Calix[4]arene based 1,3,4-oxadiazole as a fluorescent chemosensor for copper(II) ion detection

A green reaction-based turn-off fluorescence sensor for determination of copper ions: DFT calculations, quenching mechanism, green chemistry metrics, and application in environmental samples

When Cu(II) reacts with ascorbic acid (AA) to form Cu(I), Cu(I) can combine with eosin Y (EY) to form ionic associations, resulting in significant fluorescence quenching of the EY. Based on the turn-off of fluorescence in the chemosensor EY, a green reaction is proposed herein for the detection of Cu(II). The novel detection method for Cu(II) demonstrates simplicity, high sensitivity, and excellent selectivity, rendering it suitable for analyzing environmental samples. A static fluorescence quenching mechanism is validated through the Stern-Volmer relationship, and the thermodynamic parameters of the reaction are explored using a van 't Hoff plot. The reaction mechanism is investigated via fluorescence spectra, absorption spectra, and density-functional theory (DFT) calculations. The probe's green nature is confirmed by applying four green analytical chemistry metrics.

Simple turn-on fluorescent chemosensor for ultrafast and highly selective trace-level detection of Cu2+ ions in aqueous solutions

A benzimidazole-based probe, BIPMA (2-(1H-benzo[d]imidazol-2-yl)-N-(pyridin-2-ylmethyl)aniline), was designed and synthesized to detect Cu2+ ions. BIPMA exhibited a fluorescent "turn-on" mechanism when bound to Cu2+ ions in an acetonitrile/water mixture (5:5, v/v, HEPES 10 mM, pH 7.4) owing to the synergistic effect of the chelation-enhanced fluorescence and internal charge-transfer mechanisms. Moreover, the BIPMA probe effectively detected nanomolar-range concentrations (0-400 nM) of Cu2+ ions in an aqueous system with a detection limit of 4.80 nM; this value is significantly lower than that set by the U.S. Environmental Protection Agency (≈20 μM). Additionally, BIPMA showed an ultrafast response to Cu2+ ions, with a maximum intensity achieved 25 s after adding Cu2+. Furthermore, BIPMA detected Cu2+ ions in solutions with a pH range of 5-11, without being influenced by pH, underscoring its applicability under various physiological conditions. Density functional theory studies revealed that internal charge transfer was responsible for emission. Finally, BIPMA effectively detected Cu2+ ions in real water samples and living cells.

Progress in appended calix[4]arene-based receptors for selective recognition of copper ions

In the past two decades, there has been significant progress in the design and development of synthetic receptors for molecular recognition as they find application in the field of chemical, biological, medical, and environmental sciences. Synthetic receptors based on calix systems appended with fluorogenic and chromogenic groups have gained considerable attention for sensing and recognition of ions and molecules. Copper (Cu2+) is an essential element required in trace amounts in all living organisms to carry out various biological processes. The aim of this review is to summarize advancement in π-conjugated fluorogenic and chromogenic groups appended to calix[4]arene motifs for detection and quantitation of Cu2+ ion. The focus is to present a comprehensive account of extended calix[4]arene systems with different linkers and highlight the unique design and binding characteristics for the recognition and sensing of Cu2+ ions.

A Novel Calix[4]Crown-Based 1,3,4-Oxadiazole as a Fluorescent Chemosensor for Copper(II) Ion Detection

The synthesis and characterization of a novel florescent chemosensor 1 with two different types of cationic binding sites have been reported in this work, which is a calix[4]crown derivative in 1,3-alternate conformation bearing two 2-phenyl-5-(4-dimethylaminopyenyl)-1,3,4-oxadiazole units. The recognition behaviors of 1 in dichloromethane/acetonitrile solution to alkali metal ions (Na+ and K+), alkaline earth metal ions (Mg2+ and Ca2+), and transition metal ions (Co2+, Ni2+, Zn2+, Cd2+, Cu2+, Mn2+, and Ag+) have been investigated by UV-Vis and fluorescence spectra. The fluorescence of 1 might be quenched selectively by Cu2+ due to the photo-induced electron transfer mechanism, and the quenched emission from 1 could be partly revived by the addition of Ca2+ or Mg2+; thus, the receptor 1 might be worked as an on-off switchable fluorescent chemosensor triggered by metal ion exchange.

Supramolecular brush polymers prepared from 1,3,4-oxadiazole and cyanobutoxy functionalised pillar[5]arene for detecting Cu2+

The self-assembly of an A1/A2 disubstituted pillar[5]arene was used to construct a supramolecular brush polymer.

A new class of supramolecular liquid crystals derived from azo calix[4]arene functionalized 1,3,4-thiadiazole derivatives

A new class of bowl-shaped supramolecular liquid crystals (LCs) is described derived from calix[4]arene substituted with 1,3,4-thiadiazole derivatives, inbuilt with Schiff base and ester on the lower rim and with an azo group on the upper rim with an alkyl side chain (–OC₃H₇, –OC₈H₁₇).

Columnar self-assembly, gelation and electrochemical behavior of cone-shaped luminescent supramolecular calix[4]arene LCs based on oxadiazole and thiadiazole derivatives

A new class of blue light-emitting supramolecular liquid crystalline cone or bowl-shaped compounds were synthesized from substituted 1,3,4-oxadiazoles and 1,3,4-thiadiazoles with calix[4]arene derivatives.

Syntheses and Properties of meso-Substituted Porphyrin Mesogens with Triazole Linkages and Peripheral Alkyl Chains

Discotic mesogens P/n-M (n=12, 16, 18, M=2 H, Zn and Cu) bearing a porphyrin core, triazole linkages and peripheral 3,4,5-trialkoxybenzyl units have been synthesized by a click-chemistry approach. The thermal behavior, photophysical properties and morphologies of these compounds were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), XRD, UV and PL, SEM and TEM. These compounds can self-assemble into hexagonal columnar phases in their pure states and form organogels in 1,4-dioxane with unusually flower-like sphere morphology. The supramolecular complexes of P/18-Zn with C₇₀ or 4,7-di-4-pydriyl-2,1,3-benzothadiazole can display hexagonal columnar phases too. Additionally, zinc porphyrin compounds P/n-Zn show binding selectivity to Cu²⁺ among a series of cations in THF/H₂ O.

A one-step synthesized acridine-based fluorescent chemosensor for selective detection of copper(ii) ions and living cell imaging

A highly selective and sensitive fluorescence quenching chemosensor (ACC) for Cu²⁺ detection in HEPES buffer and living cell imaging was developed.