Stepwise effective molarities in porphyrin oligomer complexes: Preorganization results in exceptionally strong chelate cooperativity
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 = 10 2-103 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.
Hogben, Hannah J.,Sprafke, Johannes K.,Hoffmann, Markus,Pawlicki, Milosz,Anderson, Harry L.
p. 20962 - 20969
(2012/03/07)
Probing flexibility in porphyrin-based molecular wires using double electron electron resonance
A series of butadiyne-linked zinc porphyrin oligomers, with one, two, three, and four porphyrin units and lengths of up to 75 A, have been spin-labeled at both ends with stable nitroxide TEMPO radicals. The pulsed EPR technique of double electron electron
Lovett, Janet E.,Hoffmann, Markus,Cnossen, Arjen,Shutter, Alexander T. J.,Hogben, Hannah J.,Warren, John E.,Pascu, Sofia I.,Kay, Christopher W. M.,Timmel, Christiane R.,Anderson, Harry L.
supporting information; experimental part
p. 13852 - 13859
(2010/01/06)
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