Substituted 9-Diethylaminobenzo[a]phenoxazin-5-ones (nile red analogues): Synthesis and photophysical properties

Mick Hornum*, Mads W. Mulberg, Maria Szomek, Peter Reinholdt, Jonathan R. Brewer, Daniel Wüstner, Jacob Kongsted, Poul Nielsen

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Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Abstrakt

Nile Red is a benzo[a]phenoxazone dye containing a diethylamino substituent at the 9-position. In recent years, it has become a popular histological stain for cellular membranes and lipid droplets due to its unrivaled fluorescent properties in lipophilic environments. This makes it an attractive lead for chemical decoration to tweak its attributes and optimize it for more specialized microscopy techniques, e.g., fluorescence lifetime imaging or two-photon excited fluorescence microscopy, to which Nile Red has never been optimized. Herein, we present synthesis approaches to a series of monosubstituted Nile Red derivatives (9-diethylbenzo[a]phenoxazin-5-ones) starting from 1-naphthols or 1,3-naphthalenediols. The solvatochromic responsiveness of these fluorophores is reported with focus on how the substituents affect the absorption and emission spectra, luminosity, fluorescence lifetimes, and two-photon absorptivity. Several of the analogues emerge as strong candidates for reporting the polarity of their local environment. Specifically, the one- and two-photon excited fluorescence of Nile Red turns out to be very responsive to substitution, and the spectroscopic features can be finely tuned by judiciously introducing substituents of distinct electronic character at specific positions. This new toolkit of 9-diethylbenzo[a]-phenoxazine-5-ones constitutes a step toward the next generation of optical molecular probes for advancing the understanding of lipid structures and cellular processes.

OriginalsprogEngelsk
TidsskriftJournal of Organic Chemistry
Vol/bind86
Udgave nummer2
Sider (fra-til)1471–1488
ISSN0022-3263
DOI
StatusUdgivet - 2021

Bibliografisk note

Funding Information:
We acknowledge the Independent Research Fund Denmark—Natural Sciences (DFF-FNU) for financial support (Grant ID: DFF-7014-00050B).

Publisher Copyright:
© XXXX American Chemical Society

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

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