作者:Milena Helmer Lauer、Roberta Lopes Drekener、Carlos Roque Duarte Correia、Marcelo Henrique Gehlen
DOI:10.1039/c4pp00001c
日期:2014.6
A series of bisaryl-substituted fluorescent maleimides was synthesized via the Heck arylation. The compounds showed broad fluorescence emission bands in the visible region, a large Stokes shift in polar solvents and emission quantum yields varying from 0.04 to 0.71, depending on the structure and solvent medium. The difference in dipole moments of ground and excited electronic states of about 12 Debye is ascribed to a substantial charge shift and push–pull character of bisaryl-substituted maleimides. The fluorescence decays of N-benzyl-3,4-bis(4-methoxyphenyl)-1H-pyrrole-2,5-dione (compound 5a) are biexponential with short (1.3–7.6 ns) and long lived (11.5–13.6 ns) components in polar solvents, but in 1,4-dioxane and THF the decays become single exponential. On the other hand, N-benzyl-3-(4-methoxyphenyl)- 4-(4-hydroxyphenyl)-1H-pyrrole-2,5-dione (compound 5b) exhibited a biexponential decay in DMSO and in DMF with much shorter decay components, and such behavior indicated a charge shift process combined with solvent assisted proton transfer in the excited state.
通过赫克芳基化反应合成了一系列双芳基取代的荧光马来酰亚胺。这些化合物在可见光区域显示出宽广的荧光发射带,在极性溶剂中具有较大的斯托克斯偏移,发射量子产率因结构和溶剂介质的不同而从 0.04 到 0.71 不等。基态和激发态电子的偶极矩相差约 12 Debye,这归因于双芳基取代马来酰亚胺的大量电荷转移和推拉特性。在极性溶剂中,N-苄基-3,4-双(4-甲氧基苯基)-1H-吡咯-2,5-二酮(化合物 5a)的荧光衰减为双指数衰减,有短寿命(1.3-7.6 ns)和长寿命(11.5-13.6 ns)两种成分,但在 1,4-二氧六环和四氢呋喃中,衰减为单指数衰减。另一方面,N-苄基-3-(4-甲氧基苯基)-4-(4-羟基苯基)-1H-吡咯-2,5-二酮(化合物 5b)在二甲基亚砜和 DMF 中呈现双指数衰减,衰减分量更短,这种行为表明激发态中存在电荷转移过程和溶剂辅助质子转移。