A Tetra-Porphyrin Host Exhibiting Interannular Cooperativity

Rhys B. Murphy, Duc Truc Pham, Martin R. Johnston

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    Recently identified as another form of cooperativity, interannular cooperativity is rarely observed in supramolecular chemistry. A tetra-porphyrin molecular tweezer with two bis-porphyrin binding sites is reported that exhibits archetypal interannular cooperativity when complexing 1,4-diazabicyclo[2.2.2]octane (DABCO). The UV/Vis titration data best supported a 1:2 plus 2:2 plus 1:4 complexation model (host:guest), giving K12=6.32×1013 m−2, K22=3.04×1020 m−3, and K14=1.92×1016 m−4 in CHCl3. The NMR titration data supported the formation of two sandwich species, including tetra-porphyrin⋅(DABCO)2 as the major species, although there are speciation differences between UV/Vis and NMR concentrations. Using statistical analysis, interannular cooperativity (γ) for tetra-porphyrin⋅(DABCO)2 was determined to be negative (γ=2.41×10−3), which may be explained by DABCO being too small to be optimally bound simultaneously at both bis-porphyrin binding sites.

    Original languageEnglish
    Pages (from-to)13037-13043
    Number of pages7
    JournalChemistry - A European Journal
    Volume25
    Issue number56
    DOIs
    Publication statusPublished - 8 Oct 2019

    Keywords

    • association constants
    • cooperativity effects
    • porphyrinoids
    • statistical analysis
    • supramolecular chemistry

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