A cobalt(II) phthalocyanine with indole substituents: formation, characterization and electrocatalytic studies

• Published in: Journal of coordination chemistry Vol. 72; no. 5-7; pp. 1131 - 1145
• Main Authors: Ngwenya, Vuyelwa, Booysen, Irvin Noel, Mambanda, Allen
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 03.04.2019; Taylor & Francis Ltd
• Subjects: bio-interferents; Charge transfer; Chemical analysis; Cobalt; Cobalt phthalocyanine; Convection; Coordination compounds; Dopamine; electrocatalysis; Electrochemical analysis; Electrochemical impedance spectroscopy; Electrodes; indole; Infrared spectroscopy; Mass spectrometry; Multi wall carbon nanotubes; NMR; Nuclear magnetic resonance; Organic chemistry; Oxidation; Platinum; Rotating disks; Silver chloride
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2019.1599108

Herein, we report the formation of a new cobalt(II) phthalocyanine (CoPc) containing peripheral tetra-substituted indole (CoPc-ind, 2) moieties. The derivatized phthalonitrile, 4-(indole-4-oxy)phthalonitrile (1) as well its corresponding metal complex was characterized by NMR (for 1), IR- and UV-Vis spectroscopy as well as TOF mass spectrometry and elemental analysis (for 2). The electrochemical properties of the N 4 -macrocyclic metal complex were investigated using cyclic- and square-wave voltammetry as well as corroborated by UV-Vis spectroelectrochemistry. The CoPc was electrodeposited onto the surface of a Pt working electrode followed by the immobilization of multiwalled carbon nanotubes (MWCNTs) onto the modified working electrode surface. The electrocatalytic activity of the resultant modified electrode toward dopamine revealed a lower ΔE value of 80 mV versus Ag|AgCl for the modified (2-MWCNTs) Pt electrode compared to the bare Pt electrode (ΔE = 280 mV vs. Ag|AgCl). The diffusion- and convection-controlled electron-transfer kinetics of the chemically modified electrode were evaluated by chronoamperometry and rotating disk electrode techniques. Electrochemical impedance spectroscopic studies revealed that the 2-MWCNTs Pt electrode had a lower charge-transfer resistance and a higher apparent electron-transfer rate constant.