Electrochemical, Ultrasensitive, and Selective Detection of Nitrite and H2O2: Novel Macrostructured Phthalocyanine with Composite MWCNTs on a Modified GCE.

In the current study, the synthesis of tetra-4-(2-methoxyphenoxy) carboxamide cobalt(II) amide-bridged phthalocyanine (CoTMePhCAPc) is described, as well as its characterization by Fourier transform infrared (FT-IR), UV-visible, and mass spectroscopy; powder X-ray diffraction (PXRD); thermogravimetric analysis (TGA); scanning electron microscopy (SEM); and electrochemistry. Sensing of nitrite (NO2-) and hydrogen peroxide (H2O2) simultaneously was done on CoTMePhCAPc with the composite multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (CoTMePhCAPc/MWCNT/GCE) in the range of linear absorption (NO2- and H2O2: CV 50-750, differential pulse voltammetry (DPV) 50-750, CA 50-500 nmol L-1), lower detection limit (NO2- and H2O2: CV 10.5 and 12.5, DPV 10.5 and 11.2, CA 6.0 and 5.5 nmol L-1), and sensitivity (NO2- and H2O2: CV 0.379 and 0.529, DPV 0.043 and 0.049, CA 0.033 and 0.040 µA nM-1 cm-2). The composite electrode exhibits improved electrocatalytic behavior compared to modified electrodes for nitrite and H2O2. The CoTMePhCAPc/MWCNT/GCE sensor displays good selectivity even in the presence of an excess of interfering metal ions and biomolecules at the applied potentials of +400 mV (nitrite) and -400 mV (H2O2). Moreover, the fabricated sensor was studied with various phosphate-buffered saline (PBS) (pH 5-9) electrolyte solutions. The unknown H2O2 concentration in blood samples and apple juice and nitrite concentration in drinking water and butter leaf lettuce were all measured using the usual addition method. Docking analysis clearly indicates that the ligand shows excellent inhibition activity toward the three subjected protein molecules.

Pi-donor/acceptor effect on Lindqvist type polyoxomolibdates because of various multiple-bonded nitrogenous ligands.

The electronic structures of Lindqvist type functionalized polyoxometalates (POM) ([Mo6O18R]n- R=O, NO, NAr, NNAr, NNAr2; n=2, 3) have been investigated using density functional methods. We discuss the role of the replacement of terminal oxo ligands by pi-donor/acceptor multiple-bonded nitrogenous ligands on the basis of geometrical parameters, charge analyses, reactivity indexes, and vibrational spectra. The calculated reactivity indexes (chemical potential, electronegativity, hardness, and electrophilicity) indicate that the most reactive functionalized POMs are those substituted by pi-acceptor ligands. These pi-acceptor ligands induce a decrease in the hardness and an increase in the chemical potential and electrophilicity, thus increasing the reactivity. Our calculations are in reasonable agreement with reported experimental data.