Control of Intermolecular Photoinduced Electron Transfer in Deoxyadenosine‐Based Fluorescent Probes

• Published in: Chemistry : a European journal Vol. 27; no. 4; pp. 1364 - 1373
• Main Authors: Le, Hoang‐Ngoan, Brazard, Johanna, Barnoin, Guillaume, Vincent, Steve, Michel, Benoît Y., Leonard, Jérémie, Burger, Alain
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 18-01-2021; Wiley-VCH Verlag
• Subjects: Acidification; Adenine; Chemical Sciences; Chemistry; Complex formation; Conjugates; Deoxyadenosine; deoxyadenosine probes; DNA probes; Dyes; Electrode potentials; Electron transfer; Electrons; Fluorescence; Fluorescence spectroscopy; Fluorescent indicators; ground-state complexes; or physical chemistry; Oxidation; photoinduced electron transfer; Probes; push–pull dyes; Theoretical and; photoinduced electron transfer; push-pull dyes; ground-state complexes; fluorescence; deoxyadenosine probes; Ground-state complex; deoxyadenosine; turn-on; push-pull dye
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202003456

In this work, we report on the Photoinduced Electron Transfer (PET) reaction between a donor (adenine analogue) and an acceptor (3‐methoxychromone dye, 3MC) in the context of designing efficient fluorescent probes as DNA sensors. Firstly, Gibbs energy was investigated in disconnected donor–acceptor systems by Rehm‐Weller equation. The oxidation potential of the adenine derivative was responsible for exergonicity of the PET reaction in separated combinations. Then, the PET reaction in donor‐π‐acceptor conjugates was investigated using steady‐state fluorescence spectroscopy, acid‐mediated PET inhibition and transient absorption techniques. In conjugated systems, PET is a favorable pathway of fluorescent quenching when an electron‐rich adenine analogue (d7A) was connected to the fluorophore (3MC). We found that formation of ground‐state complexes even at nm concentration range dominated the dye photophysics and generated poorly emissive species likely through intermolecular PET from d7A to 3MC. On the other hand, solution acidification disrupts complexation and turns on the dye emission. Bridging an electron‐poor adenine analogue with high oxidation potential (8 d7A) to 3MC presenting low reduction potential is another alternative to prevent complex formation and produce highly emissive monomer conjugates.
Yin and yang PET: intramolecular photoinduced electron transfer (PET) is often responsible for fluorescence quenching of many dyes. Herein, a different scenario has emerged for our push‐pull nucleosides. These fluorophores preform a ground‐state complex with a head‐to‐tail arrangement evidencing an intermolecularly controllable process. Ultimately, these results could help reconsider several useful dyes as well as guide the development of advanced adenine‐based probes.