Lauer Milena Helmer, Drekener Roberta Lopes, Correia Carlos Roque Duarte, Gehlen Marcelo Henrique
Institute of Chemistry of São Carlos, University of São Paulo, CEP 13560-590, São Carlos, SP, Brazil.
Photochem Photobiol Sci. 2014 Jun;13(6):859-66. doi: 10.1039/c4pp00001c.
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Heck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荧光发射带，在极性溶剂中具有大的斯托克斯位移，并且发射量子产率在0.04至0.71之间变化，这取决于结构和溶剂介质。基态和激发态电子态的偶极矩差异约为12德拜，这归因于双芳基取代马来酰亚胺的大量电荷转移和推挽特性。N-苄基-3,4-双（4-甲氧基苯基）-1H-吡咯-2,5-二酮（化合物5a）在极性溶剂中的荧光衰减是双指数的，具有短（1.3 - 7.6纳秒）和长寿命（11.5 - 13.6纳秒）成分，但在1,4 - 二氧六环和四氢呋喃中衰减变为单指数。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N，N-二甲基甲酰胺中表现出双指数衰减，衰减成分短得多，这种行为表明在激发态存在电荷转移过程与溶剂辅助质子转移相结合。
