Near-infrared fluorescent dyes with large Stokes shifts: light generation in BODIPYs undergoing excited state intramolecular proton transfer

Abstract

Novel BODIPYs undergoing excited state intramolecular proton transfer are reported. The molecules afford NIR emission with a large Stokes shift and possess a free hydroxyl unit that is easy to functionalize, allowing the dyes to be exploited as a valuable scaffold in probe design.

Organic Near‐Infrared Luminescent Materials Based on Excited State Intramolecular Proton Transfer Process†

“…HBT is another most well‐studied ESIPT‐active material with green emission, [ 58 ] based on which several NIR luminescent molecules have been reported as shown in Figure 3. [ 59‐62 ] For compounds 9 and 10 , high red‐shift emissions were achieved by introducing ionic type strong acceptor groups in C 3 position of HBT with conjugated olefins as connectors. BODIPY possesses excellent photophysical properties such as high quantum yield, easy synthesis and modification, which make it promising for its application in near‐infrared materials.…”

“…reported an ESIPT‐based near‐infrared BODIPY (NIR‐BODIPY, compound 11 ). [ 61 ] The ESIPT process of NIR‐BODIPY is shown in Figure 4a. ESIPT of synthetic compounds is facilitated by the presence of hydrogen bonds in pre‐existing compounds.…”

“…synthesized BOD‐Cys (compound 13 ) and BOD‐thiol (compound 14 ) for monitoring thiols by masking the hydroxyl group of NIR‐BODIPY. [ 61 ] The structures of BOD‐Cys and BOD‐thiol are shown in Figure 4b. It was found that the designed probe exhibited a near‐infrared response to thiols at 740 nm, and the probe had a large Stokes shift (5005 cm –1 ).…”

“…(a, c, d, f, g reproduced with permission. [ 61 ] Copyright 2017 The Royal Society of Chemistry. e, g reproduced with permission.…”

A molecular design strategy toward enzyme-activated probes with near-infrared I and II fluorescence for targeted cancer imaging

“…Currently, several NIR probes to detect enzyme activities have been built based on cyanine and rhodamine scaffolds 7. However, these known NIR probes suffer from undesirable small Stokes shifts, which generally lead to severe cross-talk between the excitation and emission spectra that significantly compromises sensitive detection and accurate analysis 8. Thus, the advance of cancer-biomarker imaging requires innovations to establish novel fluorescent scaffolds that are excitable and emit in the NIR region with large Stokes shifts.…”