Repozytorium
Wyszukaj
Kolekcje
Inne
Stepwise effective molarities in porphyrin oligomer complexes : preorganization results in exceptionally strong chelate cooperativity.
Autorzy
Rok wydania
2011
Czasopismo
Journal of the American Chemical Society
Numer woluminu
133
Strony
20962-20969
DOI
10.1021/ja209254r
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
Complexes of zinc porphyrin oligomers with multivalent ligands can be denatured by adding a large excess of a monodentate ligand, such as quinuclidine. We have used denaturation titrations to determine the stabilities of the complexes of a cyclic zinc–porphyrin hexamer with multidentate ligands with two to six pyridyl coordination sites. The corresponding complexes of linear porphyrin oligomers were also investigated. The results reveal that the stepwise effective molarities (EMs) for the third through sixth intramolecular coordination events with the cyclic hexamer are extremely high (EM = 102–103 M), whereas the values for the linear porphyrin oligomers are modest (EM ≈ 0.05 M). The speciation profiles for the denaturation reactions demonstrate that intermediate species are not significantly populated and that these equilibria are well described by a highly cooperative two-state model.
Adres publiczny
https://doi.org/10.1021/ja209254r