Rational Design of Push–Pull Fluorene Dyes: Synthesis and Structure–Photophysics Relationship. Issue 30 (15th June 2016)

• Record Type: Journal Article
• Authors: Shaya, Janah; Fontaine‐Vive, Fabien; Michel, Benoît Y.; Burger, Alain
• Is Part Of: Chemistry. Volume 22:Issue 30(2016)
• Page Start: 10627
• Page End: 10637
• Publication Date: 2016-06-15
• Subjects: Buchwald–Hartwig amination -- charge transfer -- fluorescent probes -- push–pull fluorenes -- structure–photophysics relationship; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201600581
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Our work surveyed experimental and theoretical investigations to construct highly emissive D –π–A (D=donor, A=acceptor) fluorenes. The synthetic routes were optimised to be concise and gram‐scalable. The molecular design was first rationalised by varying the electron‐withdrawing group from an aldehyde, ketotriazole or succinyl to methylenemalonitrile or benzothiadiazole. The electron‐donating group was next varied from aliphatic or aromatic amines to saturated cyclic amines ranging from aziridine to azepane. Spectroscopic studies correlated with TD‐DFT calculations provided the optimised structures. The selected push–pull dyes exhibited visible absorptions, significant brightness, important solvatofluorochromism, mega‐Stokes shifts (>250 nm) and dramatic shifts in emission to the near‐infrared. The current library includes the comprehensive characterization of 16 prospective dyes for fluorescence applications. Among them, several fluorene derivatives bearing different conjugation anchors were tested for coupling and demonstrated to preserve the photophysical responses once further bound. Abstract : Building a fluorescent LEGO box : Based on a fluorene scaffold, the design, robust synthesis, and characterization of a library of dyes is reported. The dyes have varying push–pull strengths, important solvatofluorochromism properties, and suitable anchoring groups for conjugation. DFT calculations support an enhanced intramolecular charge transfer from which their near‐IR emission originates. The Hammett prediction model provides a tool to anticipate the photophysical properties. Translation abstract: Nous avons synthétisé des dérivés du fluorène comportant un groupe donneur (D) et accepteur (A) de type D–π–A très brillants et présentant différents points d′ancrage qui ne modifient pas la photophysique une fois conjugués. Leur conception rationnelle est basée sur une modification de la partie acceptrice A en criblant différents groupements électro‐attracteurs tels que formyle, cétotriazolyle, succinyle, méthylènemalonitrile et benzothiadiazolyle. Quant à la partie donneuse, diverses amines aliphatiques, aromatiques et cycliques saturées de tension de cycle variée (de l′aziridine à l′azépane) furent introduites. Des études spectroscopiques combinées à des calculs TD‐DFT ont permis d′identifier les fluorophores aux propriétés les plus remarquables. Les meilleures sondes absorbent dans le visible et démontrent une extrême brillance, un solvatofluorochromisme important et des déplacements de Stokes (>250 nm) conduisant à des émissions dans le proche IR. Cette librairie comprend ainsi 16 sondes prometteuses pour des applications en fluorescence.