Spectroscopic characterization, host-guest charge transfer, Hirshfeld surfaces, AIM-RDG and ELF study of adsorption and chemical sensing of heavy metals with new derivative of Calix [4]quinone: A DFT-D3 computation

Abstract

Attributing to the chemical sensor application based on charge transfer phenomena between the host and the guest for new derivative of calix [4]quinone, 1,3-alternate-calix [4]quinone (C4Q), have been investigated via DFT-D3 calculation and compared to the experimental data. The structural design of the title molecule has been characterized, and the organic quinone has been clearly identified. The selected sites for the Cu2+, Ag2+ and Hg2+ cations by the calix [4]quinone molecule have been discussed. The molecular electrostatic potential (MEP) map has been performed in order to identify the highly attractive site for the selected cations. The 1H NMR chemical shifts of the stable complexes have been calculated. Moreover, the calculated stretching vibrational modes in the most stable conformations have been assigned and compared with the experimental ones. The UV–Vis spectroscopy revealed that the interaction of the Cu2+, Ag2+ (d9 electron configuration) and Hg2+(d10 electron configuration) cations with the C4Q is reinforced with the red shifting to high absorption bands of the free molecule. The HOMO and LUMO orbital iso-surfaces exhibit that the C4Q-Cu2+ complex has the highest charge transfer terms (CTT) which increased the overall energetic stabilization of the system. The Hirshfeld surface (HS) showed the highly attractive energetic binds that favor the efficient charge transfer phenomena between the two systems. The interactions between the host (C4Q) and guest (metal cation) are discussed deeply using the topological AIM and non-covalent RDG index analyses. The computed values from electron density and the binding energies for all active bonds have been interpreted. Finally, the ELF/LOL at bond critical points and ELF maps are computed to confirm and visualize the donor-acceptor couple formed between the selected host-guest systems.