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|Title:||Binding and Ratiometric Dual Ion Recognition of Zn2+ and Cu2+ by 1,3,5-Tris-amidoquinoline Conjugate of Calixarene by Spectroscopy and Its Supramolecular Features by Microscopy|
|Keywords:||Selective Fluorescent Sensor|
|Publisher:||AMER CHEMICAL SOC|
|Citation:||ANALYTICAL CHEMISTRY, 87(9)4988-4995|
|Abstract:||Lower rim amide linked 8-amino quinoline and 8-amino naphthalene moiety 1,3,5-triderivatives of calixarene L-1 and L-2 have been synthesized and characterized. While the L-1 acts as a receptor molecule, the L-2 acts as a control molecule. The complexation between L-1 and Cu2+ or Zn2+ 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 L-1 detects Zn2+ by bringing ratiometric change in the fluorescence signals at 390 and 490 nm, but in the case of Cu2+, 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 Zn2+ or Cu2+ present in the corresponding complex formed with L-1. Among these two ions, the Cu2+ 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 Zn2+ binding were supported by nuclear Overhauser effect spectrometry (NOESY) studies. The stronger binding of Cu2+ over that of Zn2+ observed from the absorption study was further supported by the complexational energies computed from the computational data. While the L-1 exhibited spherical particles, upon complexation with Cu2+, it exhibits chain like morphological features in scanning electron microscopy (SEM) but only small aggregates in the case of Zn2+. Thus, even the microscopy data can differentiate the complex formed between L-1 and Cu2+ from that formed with Zn2+.|
|Appears in Collections:||Article|
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