Electrochemistry of Porphyrinoids and Tetrapyrrole Triple-Decker Complexes

This dissertation describes the electrochemistry and spectroelectrochemistry of porphyrinoids and tetrapyrrole triple-decker complexes, which were examined in nonaqueous media using electrochemical techniques in combination with spectroelectrochemical analysis as a function of the central metal ions, the axial ligands, the π-conjugated macrocycles, the peripheral substituents as well as solution conditions. Examined macrocyclic compounds in this dissertation are (i) meso-nitrophenyl metalloporphyrins; (ii) meso-diphosphorylated metalloporphyrins; (iii) unsymmetrical mono-benzoporphyrins; (iv) push-pull opp-dibenzoporphyrins; (v) phthalocyanine-corrole and phthalocyanine-porphyrin triple-decker complexes. In addition to two ring-centered reductions and two ring-centered oxidations, the meso-nitrophenyl metalloporphyrins exhibit reductions of the electroactive NO2Ph groups with a first reversible one-electron-addition followed by one or more irreversible reductions at more negative potentials. The meso-diphosphrylated porphyrins exhibit a slow chemical reaction after the second ring-centered reduction, forming a redox-active phlorin anion which can either be re-oxidized back to the initial porphyrin or be further reduced to form the phlorin dianion. The β, β’-fused mono-benzoporphyrin and opp-dibenzoporphyrin possess smaller HOMO-LUMO gaps and red-shifted and broadened absorption bands compared to those of the corresponding non-benzo porphyrin derivatives, due to the extension of the π-system. The Pc-M-Cor-M-Pc triple-decker complexes bearing nitrophenyl groups on the corrole unit exhibit 5 oxidations and 3-5 reductions depending on the number of the redox-active NO2Ph groups. However, the Pc-M-Pc-M-Por triple-deckers exhibit 4 oxidations and 3 reductions with the first oxidation and the first reduction both being assigned as a one-electron-transfer process on the Pc macrocycle.