Switchable fluorescence by click reaction of a novel azidocarbazole dye

Abstract

Imaging iseven these daysstill restricted to of a few classes of robust dyes. A demand for switchable tags led us to the design of a new class of pre-fluorophores. We achieved this by using a non-fluorescent N-(4-azidophenyl)-carbazole tag which turns fluorescent by click reaction with alkynes and cyclooctynes.The spectral properties of the labelled dyes were investigated. Our results suggest that a twisted internal charge transfer (TICT) transition is responsible for the emission. DFT calculations and single-crystal X-ray diffraction of selected examples support this explanation. The feasibility of the new dyes for biological application has also been tested via confocal microscopy.Scheme 1 Synthetic route to N-(4-azido-phenyl)-carbazole 1. † Electronic supplementary information (ESI) available: Characterisation, spectra, computation method and X-ray crystallographic information les for compounds 2 and 3 (CIF). CCDC 936576 and 936577. For ESI and crystallographic data in CIF or other electronic format see

Design strategies for bioorthogonal smart probes

“…Quenching via ICT may also be operant in other scaffolds, such as in azide-functionalized BODIPY, benzothiazole, and carbazoles ( 14–16 ), although other factors may be at play. 64–67 …”

Cyclopropenone-caged Sondheimer diyne (dibenzo[a,e]cyclooctadiyne): a photoactivatable linchpin for efficient SPAAC crosslinking

“…12 Diyne 2a has been employed for the cross-coupling of various azide-functionalized substrates from biomolecules to metal – organic frameworks. 12,13 The utility of this method, however, is limited by the low stability of the Sondheimer diyne. In the neat form 2a completely decomposes within two days and exhibits half lifetime of only 10 min in a neutral aqueous solution (1mM in PBS, pH 7.4, r.t.).…”

Bioorthogonal fluorescent labels: a review on combined forces

“…Together with other fluorogenic azido-dyes, this azido-naphthtalimide was also successfully applied in the real time activity measurement of aberrantly activated oncogenic Src kinases in the crude lysate of leukemia cells [88]. Just very recently, an azido-phenyl carbazole(Figure 12, 9)was introduced by Bräse and co-workers [89]. This carbazole derivative was found to be virtually dark, while fluorescent after reaction with alkynes, possessing UV excitability (291-293 nm, various solvents) and visible emission (387-492 nm, various solvents).…”