A series of fluorenylazomethine dyads and triads were prepared by simple condensation between the corresponding amine and aldehyde fluorene derivatives. These compounds were prepared as model compounds for investigating the effects of substitution and electronic groups on both the electrochemical properties and fluorescence quantum yields. It was found that the oxidation potential could be decreased by both incorporating electron donating groups and increasing the degree of conjugation. It was further found that alkylation in the fluorene’s 9-position increased the azomethine degree of conjugation by forcing all the fluorene moieties to be coplanar with the azomethine bonds to which they are attached. Meanwhile, reversible radical cation behaviour was possible by substituting the terminal 2,2′-positions with atoms other than hydrogen. The radical cation was theoretically found to be distributed evenly across the fluorene, corroborating the reversible anodic behaviour with 2,2′-substitution. The fluorescence quantum yields of the azomethines were not found to be dependent on substitution. This was because the azomethine fluorescence was found to be quenched relative to their precursors regardless of substitution. The fluorescence could be restored at both low temperature and by acid protonation.
通过相应的胺和醛芴衍生物之间的简单缩合,制备了一系列芴基氮甲基二元和三元化合物。制备这些化合物是为了研究取代基和电子基团对电化学性质和荧光量子产率的影响。研究发现,通过加入电子捐赠基团和增加共轭程度,可以降低氧化电位。研究还发现,在芴的 9 位上进行烷基化,可迫使所有芴分子与所连接的偶氮甲基键共面,从而提高偶氮甲基键的共轭度。同时,通过用氢原子以外的原子取代末端 2,2′ 位,可实现可逆的自由基阳离子行为。理论上,自由基阳离子均匀地分布在芴中,这证实了 2,2′ 取代后的可逆阳极行为。偶氮甲基的荧光量子产率与取代无关。这是因为无论取代与否,相对于其前体,偶氮甲基荧光都会被淬灭。在低温和酸质子化条件下,荧光都可以恢复。