Laboratory of Organic Chemistry, ETH Zurich, Hönggerberg, HCI, CH-8093 Zurich, Switzerland.
J Org Chem. 2013 Mar 1;78(5):1760-7. doi: 10.1021/jo301194y. Epub 2012 Jul 27.
Symmetrically and unsymmetrically electron-donor-substituted octacyano[4]dendralenes were synthesized and their opto-electronic properties investigated by UV/vis spectroscopy, electrochemical measurements (cyclic voltammetry (CV) and rotating disk voltammetry (RDV)), and electron paramagnetic resonance (EPR) spectroscopy. These nonplanar push-pull chromophores are potent electron acceptors, featuring potentials for first reversible electron uptake around at -0.1 V (vs Fc(+)/Fc, in CH2Cl2 + 0.1 M n-Bu4NPF6) and, in one case, a remarkably small HOMO-LUMO gap (ΔE = 0.68 V). EPR measurements gave well-resolved spectra after one-electron reduction of the octacyano[4]dendralenes, whereas the one-electron oxidized species could not be detected in all cases. Investigations of the radical anions of related donor-substituted 1,1,4,4-tetracyanobuta-1,3-diene derivatives revealed electron localization at one 1,1-dicyanovinyl (DCV) moiety, in contrast to predictions by density functional theory (DFT) calculations. The particular factors leading to the charge distribution in the electron-accepting domains of the tetracyano and octacyano chromophores are discussed.
对称和非对称的电子给体取代的八氰基[4]树状大分子被合成，并通过紫外可见光谱、电化学测量（循环伏安法（CV）和旋转圆盘伏安法（RDV））和电子顺磁共振（EPR）光谱研究了它们的光电性质。这些非平面推挽生色团是有效的电子受体，其第一对可逆电子吸收电位约为-0.1 V（相对于 Fc(+)/Fc，在 CH2Cl2 + 0.1 M n-Bu4NPF6 中），在一种情况下，HOMO-LUMO 能隙（ΔE = 0.68 V）非常小。EPR 测量在八氰基[4]树状大分子的一次还原后给出了分辨率良好的光谱，而在所有情况下都无法检测到一次氧化的物种。对相关供体取代的 1,1,4,4-四氰基丁二烯衍生物的自由基阴离子的研究表明，电子定域在一个 1,1-二氰基乙烯基（DCV）部分，这与密度泛函理论（DFT）计算的预测相反。讨论了导致四氰基和八氰基生色团的电子接受域中电荷分布的特殊因素。
