Fluorescent sensing film decorated with ratiometric probe for visual and recyclable monitoring of Cu2

Fluorescent response mechanism based on ESIPT and TICT of novel probe H2QJI: A TD-DFT investigation

Recently, synthesized N-linked-disalicylaldehyde H2QJI probes have been used to detect heavy metal ions in the experiment conveniently. Nevertheless, there needs to be a more in-depth examination of the excited state intramolecular proton transfer (ESIPT) mechanism and photophysical properties of the probe. This work remedied it based on quantum chemistry calculations. We contained due hydrogen bond (O1-H2 ⋯ N3 and O4-H5 ⋯ O6) and then analyzed bond parameters, IR vibration spectra, and non-covalent interaction. The bond strength is enhanced under photoexcitation, and the former is significantly stronger. The calculated electron spectra are in agreement with the experimental values. The results of the S0 and S1 potential energy curves and IRC calculations also confirm the unique ESIPT behavior, which isan excited stated stepwise double proton transfer. The fluorescence, internal conversion, and intersystem crossing rate of KD molecules (twisted-, double proton transfer) were calculated respectively to reveal the radiative and non-radiative pathways. It proved that the corresponding spectra are not obtained since the electrons are mainly deactivated by the ISC (S1->T1). Furthermore, the interfragment charge transfer (IFCT) approach indicates that the molecule possesses twisted intramolecular charge transfer (TICT) characteristics, which lead to the quenching of fluorescence introduction.

Recent Advances in Photoswitchable Fluorescent and Colorimetric Probes

In recent years, significant advancements have been made in the research of photoswitchable probes. These probes undergo reversible structural and electronic changes upon light exposure, thus exhibiting vast potential in molecular detection, biological imaging, material science, and information storage. Through precisely engineered molecular structures, the photoswitchable probes can toggle between "on" and "off" states at specific wavelengths, enabling highly sensitive and selective detection of targeted analytes. This review systematically presents photoswitchable fluorescent and colorimetric probes built on various molecular photoswitches, primarily focusing on the types involving photoswitching in their detection and/or signal response processes. It begins with an analysis of various molecular photoswitches, including their photophysical properties, photoisomerization and photochromic mechanisms, and fundamental design concepts for constructing photoswitchable probes. The article then elaborates on the applications of these probes in detecting diverse targets, including cations, anions, small molecules, and biomacromolecules. Finally, it offers perspectives on the current state and future development of photoswitchable probes. This review aims to provide a clear introduction for researchers in the field and guidance for the design and application of new, efficient fluorescent and colorimetric probes.

Synthesis and Application of Salicylhydrazone Probes with High Selectivity for Rapid Detection of Cu2

Using the aldehyde amine condensation procedure and the triphenylamine group as the skeleton structure, the new triphenylamine-aromatic aldehyde-succinylhydrazone probe molecule DHBYMH was created. A newly created acylhydrazone probe was structurally characterized by mass spectrometry (MS), NMR, and infrared spectroscopy (FTIR). Fluorescence and UV spectroscopy were used to examine DHBYMH's sensing capabilities for metal ions. Notably, DHBYMH achieved a detection limit of 1.62 × 10-7 M by demonstrating exceptional selectivity and sensitivity towards Cu2+ ions in an optimum sample solvent system (DMSO/H2O, (v/v = 7/3); pH = 7.0; cysteine (Cys) concentration: 1 × 10-4 M). NMR titration, high-resolution mass spectrometry analysis, and DFT computation were used to clarify the response mechanism. Ultimately, predicated on DHBYMH's reversible identification of Cu2+ ions in the presence of EDTA, a molecular logic gate was successfully designed.

Multi-targeted fluorescent probes for detection of Zn(II) and Cu(II) ions based on ESIPT mechanism

With the rapid development of industry, it is pretty critical to detect the heavy metals. Recently, the 2-(2-hydroxyphenyl) benzothiazole derivatives with different numbers of rotatable phenyl m (m = 1,2,3) fluorescent probes HL^m were synthesized. However, the theoretical analysis of the mechanism was still missing. In this work, we have systematically researched the mechanisms of excited state intramolecular proton transfer (ESIPT) and the detection of Cu(II), Zn(II) ions for the hydrogen-bond system HL^m though quantum chemistry methods. By bond parameters and the minimum energy pathways analyses, the proton of this system was probed directly transfer without barrier. Bond parameters, real space function at bond critical point, the frontier molecular orbital, electron spectra and orbital interaction diagram were carried to elucidate response to Cu(II), Zn(II) ions. In addition, comparing the Gibbs free energy variation of the complexation reaction between fluorescent probes and ions, it can be proved that the number of rotatable benzene rings affects the response ability of the probe to target ions.

A Novel D-π-A Type Fluorescent Probe for Cu2+ Based on Styryl-Pyridinium Salts Conjugating Di-(2-picolyl)amine (DPA) Units

A novel D-π-A type fluorescent probe L(NO₃) for Cu (II) sensing was designed and fully characterized. The probe consists of a styryl-pyridine cation fluorescent group and a di-(2-picolyl)amine (DPA) receptor unit, which are linked by a phenyl group to form an electron donor-π-acceptor (D-π-A) conjugate system, especially the introduction of a nitrate counter anion for significantly enhanced water solubility of the probe. Fluorescence titration studies of the probe L(NO₃) showed a higher selectivity for Cu²⁺ than other metal ions, and the emission spectrum was strongly quenched upon binding. The competitive binding assay and the low detection limit (0.932 µM) showed that the probe L(NO₃) had strong anti-interference ability and excellent Cu²⁺ detection performance. The binding ratio of probe L(NO₃) and Cu²⁺ was determined from Job's plot to be 1:1, which is consistent with the results obtained from X-ray crystal structures. Meanwhile, the probe showed instantaneous chemical reversibility when titrated with EDTA solution, indicating potential recycling properties of the probe. In addition, the design of inexpensive fluorescent test strips can perform the on-site and real-time detection Cu²⁺ with a color recognition application.

Recent development in fluorescent probes for copper ion detection

Abstract:

Copper is the third most common heavy metal and an indispensable component of life. Variations of body copper levels, both structural and cellular, are related to a number of disorders; consequently, pathophysiological importance of copper ions demands the development of sensitivity and selective for detecting these organisms in biological systems. In recent years, the area of fluorescent sensors for detecting copper metal ions has seen revolutionary advances. Consequently, closely related fields have raised awareness of several diseases linked to copper fluctuations. Further developments in this field of analysis could pave the way for new and innovative treatments to combat these diseases. This review reports on recent progress in the advancement of three fields of fluorescent probes; chemodosimeters, near IR fluorescent probes, and ratiometric fluorescent probes. Methods used to develop these fluorescent probes and the mechanisms that govern their reaction to specific analytes and their applications in studying biological systems, are also given.

2-(2-(Fluorosulfonyloxy)phenyl)benzoxazole

The fluorosulfate derivatives of benzoxazole attract attention since benzoxazole-based compounds have a wide range of biological activities, and the ability of the –SO2F group to react with various functional groups makes it possible to synthesize various new derivatives. The new 2-(2-(fluorosulfonyloxy)phenyl)benzoxazole (2) has been synthesized by the SuFEx click reaction in a two-chamber reactor. Compound 2 is the first example of a benzoxazole derivative with a fluorosulfate-containing substituent at position two of the benzoxazole heterocycle. The anti-cancer potency of 2 was evaluated in silico using molecular docking. The docking results suggest that title compound 2 is of great interest for further studies as a possible anaplastic lymphoma kinase inhibitor.