Dinitrophenyl and NBD platforms based fluorescent sensors for nanomolar detection of zinc ions: Synthesis, zinc ions sensing and DFT studies

Tauqir Ahmad, Safwat Abdel-Azeim, Sardaraz Khan, Nisar Ullah*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The design and synthesis of two new fluorescent probes based on dinitrophenyl (1) and 7-nitrobenz-2-oxa-1,3-diazole (2) platforms is reported. Both probes, containing bis(pyridin-2-ylmethyl)amine as a receptor unit can efficiently detect zin ions (Zn2+) in aqueous solution, with limit of detections of 124 nM and 1.06 µM, respectively. Probe 1 and 2 led to 3-fold and 2.4-fold fluorescent enhancements, respectively, with the addition of Zn2+ which suggested that working mechanism of these probes is based on the inhibition of the photoinduced electron transfer from the electron donating receptor towards the excited fluorophore. Studying binding stoichiometry by job's plot suggested 1:1 complexation between the probe and Zn2+. Moreover, the formation of probes-Zn2+ complexes was validated by both FT-IR and 1H NMR wherein marked changes in the absorption frequencies as well as distinct downfield shifts in the resonance peaks of pyridine function along with the [sbnd]CH2[sbnd] group linked directly to the tertiary nitrogen of the DPA unit were observed. Density functional theory (DFT) calculations suggested that the electronic density of the HOMO in 1 was concentrated on the linker between DPA and dinitrophenyl, whereas the density of the LUMO was concentrated on dinitrophenyl moiety. Upon Zn2+ binding, the electronic density in HOMO and LUMO become more delocalized. However, in case of probe 2 the delocalization of electronic density does not appreciably occur. Based on DFT simulations, both sensors form thermodynamic stable complexes with Zn2+ ions. However, sensor 2 exhibited slightly better binding preference toward Zn2+ as compared to 1. The PET based probes exhibited good selectivity to detect Zn2+ in the presence of a variety of competing metal cations. These sensors have higher sensitivity and would be able to detect chronic level of Zn2+ in the freshwater (>1.84 μM) as permitted by the US EPA.

Original languageEnglish
Article number113151
JournalInorganic Chemistry Communication
Volume170
DOIs
StatePublished - Dec 2024

Bibliographical note

Publisher Copyright:
© 2024 Elsevier B.V.

Keywords

  • 7-Nitrobenz-2-oxa-1,3-diazole
  • Bis(pyridin-2-ylmethyl)amine
  • DFT calculations
  • Fluorescent sensors
  • Photoinduced electron transfer
  • Zinc ion

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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