Dynamic Coordination between a Triphenylamine-Functionalized Salicylaldehyde Schiff Base and a Copper(II) Ion.

The coordination between a ligand and a metal is a spontaneous and uncontrollable process. In this Article, we successfully observe the formation of metal coordination in a triphenylamine-functionalized salicylaldehyde Schiff base with a copper(II) ion. The ligand TPA-Py first reacts with Cu2+ in a stepwise process to afford the dynamic complex TPA-Py@Cu2+ ([ligand]:[Cu2+] = 1:1), which further reacts with an extra copper(II) ion to afford 2TPA-Py@4Cu2+ with the following stepwise (or cumulative) stability constants: K1 = 4.0694 × 103 and K2 = 1.0761 × 106, respectively. The entire metal coordination process can be visualized, and the coordination mode of the probe toward copper was further evaluated by ultraviolet-visible/fluorescence spectra, single-crystal X-ray diffraction, density functional theory calculations, high-resolution mass spectra, and nuclear magnetic resonance spectroscopic titrations. Compound TPA-Py exhibited excellent sensitivity and specificity toward copper(II) ions in THF/water media with a low limit of detection of 2.687 × 10-7 mol L-1. In addition, TPI-An-Py can be applied to the detection of Cu2+ in real samples with satisfactory recoveries in the range of 100-112% in lake water and 98-101% in tap water. This Article not only reports an excellent fluorescence probe for copper(II) ion detection but also presents an instance for more fully understanding the metal coordination process.

A Turn-On Fluorescent Chemosensor for Cyanide Ion Detection in Real Water Samples.

We have designed and synthesized a novel simple colorimetric fluorescent probe with aggregation-induced emission (AIE) properties. Probe 5-(4-(diphenylamine)phenyl) thiophen-2-formaldehyde W exhibited a turn-on fluorescent response to cyanide ion (CN-), which induces distinct visual color changes. Probe W exhibited a highly selective and sensitive ratiometric fluorescence response for the detection of CN- over a wide pH range (4-11) and in the presence of common interferents. The linear detection of CN- over the concentration range of 4.00-38.00 µM (R 2 = 0.9916, RSD = 0.02) was monitored by UV-Vis absorption spectrometry (UV-Vis) with the limit of detection determined to be 0.48 µM. The linear detection of CN- over the concentration range of 8.00-38.00 µM was examined by fluorescence spectrophotometry (R 2 = 0.99086, RSD = 0.031), and the detection limit was found to be 68.00 nM. The sensing mechanisms were confirmed by 1H NMR spectroscopic titrations, X-ray crystallographic analysis, and HRMS. Importantly, probe W was found to show rapid response, high selectivity, and sensitivity for cyanide anions in real water samples, over the range of 100.17∼100.86% in artificial lake water and 100.54∼101.64% in running water by UV-Vis absorption spectrometry, and over the range of 99.42∼100.71% in artificial lake water and 100.59∼101.17% in running water by fluorescence spectrophotometry. Importantly, this work provides a simple and effective approach which uses an economically cheap and uncomplicated synthetic route for the selective, sensitive, and quantitative detection of CN- ions in systems relevant to the environment and health.

Twisted Schiff-base macrocycle showing excited-state intramolecular proton-transfer (ESIPT): assembly and sensing properties.

A Schiff-base macrocyclic host (MH) showing ESIPT and AIEE is reported for the first time; the fluorescent macrocycle exhibited good pH tolerance and could serve as a probe for Cu2+ and Fe3+ ion sensing and removal. In addition, a series of size-tunable nanoparticles was fabricated by the self-assembly of free MH and its coordination complex with Fe3+ in THF/water solution.