Azo-methoxy-calix[4]arene complexes with metal cations for chemical sensor applications: Characterization, QTAIM analyses and dispersion-corrected DFT- computations

In this work, the structures, quantum chemical descriptors, morphologic characterization of the azo-methoxy-calix[4]arene were investigated. The analyses and interpretation of the theoretical and the experimental IR spectroscopy results for the corresponding compounds was performed. The complexation of the azo-methoxy-calix[4]arene with Zn2+,Hg2+ , Cu2+ , Co2+, Ni2+ , Pb2+ and Cd2+metal cations has been calculated by the dispersion corrected density functional theory (DFT-D3). The values of the interaction energies show that the specific molecule is more selective to the Cu2+ cation. The study of the reactivity parameters confirms that the azo-methoxy-calix[4]arene molecule is more reactive and sensitive to the Cu2+ cation than that Co2+ and Cd2+. In addition, the investigation of the electrophilic and nucleophilic sites has been studied by the molecular electrostatic potential (MEP) analysis. The Hirshfeld surface (HS) analysis of the azo-methoxy-calix[4]arene-Cu2+ interaction have been used to understand the Cu⋯hydrogen-bond donors formed between the cation and the specific compound. The Quantum Theory of Atoms in Molecules (QTAIM) via Non covalent Interaction (NCI) analysis was carried out to demonstrate the nature, the type and the strength of the interaction formed between the Cu2+ cation and the two symmetrical ligands and the cavity. Finally, the chemical sensor properties based on the Si/SiO2/Si3N4/Azo-methoxy-calix[4]arene for detection of Cu2+ cation were studied. Sensing performances are determined with a linear range from 10-5.2 to 10-2.2 M. The Si/SiO2/Si3N4/azo-methoxy-calix[4]arene structure is a promoter to have a good performance sensor.