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@4Cu(2+) with the following stepwise (or cumulative) stability constants: K-1 = 4.0694 x 10(3) and K-2 = 1.0761 x 10(6), 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 x 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.

Automated summary

This article investigates the formation of metal coordination between a triphenylamine-functionalized salicylaldehyde Schiff base and a copper(II) ion, revealing the dynamic and stable nature of the coordination process. The probe exhibits high sensitivity and specificity towards copper(II) ions, making it a promising fluorescence probe for detection applications.