A colorimetric probe for the real-time naked eye detection of cyanide and hydroxide ions in tap water: experimental and theoretical studies

A pH-Sensitive Fluorescent Chemosensor Turn-On Based in a Salen Iron (III) Complex: Synthesis, Photophysical Properties, and Live-Cell Imaging Application

pH regulation is essential to allow normal cell function, and their imbalance is associated with different pathologic situations, including cancer. In this study, we present the synthesis of 2-(((2-aminoethyl)imino)methyl)phenol (HL1) and the iron (III) complex (Fe(L1)2Br, (C1)), confirmed by X-ray diffraction analysis. The absorption and emission properties of complex C1 were assessed in the presence and absence of different physiologically relevant analytes, finding a fluorescent turn-on when OH- was added. So, we determined the limit of detection (LOD = 3.97 × 10-9 M), stoichiometry (1:1), and association constant (Kas = 5.86 × 103 M-1). Using DFT calculations, we proposed a spontaneous decomposition mechanism for C1. After characterization, complex C1 was evaluated as an intracellular pH chemosensor on the human primary gastric adenocarcinoma (AGS) and non-tumoral gastric epithelia (GES-1) cell lines, finding fluorescent signal activation in the latter when compared to AGS cells due to the lower intracellular pH of AGS cells caused by the increased metabolic rate. However, when complex C1 was used on metastatic cancer cell lines (MKN-45 and MKN-74), a fluorescent turn-on was observed in both cell lines because the intracellular lactate amount increased. Our results could provide insights about the application of complex C1 as a metabolic probe to be used in cancer cell imaging.

Quinoline based thiosemicarbazones as colorimetric chemosensors for fluoride and cyanide ions and DFT studies

High toxicity and extensive accessibility of fluoride and cyanide ions in diverse environmental media encouraged attention for scheming well-organized probes for their detection. Keeping in mind we have designed and synthesized thiosemicarbazone-based chemosensors RB-1, RB-2 and RB-3 for the detection of fluoride and cyanide ions. The structural elucidation of the synthesized chemosensors is done by employing different analytical techniques including nuclear magnetic resonance and electronic absorption specrtoscopies. Admirable detection limit, binding constant and fast response time (2 s) to F⁻ and CN⁻ ions enlarged the applications of these chemosensors. Additional confirmation of the sensing ability of these chemosensors is derived from DFT and TDDFT calculations with M06/6-311G(d,p) method by performing FMO, UV–Vis, QTAIM and global reactivity parameters elucidation. Overall results point out that investigated chemosensors are suitable candidates for sensing the F⁻ ions. These chemosensors were successfully applied to detect F⁻ ions in a commercial toothpaste sample.

An ESIPT-ICT steered naphthylthioic-based ionic probe with dual emissive channels exhibiting CHEF and CHEQ effects

A naphthylthioic-based emissive probe (M) bearing a hydroxyl and amine group was designed and synthesized via a one-step Schiff base reaction process. The probe was characterized spectroscopically using ¹H NMR, UV-Vis and fluorescence spectrophotometers. The probe turned out to be spectroscopically and colorimetrically selective and sensitive to multiple cations and anions. Interestingly, the probe displayed characteristics of excited-state intramolecular proton transfer (ESIPT)-driven dual emissive channels; experiencing fluorescence enhancement upon the molar additions of Al³⁺ as well as the anions used, events presumably ascribed to chelation fluorescence enhancement (CHEF), hydrogen bonding and deprotonation effects. Moreover, the fluorometric titration with Hg²⁺ resulted in ratiometric spectral behaviors of M, with the disappearance of the peak at 450 nm, concomitant with the appearance of a new peak at 520 nm, distinguished by a clear isosbestic point, the same behaviors exhibited by Sn²⁺ and Ag⁺ analytes towards M. The introduction of all other cations used, resulted in fluorescence quenching, attributable to chelation enhanced fluorescence quenching (CHEQ), thereby inhibiting the ESIPT process. The experiments were all carried out in the aqueous environment medium of DMSO–H₂O (9 : 1) at ambient temperature. Theoretical density functional theory calculations were carried out to gain insight into the interaction of M with cations and anions, and their influence on the HOMO–LUMO energy gaps.

A naphthylthioic-based emissive probe (M) bearing a hydroxyl and amine group was designed and synthesized via a one-step Schiff base reaction process.

A chromo-fluorogenic probe for detecting water traces in aprotic solvents based on C2-symmetry dianthrimide-hydroxide complexes: experimental and theoretical studies

A C₂-symmetry dianthrimide based probe (D) and its hydroxide complex (D-OH) are reported as a chromo-fluorogenic sensor for rapid and sensitive detection of trace amounts of water in polar aprotic solvents. Based on intramolecular charge transfer in the excited state, the pink-coloured probe binds with the hydroxide ions to induce a colorimetric response of the resulting complex (D-OH), green in colour. The hydroxide based complex is used as a H₂O or moisture sensor, tested in DMF and DCM, due to its high instability in moisture-containing organic solvents and paper materials/fabrics. The probe exhibits higher sensitivity towards pure H₂O in DMSO with the LOD measured at 0.0067% v/v, perhaps even lower, in DMF (LOD = 0.100% v/v) and DCM (LOD = 0.013% v/v). The dissociation of OH^- from D in the presence of H₂O is responsible for the colorimetric and fluorometric responses. The litmus test paper strips prepared by adsorbing or coating them with the D-OH complex in DMSO could not be entirely achieved in an open system, due to the highly unstable state of the complex in the presence of water traces or the atmospheric moisture accumulated in the paper materials. The complex D-OH is also highly suspected to compete for adsorbed water in silica gel crystals in desiccators, due to its high affinity towards water molecules. The experimental studies were complemented by theoretical calculations using the Spartan'14 software package, and the computed data are in good agreement with the spectral data.