiophene, all three regioisomers derived from the dimerization of thieno[3,2-b]furan arrange in a π-stacked packing motif in the solid state.
合成了含有新的稠环杂环共轭构建块噻吩并[3,2-b]呋喃的低聚物，并评估了呋喃环取代稠合噻吩低聚物对电子性质和固态结构的影响。通过 Stille 交叉偶联和氧化齐聚策略合成了一系列四环低聚物，它们在呋喃环取代程度和位置的区域化学上有所不同。通过紫外-可见吸收和荧光光谱研究了这些低聚物的电子性质。与全噻吩类似物 2,2'-联噻吩[3,2-b]噻吩相比，末端取代呋喃环的低聚物具有较窄的 HOMO-LUMO 能隙，而在内部位置引入呋喃环的低聚物则具有增加的刚性和更高的荧光量子产率。使用单晶 X 射线衍射确定了低聚物的堆积模式。与未稠合的噻吩低聚物、噻吩-呋喃杂低聚物和全噻吩类似物 2,2'-联噻吩[3,2-b]噻吩观察到的鱼骨状晶体堆积相反，噻吩并[3,2-b]呋喃二聚体的三种区域异构体在固态中以π堆积堆积模式排列。
