Synthesis of meso-pyridinium porphyrin salts

Self-oriented polycationic copolymers obtained from bipyridinium meso-substituted-octaethylporphyrins

“…It is well known that the free bases and metalated porphyrins with a non electroactive metal undergo two reversible one electron reductions and two reversible one electron oxidations in the potential range of À2 V to 2 V [26]. Previous data have described the reactivity of the p-cation radicals of the metalated [27][28][29][30] and free bases [20] porphyrins. More recent works [20][21][22][23] have established that the substitution of nucleophiles (Nu) on the zinc octaethylporphyrin (Porph.)…”

Electrosynthesis Processes Based on Oxidative Couplings of Porphyrins for the Formation of Supramolecular Assemblies

“…In particular, Smith and coworkers investigated the nucleophilic substitution of nitrite, chloride, pyridine, imidazole, cyanide, triphenylphosphane, thiocyanate, acetate and azide at a meso-position of β-octaalkylporphyrins (see Figure 5). [64][65][66][67] To perform these substitutions, radical cations of the parent unsubstituted porphyrins were always obtained by a chemical oxidation, using oxidants such as iodine, thallium nitrate, triarylammoniumyl salts or N-chlorobenzotriazole. More recently, this chemical oxidative method allowed the grafting of amines and thiols onto a meso-position of porphyrins.…”

“…81 Yet again, the analogous free base [(OEP(py))H 2 ] + porphyrin had previously been obtained by Smith and coworkers using thallium(III) nitrate as chemical oxidant with a much lower yield (45%). 65 Due to the electron-withdrawing effect of the pyridinium substituent onto the macrocycle, 81,85,86 the oxidation waves of the mono-substituted porphyrin (two successive one-electron steps observed at +0.98 and +1.28 V/SCE) are anodically shifted compared to those of the parent unsubstituted (OEP)Zn macrocycle (+0.68 and +0.94 V/SCE, respectively). 86 This explains the fact that only a monosubstitution was permitted when the electrolysis was performed at +0.70 V/SCE, since the potential value was not sufficient to reoxidize the [(OEP(py))Zn] + macrocycle to give the radical cation to allow a second substitution by pyridine.…”

Oxidation of Porphyrins in the Presence of Nucleophiles: From the Synthesis of Multisubstituted Porphyrins to the Electropolymerization of the Macrocycles

“…This is the first example of nucleophilic substitution at the periphery of porphyrin nucleus, allowing afterwards the development of a new and simple convenient synthetic route to obtain varied substituted porphyrins. Indeed, several further works report the nucleophilic attack of nitrogeneous, phosphorous or sulphurous nucleophiles (nitrite ion, pyridine, phosphine, thiocyanate…) onto π-radical cations in meso-position of β-www.intechopen.com octaethylporphyrins or in β-position of meso-tetraphenylporphyrins (Barnett & Smith, 1974;Barnett et al, 1976;Rachlewicz & Latos-Grażyński, 1995;Shine et al, 1979). However, it must be noted that the π-radical cations have been in most cases prepared by chemical ways, principally by oxidation of macrocycles with iodine, bromine or peroxide.…”