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

A theoretical and electrochemical impedance spectroscopy study of the adsorption and sensing of selected metal ions by 4-morpholino-7-nitrobenzofuran

The selectivity of a novel chemosensor, based on a modified nitrobenzofurazan referred to as NBD-Morph, has been investigated for the detection of heavy metal cations (Co2+, Pb2+, Mg2+, Ag+, Cu2+, Hg2+, Ni2+, and Zn2+). The ligand, 4-morpholino-7-nitrobenzofurazan (NBD-Morph), was characterized using spectroscopic techniques including FT-IR and 1H NMR. Vibrational frequencies obtained from FT-IR and proton NMR (1H) chemical shifts were accurately predicted employing the density functional theory (DFT) at the B3LYP level of theory. Furthermore, an examination of the structural, electronic, and quantum chemical properties was conducted and discussed. DFT calculations were employed to explore the complex formation ability of the NBD-Morph ligand with Co2+, Pb2+, Mg2+, Ag+, Cu2+, Hg2+, Ni2+, and Zn2+ metal cations. The comparison of adsorption energies for all possible conformations reveals that NBD-Morph exhibits sensitivity and selectivity towards metal ions, including Pb2+, Cu2+, Ag+, and Ni2+. However, an assessment of their reactivity using QTAIM topological parameters demonstrated the ligand's greater complexation ability toward Cu2+ or Ni2+ than those formed by Pb2+ or Ag+. Additionally, molecular electrostatic potential (MEP), Hirshfeld surfaces, and their associated 2D-fingerprint plots were applied to a detailed study of the inter-molecular interactions in NBD-Morph-X (X = Pb2+, Cu2+, Ag+, Ni2+) complexes. The electron localization function (ELF) and the localized-orbital locator (LOL) were generated to investigate the charge transfer and donor-acceptor interactions within the complexes. Electrochemical analysis further corroborates the theoretical findings, supporting the prediction of NBD-Morph's sensory ability towards Ni2+ metal cations. In conclusion, NBD-Morph stands out as a promising sensor for Ni2+.

Synthesis of calixresorcarenes using magnetic poly triazine-benzene sulfonamide-SO3H

The purpose of this work is to develop a magnetically recyclable immobilized base catalyst for the green synthesis of calixresorcarenes. To achieve this, poly triazine-benzene sulfonamide (PTBSA) has been coated on magnetic Fe₃O₄ nanoparticles and subsequently chlorosulfonic acid has been supported to obtain Fe₃O₄@PTBSA-SO₃H. The structure of nano-Fe₃O₄@PTBSA-SO₃H was characterized by TEM, XRD, FT-IR, VSM, WDX, EDX, TGA/DSC and FE-SEM. The catalytic efficiency of this catalyst was also investigated in the synthesis of novel calixresorcarene derivatives. The advantages of heterogeneous nature, catalytic activity and the recyclability of the polymer support were also strengthened by advanced surface treatment. These key factors (basic sites, acidic sites and heterogeneity) play essential roles in the catalyst performance. This procedure has some advantages such as short reaction time, clean and fast work-up and easy separation of the catalyst by an external magnet.

Magnetic poly triazine-benzene sulfonamide-SO₃H was investigated for the synthesis of calixresorcarenes.