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|Title:||The effects of catenation on the acidity constants of porphyrin catenanes||Contributor(s):||Gunter, Maxwell John (author); Farquhar, Sandra (author); Jeynes, Tyrone (author)||Publication Date:||2003||Handle Link:||https://hdl.handle.net/1959.11/1590||Abstract:||The acidity constants (pKa₃ and pKa₄) of a series of porphyrins and their corresponding catenanes where the porphyrin is over-arched with a hydroquinol or naphthoquinol polyether strap and mechanically linked to a bipyridinium macrocycle cyclobis-paraquat(4,4'-biphenylene), are calculated from acid-base titration data. As the length of the strap decreases from tetraethylene through triethylene to diethylene, the pKa values decrease, and the separation between pKa₃ and pKa₄ increases. In the diethylene glycol strapped derivatives, only the monocation is accessible above pH = 0. The trend in values reflects the ease of protonation which becomes increasingly difficult as the coulombic repulsions between the protonated porphyrin and the tetracationic macrocycle becomes more severe, as a consequence of enforced proximity of the two charged centres. On protonation, any electronic interactions between the interlinked subunits is replaced by strong electrostatic repulsions. This is alleviated by a 90˚ rotation of the tetracation and a movement away from the porphyrin; such a reorientation is possible only in the longer strapped derivatives, and is prevented in the "tight" analogues.||Publication Type:||Journal Article||Source of Publication:||Journal of Porphyrins and Phthalocyanines, 7(10), p. 667-673||Publisher:||World Scientific Publishing Co Pte Ltd||Place of Publication:||Singapore||ISSN:||1088-4246
|Field of Research (FOR):||030302 Nanochemistry and Supramolecular Chemistry||Peer Reviewed:||Yes||HERDC Category Description:||C1 Refereed Article in a Scholarly Journal||Other Links:||http://www.u-bourgogne.fr/jpp/base_article/index.php?abs=667&n=10&v=07||Statistics to Oct 2018:||Visitors: 46
|Appears in Collections:||Journal Article|
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