Department of Organic Chemistry, Weizmann Institute of Science, 76100 Rehovot (Israel).
Chemistry. 2013 Sep 23;19(39):13140-50. doi: 10.1002/chem.201301293. Epub 2013 Aug 9.
The extent of charge delocalization and of conjugation in oligofurans and oligothiophenes was studied by using mixed valence systems comprising oligofurans and oligothiophenes capped at both ends by ferrocenyl redox units. Using electrochemical, spectral, and computational tools, we find strong charge delocalization in ferrocene-capped oligofurans which was stronger than in the corresponding oligothiophene systems. Spectroscopic studies suggest that the electronic coupling integral (H(ab)) is roughly 30-50 % greater for oligofuran-bridged systems, indicating better energy matching between ferrocene units and oligofurans. The distance decay constant (damping factor), β, is similar for oligofurans (0.066 A(-1)) and oligothiophenes (0.070 A(-1)), which suggests a similar extent of delocalization in the bridge, despite the higher HOMO-LUMO gap in oligofurans. Computational studies indicate a slightly larger extent of delocalization in furan-bridged systems compared with thiophene-bridged systems, which is consistent with oligofurans being significantly more rigid and less aromatic than oligothiophenes. High charge delocalization in oligofurans, combined with the previously reported strong fluorescence, high mobility, and high rigidity of oligofuran-based materials makes them attractive candidates for organic electronic applications.
通过使用两端由二茂铁氧化还原单元封端的寡呋喃和寡噻吩混合价系统，研究了寡呋喃和寡噻吩中的电荷离域和共轭程度。使用电化学、光谱和计算工具，我们发现二茂铁封端的寡呋喃中存在很强的电荷离域，比相应的寡噻吩体系更强。光谱研究表明，电子耦合积分（H(ab)）对于寡呋喃桥接系统大致增加了 30-50%，表明二茂铁单元和寡呋喃之间更好的能量匹配。对于寡呋喃（0.066 A(-1)）和寡噻吩（0.070 A(-1)），距离衰减常数（阻尼因子）β相似，这表明尽管寡呋喃中的 HOMO-LUMO 间隙较高，但桥中存在相似程度的离域。计算研究表明，与噻吩桥接系统相比，呋喃桥接系统中的离域程度略大，这与寡呋喃比寡噻吩更刚性和非芳香性一致。寡呋喃中的高电荷离域，结合之前报道的寡呋喃基材料的强荧光、高迁移率和高刚性，使它们成为有机电子应用的有吸引力的候选者。
