Ethyne-porphyrin

Vitamin B12 catalyzed also the dechlorination of tetrachloroethene (PCE) to tri-chloroethene (TCE) and 1,2-dichloroethene (DCE) in the presence of dithiothreitol or Ti(III) citrate [137-141], but zero-valent metals have also been used as bulk electron donors [142, 143]. With vitamin B12, carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction cis-l,2-DCE, ethene, and ethyne were the main products [138, 139]. Using Ni(II) humic acid complexes, TCE reduction was more rapid, leading to ethane and ethene as the primary products [144, 145]. Angst, Schwarzenbach and colleagues [140, 141] have shown that the corrinoid-catalyzed dechlorinations of the DCE isomers and vinyl chloride (VC) to ethene and ethyne were pH-dependent, and showed the reactivity order 1,1-DCE>VC> trans-DCE>cis-DCE. Similar results have been obtained by Lesage and colleagues [146]. Dror and Schlautmann [147, 148] have demonstrated the importance of specific core metals and their solubility for the reactivity of a porphyrin complex. 

Scheme 1-14 Inside the porphyrin trimer 39 cavity, diene 52 and dienophile 53 react selectively to give the exo adduct 54. The smaller version of trimer 39, with two butadiyne links replaced with ethyne units, templates the reaction with the opposite stereochemistry, to give the endo isomer of 54.

An interesting modification of the monomer giving rise to 40 was carried out by Aida et al. by inserting the ethyne-l,2-diyl bridge between the porphyrin rings [104]. The monomer so modified self-assembles in CHCI3... 

Ostrowski, J.C., K. Susumu, M.R. Robinson, M.J. Therien, and G.C. Bazan (2003). Near-infrared electroluminescent light-emitting devices based on ethyne-bridged porphyrin fluorophores. Arfv. Mater. 15(15), 1296-1300. 

Scheme 45 Stnictural formulas of push-pull Zn porphyrins with polycyclic aromatic D composed of ethyne-linked moieties and the AN4 co-adsoibent used in Refs. [87, 88]...

Fletcher JT, Therien MJ (2000) Transition-meteil-mediated [2 + 2+2] cycloaddition reactions with ethyne-containing porphyrin templates new routes to cofacial porphyrin structures and faciaUy-functionalized (porphinato)metal species. J Am Chem Soc 122(49) 12393-12394... 

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