Schiff base substituted non-peripheral symmetrical cupper, cobalt, and manganese phthalocyanines: Synthesis, design, electrochemistry, and spectroelectrochemistry

Novel Co^II (nANTHCoPc), Cu^II (nANTHCuPc), and Mn^IIICl (nANTH-MnClPc) phthalocyanines were obtained by substituting the 3-(4-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylimino)methyl)phenoxy) Schiff base compound (nANTHOH) obtained by the acid-catalyzed condensation reaction of 4-aminoantipyrine and 4-hydroxybenzaldehyde at non-peripheral positions. By using various spectroscopic techniques, (NMR, MALDI-TOF, FT-IR, and UV–Vis), the structures of green-colored phthalocyanine compounds and precursor phthalonitrile compounds were identified. The electrochemical responses of cobalt (II) (nANTHCoPc), cupper (II) (nANTHCuPc), and manganese (III) (nANTH-MnClPc) phthalocyanines were determined, and their redox responses were analyzed based on the different metal centers. The results indicated that using redox-active Co²⁺ and Mn³⁺ cations instead of Cu²⁺enhanced the redox richness of the complexes due to the observation of extra metal-based electron transfer reactions in addition to the Pc-based ones. In-situ spectroelectrochemical analyses of the complexes were used to support the peak assignments of the redox processes and the spectrum and color of the electrogenerated species during the redox reactions. Supported these redox mechanisms. Multi-electron transfer processes and distinct color changes during these processes indicate the possible usage of these complexes in various electrochemical and opto-electrochemical processes. Metal-based electron transfer reactions illustrated different spectral changes than those of the Pc-based ones, and these spectral changes significantly differed the color of the anionic and cationic species.