Electrochemical behavior of the tetracationic porphyrins and

Electrosynthesis and electrochemical properties of porphyrin dimers with pyridinium as bridging spacer

“…This red-shift can be explained by an electron-withdrawing effect of the pyridinium spacer. 22,23 This splitting is accompanied by a broadening of the absorption bands, which suggests also excitonic interactions between the two porphyrin rings. 19 In the case of 4-H 2 -Zn, a broad band around 440-480 nm is observed.…”

“…Many porphyrins bearing pyridinium units as substituents have already been studied in the literature and have shown interesting physical chemistry properties. [20][21][22][23] Nevertheless, to our knowledge, it is the first example of porphyrin dimers with such a spacer. A pyridiniumtype spacer has the advantage of allowing a short distance between the two macrocycles.…”

Porphyrins functionalized by quaternary pyridinium units

“…Replace ment of the counteranion PF 6 by Clleads to formation of porphyrin 12b, without axial pyridine unit coordinated with zinc; the water solubility of 12b showed to be higher than that of 12a [61].…”

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

“…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.…”

“…For instance, electrolyses performed at +0.94, +1.10 and +1.20 V/SCE allowed the formation of the di-, tri-and tetrasubstituted pyridinium (OEP)Zn macrocycles, respectively ([(OEP(py) n )Zn] n+ , n = 2 to 4). [86][87][88] Consequently, a better control of the reactivity is permitted in using the electrochemical method, since it is not possible to choose such a precise value of potential with a chemical oxidant.…”