66746-95-0Relevant articles and documents
Electrochemistry and Spectral Characterization of Oxidized and Reduced TPPBrxFeCl Where TPPBrx is the Dianion of β-Brominated-Pyrrole Tetraphenylporphyrin and x Varies from 0 to 8
Tagliatesta, Pietro,Li, Jun,Autret, Marie,Van Caemelbecke, Eric,Villard, Anne,D'Souza, Francis,Kadish, Karl M.
, p. 5570 - 5576 (1996)
The electrochemistry and spectroelectrochemistry of (TPPBrx)FeCl (TPPBrx is the dianion of β-brominated-pyrrole tetraphenylporphyrin and x = 0-8) were examined in PhCN containing tetra-n-butylammonium perchlorate (TBAP) as supporting electrolyte. Each compound undergoes two reversible to quasireversible one-electron oxidations and either three or four reductions within the potential limits of the solvent. The two oxidations occur at the conjugated porphyrin π ring system, and ΔE1/2 between these two lectrode reactions increases as the molecule becomes more distorted. The overall reduction of each compound involves the stepwise electrogeneration of an iron(II), iron(I), and iron(I) π anion radical. An equilibrium between chloride-bound and chloride-free iron(II) forms of the porphyrin is observed with association of the anionic ligand being favored for compounds with x > 5. Singly reduced (TPPBrx)FeCl (x = 0 to x = 6) forms both mono- and bis-CO adducts in CH2Cl2. Only the mono-CO adduct is observed for (TPPBr7)FeCl, and there is no binding at all of CO to (TPPBr7)FeCl. The vco of both the mono- and bis-adducts increases with increase in the number of Br groups, but in a nonlinear fashion which is explained in terms of two competing effects. One is the electron-withdrawing affinity of the Br substitutents and the other the nonplanarity of the macrocycle.
