Detection of water content in alcohol solvents over Al3+ induced colorimetric and NIR-fluorescent sensor based on isophorone-phenylamine

Advances on fluorescence chemosensors for selective detection of water

Water, although an important part of everyday life, is acts as one of the most significant contaminants in various applications such as biomedical monitoring, chemical production, petroleum-based fuel and food processing. In fact, the presence of water in other solvents is a huge concern. For the quantification of trace water content, different methods such as Karl-Fischer, electrochemical, nuclear magnetic resonance, chromatography, and thermogravimetric analysis have been used. Although every technique has its own benefit, each one suffers from several drawbacks that include high detection costs, lengthy procedures and specialized operations. Nowadays, the development of fluorescence-based chemical probes has become an exciting area of research for the quick and accurate estimation of water content in organic solvents. A variety of chemical processes such as hydrolysis reaction, metal ions promoted oxidation reaction, suppression of the -C═N isomerization, protonation and deprotonation reactions, and molecular aggregation have been well researched in the last few years for the fluorescent detection of trace water. These chemical processes eventually lead to different photophysical events such as aggregation-induced emission (AIE), aggregation-induced emission enhancement (AIEE), aggregation-caused quenching (ACQ), fluorescent resonance energy transfer (FRET), charge transfer, photo-induced electron transfer (PET), excited state intramolecular proton transfer (ESIPT) that are responsible for the detection. This review presents a summary of the fluorescence-based chemosensors reported in recent years. The design of water sensors, sensing mechanisms and their potential applications are reviewed and discussed.

Recent advances in the synthesis and utility of thiazoline and its derivatives

Thiazolines and their derivatives hold significant importance in the field of medicinal chemistry due to their promising potential as pharmaceutical agents. These molecular entities serve as critical scaffolds within numerous natural products, including curacin A, thiangazole, and mirabazole, and play a vital role in a wide array of physiological reactions. Their pharmacological versatility encompasses anti-HIV, neurological, anti-cancer, and antibiotic activities. Over the course of recent decades, researchers have extensively explored and developed analogs of these compounds, uncovering compelling therapeutic properties such as antioxidant, anti-tumor, anti-microbial, and anti-inflammatory effects. Consequently, thiazoline-based compounds have emerged as noteworthy targets for synthetic endeavors. In this review, we provide a comprehensive summary of recent advancements in the synthesis of thiazolines and thiazoline-based derivatives, along with an exploration of their diverse potential applications across various scientific domains.

Pyrene-based fluorescent chemosensor for rapid detection of water and its applications

This manuscript introduces a pyrene-based Schiff base L by reacting pyrenecarboxaldehyde with 2-aminothiazole in equimolar ratio. The ligand L was characterized by various spectral data and single crystal. The water sensing ability of L was examined in different organic solvents. The weakly emissive L in DMSO showed a fluorescence enhancement upon the addition of water. The water-induced fluorescence enhancement of L was occurred due to the combined effect of aggregation-induced emission (AIE) phenomenon and suppression of photo-induced electron transfer (PET) process. Using L, the water in DMSO can be detected down to 0.50 wt% with a quantification limit of 1.52 wt%. The analytical novelty of the developed sensor L was validated by detecting moisture in a variety of raw food products.

A simple hydrazone probe for recognition of Al3+ and PPi and its applicability in lysosomal imaging

A simple hydrazone probe (1) was designed and synthesized for the successive detection of Al³⁺ and pyrophosphate (PPi) in almost 100% buffer environment. The probe provided O₂N donor set for chelation with Al³⁺, leading to a distinct fluorescence boost at 510 nm. The in-situ formed 1-Al³⁺ complex detected PPi with an "on-off" behavior. The detection limits for Al³⁺ and PPi were 35.7 nM and 76 nM, respectively. Benefiting from the existence of morpholine as lysosome-targeting group, probe 1 was successfully applied to the detection of Al³⁺ and PPi in lysosomes.

A NIR fluorescent sensor based on thiazoline-isophorone with low cytotoxicity in living cells for Hg2+ detection through ICT associated hydrogen bonding effect

Mercury (Hg) is a toxic pollutant and may cause serious health and environmental threats even at low concentrations. Thus, sensitive, efficient, and accurate techniques for the detection of Hg²⁺ ions in biological systems are in particular demand. In the current paper, a new, red emitting fluorescence probe (THI) based on electron deficient dicyanovinyl, electron-rich diethylamino, and receptor thiazoline toward Hg²⁺ has been developed. It has been determined that the recognition behavior of the probe toward Hg²⁺ is reversible with S^2-. The probe not only shows perfect selectivity toward Hg²⁺ with a low detection limit over a series of metal ions, but it also displays positive solvato-chromism among the tested solvents via modulation of intramolecular energy transfer from the diethylamino to a dicyanovinyl moiety. Furthermore, it has been shown that the probe can be applied as a fluorescent probe for visualizing Hg²⁺ in living HeLa cells through a confocal laser scanning microscope. Also, the probe THI has not shown any toxic effect in cervical cancer and epithelial cells. Thus, the probe demonstrates high promise for Hg²⁺ detection in biomarker screening, disease diagnosis, and clinical medicine with low cytotoxicity.

Excited-State Dynamics of a meta-Dimethylamino Locked GFP Chromophore as a Fluorescence Turn-on Water Sensor†

Strategic incorporation of a meta-dimethylamino (-NMe₂ ) group on the conformationally locked green fluorescent protein (GFP) model chromophore (m-NMe₂ -LpHBDI) has drastically altered molecular electronic properties, counterintuitively enhancing fluorescence of only the neutral and cationic chromophores in aqueous solution. A ˜200-fold decrease in fluorescence quantum yield of m-NMe₂ -LpHBDI in alcohols (e.g., MeOH, EtOH and 2-PrOH) supports this GFP-derived compound as a fluorescence turn-on water sensor, with large fluorescence intensity differences between H₂ O and ROH emissions in various H₂ O/ROH binary mixtures. A combination of steady-state electronic spectroscopy, femtosecond transient absorption, ground-state femtosecond stimulated Raman spectroscopy (FSRS) and quantum calculations elucidates an intermolecular hydrogen-bonding chain between a solvent -OH group and the chromophore phenolic ring -NMe₂ and -OH functional groups, wherein fluorescence differences arise from an extended hydrogen-bonding network beyond the first solvation shell, as opposed to fluorescence quenching via a dark twisted intramolecular charge-transfer state. The absence of a meta-NMe₂ group twisting coordinate upon electronic excitation was corroborated by experiments on control samples without the meta-NMe₂ group or with both meta-NMe₂ and para-OH groups locked in a six-membered ring. These deep mechanistic insights stemming from GFP chromophore scaffold will enable rational design of organic, compact and environmentally friendly water sensors.