Jump to main content
Jump to site search


Unusual near infrared (NIR) fluorescent palladium(ii) macrocyclic complexes containing M–C bonds with bioimaging capability

Author affiliations

Abstract

Near infrared (NIR) luminescent metal complexes are promising probes in bioimaging and biosensing, however they generally suffer from oxygen interference arising from heavy metal effects. We designed new tetradentate macrocyclic benzitripyrrin (C^N^N^N) ligands by combination of M–C bond formation and reducing the π-conjugation to achieve NIR fluorescent Pd complexes (700–1000 nm) with quantum yields up to 14%. To understand the origin of NIR fluorescence, detailed analyses by density functional theory/time-dependent density functional theory (DFT/TDDFT) calculations together with femtosecond and nanosecond transient absorption spectroscopies suggest that M–C bond formation indeed leads to destabilization of the d–d excited state and less effective quenching of emission; and importantly, small spin–orbital coupling (SOC) and the large singlet-triplet energy gap are the primary causes of the non-population of triplet states. Comparison of PdII and PtII analogues shows that the non-radiative channel of the out-plane vibration of the tripyrrin plane effectively quenches the fluorescence of the PtII complex but not the PdII congener. We also demonstrate the proof-of-concept applications of PdII complexes (Pd-1 and Pd-3) encapsulated in silica nanoparticles, in both in vitro and in vivo bioimaging experiments without oxygen interference. Moreover, pH-induced reversible switching of NIR fluorescence was achieved even intracellularly using the Pd complex (Pd-2), which shows the potential to further develop perspective stimuli-responsive NIR materials.

Graphical abstract: Unusual near infrared (NIR) fluorescent palladium(ii) macrocyclic complexes containing M–C bonds with bioimaging capability

Back to tab navigation

Supplementary files

Publication details

The article was received on 13 Aug 2019, accepted on 11 Sep 2019 and first published on 11 Sep 2019


Article type: Edge Article
DOI: 10.1039/C9SC04044G
Chem. Sci., 2019, Advance Article
  • Open access: Creative Commons BY-NC license
    All publication charges for this article have been paid for by the Royal Society of Chemistry

  •   Request permissions

    Unusual near infrared (NIR) fluorescent palladium(II) macrocyclic complexes containing M–C bonds with bioimaging capability

    Y. Yao, C. Hou, Z. Yang, G. Ran, L. Kang, C. Li, W. Zhang, J. Zhang and J. Zhang, Chem. Sci., 2019, Advance Article , DOI: 10.1039/C9SC04044G

    This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material and it is not used for commercial purposes.

    Reproduced material should be attributed as follows:

    • For reproduction of material from NJC:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the Centre National de la Recherche Scientifique (CNRS) and the RSC.
    • For reproduction of material from PCCP:
      [Original citation] - Published by the PCCP Owner Societies.
    • For reproduction of material from PPS:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC.
    • For reproduction of material from all other RSC journals:
      [Original citation] - Published by The Royal Society of Chemistry.

    Information about reproducing material from RSC articles with different licences is available on our Permission Requests page.

Search articles by author

Spotlight

Advertisements