Electrophilic reactivities of 7‐L‐4‐nitrobenzofurazans in σ‐complexation processes: Kinetic studies and structure–reactivity relationships

Kinetic and Theoretical Studies of 3,5-Dicyanothiophene Reactivity with Cyclic Secondary Amines in Water and Acetonitrile: Quantification, Correlation, and Prediction

The kinetics of the σ-complexation reactions of 3,5-dicyanothiophene 1 with a series of cyclic secondary amines 2a-c has been studied in water and acetonitrile at 20 °C. Through the linear free energy relationship (LFER) log k = sN (N + E), the electrophilicity parameter E of 3,5-dicyanothiophene 1 has been determined and then integrated into the electrophilicity scale established by Mayr. Molecular dynamics (MD) simulations have been employed to elucidate the reversal in reactivity order between piperidine and pyrrolidine observed in water. Reactivity descriptors like the electronic chemical potential (μ) and the chemical hardness (η) for a series of thiophenes were calculated using the density functional theory (DFT) method. Satisfactory linear correlation (r2 > 0.98) between the experimental electrophilicity parameter (E) of thiophenes 1 and 5a-c and their theoretical global electrophilicity index (ω) has been observed and discussed. In addition, we explore how the E vs. ω relationship can be used to evaluate the electrophilicity parameter E values for other thiophenes that cannot directly measure.

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+.