In the EC Literature Electron-Donating or -Withdrawing Nature of Substituents Revealed by the Electrochemistry of Metal-Free Phthalocyanines Efficient Electronic Communication between Two Identical Ferrocene Centers in a Hydrogen-Bonded Dimer Amperometric Assay for Aldose Activity: Antibody- Catalyzed Ferrocenylamine Formation

G.T. Hinckley and P.A. Frey, Anal. Biochem. 349 (2005) 103. One of the most common applications of cyclic voltammetry is to examine the effects of different substituents (e.g., alkyl groups, phosphines, etc.) on the redox potentials of organic molecules and transition-metal-based coordination compounds. The authors of this article used the BASi CV-50W to investigate the electronic effects of a number of functional groups (including alkyl, alkoxy and phenyloxy groups) coordinated at positions R1 R4 of metal-free phthalocyanines.All compounds showed two quasi-reversible one-electron oxidations and up to four quasi-reversible oneelectron reductions. For some derivatives, the first oxidation and first reduction were shifted by the same amount relative to the unsubstituted molecule, so there was no change in the HOMO-LUMO gap. For other derivatives, the first oxidation and first reduction were shifted by different amounts, leading to significant variations in the HOMO-LUMO gap. These variations in the frontier orbitals were similar to those found from the electronic absorption spectra and from molecular orbital calculations.