Binding and Ratiometric Dual Ion Recognition of Zn²⁺ and Cu²⁺ by 1,3,5-Tris-amidoquinoline Conjugate of Calix[6]arene by Spectroscopy and Its Supramolecular Features by Microscopy

Abstract

Lower rim amide linked 8-amino quinoline and 8-amino naphthalene moiety 1,3,5-triderivatives of calix[6]arene L1 and L2 have been synthesized and characterized. While the L1 acts as a receptor molecule, the L2 acts as a control molecule. The complexation between L1 and Cu(2+) or Zn(2+) was delineated by the absorption and electrospray ionization (ESI) MS spectra. The binding ability of these molecules toward biologically important metal ions was studied by fluorescence and absorption spectroscopy. The derivative L1 detects Zn(2+) by bringing ratiometric change in the fluorescence signals at 390 and 490 nm, but in the case of Cu(2+), it is only the fluorescence quenching of 390 nm band that is observed, while no new band is observed at 390 nm. The stoichiometry of both the complexes is 1:1 and was confirmed in both the cases by measuring the ESI mass spectra. The isotopic peak pattern observed in the ESI MS confirmed the presence of Zn(2+) or Cu(2+) present in the corresponding complex formed with L1. Among these two ions, the Cu(2+) exhibits higher sensitivity. The density-functional theory (DFT) studies revealed the conformational changes in the arms and also revealed the coordination features in the case of the metal complexes. The arm conformational changes upon Zn(2+) binding were supported by nuclear Overhauser effect spectrometry (NOESY) studies. The stronger binding of Cu(2+) over that of Zn(2+) observed from the absorption study was further supported by the complexational energies computed from the computational data. While the L1 exhibited spherical particles, upon complexation with Cu(2+), it exhibits chain like morphological features in scanning electron microscopy (SEM) but only small aggregates in the case of Zn(2+). Thus, even the microscopy data can differentiate the complex formed between L1 and Cu(2+) from that formed with Zn(2+).

Unveiling the adsorption mechanism of zeolitic imidazolate framework-8 with high efficiency for removal of copper ions from aqueous solutions

“…43 After Zn 2+ is replaced by Cu 2+ completely, as shown in Scheme1a, the adsorption amount per unit mass of ZIF-8 continuely increases due to the coordination reaction between Cu 2+ and nitrogen atom on 2-methylimidazole, as shown in Scheme 1b. Therefore, the adsorption process of Cu 2+ by ZIF-8 involves ion exchange when the concentration of Cu 2+ is lower than 200 mg L -1 and coordination reaction when the concentration of Cu 2+ is higher than 200 mg L -1 .…”

Investigating the Potential of 8-Amidoquinoline Derivatives as a Fluorescent Probe for Zinc Detection: A Systematic Literature Review

“…They exhibited excellent stability, high affinity to metal ions, and good membrane permeability [48]. However, this zinc (II) chemosensor developed had suffered to differentiate between zinc ion and other competitive cation metals such as Cd 2+ , Cu 2+ , Co 2+ , Ni 2+, and Hg 2+ due to its 3d 10 electronic configurations (spectroscopically silent) [66,70].…”

Dual‐Mode Calixarene‐Based Chemosensor: Highly Selective Fluorogenic Detection of Hg2+ and Chromogenic Detection of Cu2+ with a Single Ionophore

“…Calixarenes, which are macrocyclic compounds containing phenol units linked by a methylene bridge, are found to be very attractive due to their potential application as a host for sensing of various cations as well as anions . Calixarenes can be modified easily at the lower as well as upper rims incorporating appropriate functional groups, which can provide suitable binding sites to the incoming guest ions . We have designed and synthesized a fluorescent molecular sensor incorporating Re I ‐bipyridine moiety as fluorogenic component and amide incorporated calix[4]arene‐azacrown hybrid macrocyclic unit as ion‐recognition moiety.…”