Ethynylphenyl-Derivatized Free Base Porphyrins: Anodic Oxidation Processes and Covalent Grafting onto Glassy Carbon Electrodes
Citation:
Gamm, P.; Sheridan, M. V.; Van Wyck, S. J.; Meindl, A.; Senge, M. O.; Geiger, W. E., Ethynylphenyl-Derivatized Free Base Porphyrins: Anodic OxidationProcesses and Covalent Grafting onto Glassy Carbon Electrodes, Langmuir, 2020, 36, 96–108Download Item:
Abstract:
In six of seven cases, direct anodic oxidation of the ethynyl group of an ethynylphenyl-derivatized free-base porphyrin gave modified glassy carbon electrodes in which the porphyrin was strongly surface-bound, most likely in a perpendicular geometry through covalent attachment of the ethynyl group to a surface carbon atom. The porphyrins each contained an ethynylphenyl group in one meso position and varied in the groups present in the other three meso positions. Electrografted 5,10,15,20-tetrakis(ethynylphenyl)porphyrin, H21, which has ethynyl moieties in all four meso positions, has well-defined surface voltammetry and grows to multilayer levels upon repeated cyclic voltammetry (CV) deposition scans. Multilayering was not observed to the same degree for monoethynylphenyl-substituted porphyrins and became progressively less for porphyrins having groups in the 15-meso position that were more protective against ethynyl radical attack. Clean molecular monolayer-level coverage was observed for 5-ethynylphenyl-10,20-bis(3-methoxyphenyl)-15-hexylporphyrin, H25. Owing to the fact that the ethynyl oxidation potential (1.1 to 1.5 V vs ferrocene) is more positive than that of the second macrocycle oxidation, the longevities and follow-up reactions of the porphyrin dications were also studied by CV, chemical oxidation, and optical spectroscopy in homogeneous solution. The primary follow-up products of the doubly oxidized porphyrins, whether surface-bound or in solution, were pyrrole-protonated species that were easily reduced back to the neutral porphyrin.
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Grant Number
Science Foundation Ireland
IvP 13/IA/1894
Author's Homepage:
http://people.tcd.ie/sengem
Author: Senge, Mathias
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Journal ArticleCollections
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Langmuir;Availability:
Full text availableKeywords:
Redox reactions, Reaction mechanisms, Pyrroles, Electrodes, OxidationDOI:
http://dx.doi.org/10.1021/acs.langmuir.9b03452Metadata
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