New insights into the sensing mechanism of a phosphonate pyrene chemosensor for TNT

Abstract

As security needs have increased, mechanism investigation has become of high importance in the development of new sensitive and selective chemosensors for chemical explosives. This study details a theoretical investigation of the sensing mechanism of a new phosphonate pyrene chemosensor for trinitrotoluene (TNT), suggesting a different interaction mode between the probe and TNT from the one previously reported. The invalidity of the mechanism of binding TNT through intermolecular hydrogen bonds was proved using the Gibbs free energy profile and 1H NMR analysis. Frontier molecular orbitals (FMOs) analysis was used to show that photo-induced electron transfer (PET) is the underlying mechanism behind the luminescence quenching of the probe upon exposure to TNT, the rationality of which was further confirmed by the recording of a high charge transfer rate. We also found the existence of an energy level crossing between the local excited (LE) state and charge transfer (CT) state of a complex of the probe and TNT, which was confirmed using energy profile calculations along the linearly interpolated internal coordinate (LIIC) pathway.

Electron Transfer Facilitated by π–π Stacking during the Nitrobenzene Recognition Process of an MOF Sensor

“…13−15 Recently, Han and co-workers investigate the TNT detection mechanism of two pyrenebased sensors. 41,42 π−π stacking, in both cases, is found to exist between the sensor and the analyte, which plays a key role during the detecting process. The hydrogen bonding interaction also plays crucial roles in the photo-physical process of organic dyes and sensors.…”

“…π–π stacking is a fundamental weak interaction which exists extensively in DNA, G-quadruplex, graphene, and organometallic compounds. It is reported to facilitate electron transfer during the photo-excitation process of the DNA and G-quadruplex, which is responsible for photo-induced damages. − Recently, Han and co-workers investigate the TNT detection mechanism of two pyrene-based sensors. , π–π stacking, in both cases, is found to exist between the sensor and the analyte, which plays a key role during the detecting process. The hydrogen bonding interaction also plays crucial roles in the photo-physical process of organic dyes and sensors. − In 2020, Hidalgo-Rosa and co-workers performed a series of insightful investigations on the luminescence sensing mechanism of MOF-based sensors. , By exploring the sensing mechanism for aniline and nitrobenzene, the effects of hydrogen bonding interactions are clarified.…”

A Theoretical Study on the Fluorescence Signal Sensing of a colorimetric ClO‐ chemosensor

“…However, it is rather difficult to experimentally and accurately determine the energy levels and the molecular orbitals that involved in these physical mechanisms, which therefore hinders our deep understanding of the signal sensing process and the performance prediction of chemosensors . As a supplement to the experimental techniques, the density functional theory and time‐dependent density functional theory (DFT and TDDFT) are suitable for in‐depth studying of the ICT, PET and FRET related mechanisms by providing detailed and direct information on geometries, energies, orbitals and spectra of chemosensors and other key molecule structures …”

Pyrene-Based Chemosensor for Picric Acid—Fundamentals to Smartphone Device Design

“…Recently, research toward the development of portable fluorimeters and smartphone-based fluorescence sensing and imaging platforms is progressing to meet the real world demand. , The mechanism of sensing involves the interaction of the explosives with the fluorophores resulting in alterations of the fluorescence intensity, wavelength, and lifetime. − Hitherto, various fluorophores are reported in the literature for sensing explosives which include small molecules, conjugated polymers, supramolecules, aggregation-induced emission (AIE) active fluorescent materials, and metal nanoclusters. − Detection of nitro explosives through various fluorescent sensing mechanisms have been widely explored using polyaromatic hydrocarbons (PAHs) such as anthracene and pyrene derivatives. For instance, detection of trinitrotoluene (TNT) using pyrene derivatives was reported through the following mechanisms including π–π stacking interactions and photoinduced electron transfer (PET) . In addition, these derivatives have also been explored as fluorophores for the detection of PA. , Moreover, pyrene derivatives offering both OFF–ON and ON–OFF fluorescence sensing was reported for specific recognition of PA in conjunction with the colorimetric changes .…”

“…For instance, detection of trinitrotoluene (TNT) using pyrene derivatives was reported through the following mechanisms including π−π stacking interactions 31 and photoinduced electron transfer (PET). 32 In addition, these derivatives have also been explored as fluorophores for the detection of PA. 33,34 Moreover, pyrene derivatives offering both OFF−ON and ON−OFF fluorescence sensing was reported for specific recognition of PA in conjunction with the colorimetric changes. 35 However, most of the reported pyrene derivatives are hydrophobic in nature, limiting their application for real-time sensing in aqueous medium.…”