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Fluorescence from bisaryl-substituted maleimide derivatives†
Milena Helmer Lauer,Roberta Lopes Drekener,Carlos Roque Duarte Correia,Marcelo Henrique Gehlen
Photochemical & Photobiological Sciences Pub Date : 03/31/2014 00:00:00 , DOI:10.1039/C4PP00001C
Abstract

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.

Graphical abstract: Fluorescence from bisaryl-substituted maleimide derivatives
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