Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Oct 3;28(19):6921.
doi: 10.3390/molecules28196921.

Theoretical Investigation on the "ON-OFF" Mechanism of a Fluorescent Probe for Thiophenols: Photoinduced Electron Transfer and Intramolecular Charge Transfer

Yuxi Wang  1   2 , Meng Zhang  1 , Wenzhi Li  1   2 , Yi Wang  1 , Panwang Zhou  2
Affiliations

Theoretical Investigation on the "ON-OFF" Mechanism of a Fluorescent Probe for Thiophenols: Photoinduced Electron Transfer and Intramolecular Charge Transfer

Yuxi Wang et al. Molecules. .

Abstract

In this study, the sensing mechanism of (2E,4E)-5-(4-(dimethylamino)phenyl)-1-(2-(2,4dinitrophenoxy)phenyl)penta-2,4-dien-1-one (DAPH-DNP) towards thiophenols was investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). The DNP group plays an important role in charge transfer excitation. Due to the typical donor-excited photo-induced electron transfer (d-PET) process, DAPH-DNP has fluorescence quenching behavior. After the thiolysis reaction between DAPH-DNP and thiophenol, the hydroxyl group is released, and DAPH is generated with the reaction showing strong fluorescence. The fluorescence enhancement of DAPH is not caused by an excited-state intramolecular proton transfer (ESIPT) process. The potential energy curves (PECs) show that DAPH-keto is less stable than DAPH-enol. The frontier molecular orbitals (FMOs) of DAPH show that the excitation process is accompanied by intramolecular charger transfer (ICT), and the corresponding character of DAPH was further confirmed by hole-electron and interfragment charge transfer (IFCT) analysis methods. Above all, the sensing mechanism of the turn-on type probe DAPH-DNP towards thiophenol is based on the PET mechanism.

Keywords: ESIPT; d-PET; frontier molecular orbital; thiophenol.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; collection, analyses, or interpretation of data; writing of the manuscript, or decision to publish the results.

Figures

Scheme 1
Scheme 1
Sensing mechanism of probe DAPH-DNP towards thiophenols.
Figure 1
Figure 1
The optimized structures of DAPH-DNP in the S0 (a), LE (S1) (b), and CT (S2) states (c). The labeling of atomic color: O: red; C: blue; H: white; N: yellow, the bond length in Å, the dihedral angle in degrees.
Figure 2
Figure 2
Excitation processes of DAPH-DNP. Molecular orbitals are given in blue and red iso-surfaces, holes and electrons are given in blue and green iso-surfaces, respectively (ωB97XD/TZVP/IEFPCM).
Figure 3
Figure 3
The IFCT analyzing the electron excitation process of DAPH-DNP molecular fragments. (a) The amount of electron transfer between fragments from S0 to S1 (b) and S2 states (c) (ωB97XD/TZVP/IEFPCM).
Figure 4
Figure 4
The ωB97XD/TZVP/IEFPCM calculated energies of DAPH-DNP showing the PET mechanism. The red bars: S2 state.
Figure 5
Figure 5
The optimized geometries of DAPH in the S0 and S1 states. The labeling of atomic color: O: red; C: blue; H: white; N: yellow, the bond length in Å, the angles are in degrees.
Figure 6
Figure 6
The calculated IR spectra of the DAPH in the spectral region of the O1–H2 stretching band calculated.
Figure 7
Figure 7
The PECs of the S0 and S1 states for DAPH along with the O1–H2 bond length (ωB97XD/TZVP/IEFPCM).
Figure 8
Figure 8
Excitation processes of DAPH. Molecular orbitals are given in blue and red iso-surfaces, holes and electrons are given in blue and green iso-surfaces, respectively (ωB97XD/TZVP/IEFPCM).
Figure 9
Figure 9
The DAPH molecular fragments electron excitation process analyzed by the IFCT (a) and the amount of inter-fragment electron transfer from the S0 to S1 States (b) (ωB97XD/TZVP/IEFPCM).
Figure 10
Figure 10
The cLR-ωB97XD/TZVP/IEFPCM calculated energies of DAPH showing the ICT mechanism.
See this image and copyright information in PMC

References

    1. Ji H.-F., Shen L., Zhang H.-Y. Theoretical Reinvestigation of Opposite Electronic Effects on Bond Lengths in Thiophenols and Thiophenolic Radicals. J. Struct. Chem. 2005;46:347–351. doi: 10.1007/s10947-006-0052-y. - DOI
    1. dos Santos D.J.V.A., Newton A.S., Bernardino R., Guedes R.C. Substituent Effects on O–H and S–H Bond Dissociation Enthalpies of Disubstituted Phenols and Thiophenols. Int. J. Quantum Chem. 2008;108:754–761. doi: 10.1002/qua.21522. - DOI
    1. Wang H., Wu X., Yang S., Tian H., Liu Y., Sun B. A Rapid and Visible Colorimetric Fluorescent Probe for Benzenethiol Flavor Detection. Food Chem. 2019;286:322–328. doi: 10.1016/j.foodchem.2019.02.033. - DOI - PubMed
    1. Zhang Y., Hao Y., Ma X., Chen S., Xu M. A Dicyanoisophorone-Based Highly Sensitive and Selective near-Infrared Fluorescent Probe for Sensing Thiophenol in Water Samples and Living Cells. Environ. Pollut. 2020;265:114958. doi: 10.1016/j.envpol.2020.114958. - DOI - PubMed
    1. Xiao M.-M., Ren H., Liu T.-Z., Li Z.-Y., Wang J.-Z., Miao J.-Y., Zhao B.-X. Two Fluorescent Turn-on Probes for Detecting Thiophenols in Environmental Water and in Living Cell Imaging. Microchem. J. 2022;175:107220. doi: 10.1016/j.microc.2022.107220. - DOI

LinkOut - more resources