A sensitive zinc probe operating via enhancement of excited-state intramolecular charge transfer

Org Biomol Chem. 2022 Sep 28;20(37):7439-7447. doi: 10.1039/d2ob01296k.

Abstract

Novel highly sensitive fluorescent probes for zinc cations based on the diketopyrrolopyrrole scaffold were designed and synthesized. Large bathochromic shifts (≈80 nm) of fluorescence are observed when the Zn2+-recognition unit (di-(2-picolyl)amine) is bridged with the fluorophore possessing an additional pyridine unit able to participate in the coordination process. This effect originates from the dipolar architecture and the increasing electron-withdrawing properties of the diketopyrrolopyrrole core upon addition of the cation. The new, greenish-yellow emitting probes, which operate via modulation of intramolecular charge transfer, are very sensitive to the presence of Zn2+. Introduction of a morpholine unit in the diketopyrrolopyrrole structure induces a selective six-fold increase of the emission intensity upon zinc coordination. Importantly, the presence of other divalent biologically relevant metal cations has negligible effects and typically even at a 100-fold higher concentration of Mg2+/Zn2+, the effect is comparable. Computational studies rationalize the strong bathochromic shift upon Zn2+-complexation. Decorating the probes with the triphenylphosphonium cation and morpholine unit enables selective localization in the mitochondria and the lysosome of cardiac H9C2 cells, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amines
  • Cations, Divalent
  • Fluorescent Dyes* / chemistry
  • Ketones
  • Morpholines
  • Pyridines
  • Pyrroles
  • Spectrometry, Fluorescence
  • Zinc* / chemistry

Substances

  • Amines
  • Cations, Divalent
  • Fluorescent Dyes
  • Ketones
  • Morpholines
  • Pyridines
  • Pyrroles
  • diketopyrrolopyrrole dye
  • Zinc