Comparative reactivities of phosphate ester cleavages by metallomicelles

Paolo Scrimin, Giovanna Ghirlanda, Paolo Tecilla, Robert A. Moss

Research output: Contribution to journalReview article

58 Citations (Scopus)

Abstract

The hydrolytic efficiency of the hydrophilic Cu(II) complex of tetramethylethylenediamine (TMED C1· Cu(II)) and the amphiphilic N-n-hexadecyl-N,N′,N′-trimethylethylenediamine complex (TMED C16·Cu-(II)) in comicelles with CTANO3 was studied toward a series of phosphate triesters and diesters that were either neutral (1-7) or cationic and amphiphilic (8-10). While the pseudo-first-order rate constants at [catalyst] = 1 x 10-3 M are larger (ca. one order of magnitude) for the micellar catalyst, the second-order rate constants are higher for the hydrophilic catalyst. With phosphate triesters, regardless of the structure of the substrate, TMED C1·Cu(II)-bound OH- is a better nucleophile than free OH-, while TMED C16· Cu(II)-bound OH- is poorer. This is explained by electrophilic assistance of the metal center which greatly diminishes in micelles. With phosphate diesters the OH- bound to both TMED C1·Cu(II) and TMED C16·Cu(II) is a better nucleophile than free OH-. Partial neutralization of the negative charge of the substrate may explain this behavior. In all cases the amphiphilic substrates are intrinsically more reactive than the neutral ones. Comparison with an iodosobenzoate-based catalyst shows that this is ineffective with phosphate diesters while it is a better reagent than the metallomicellar one with phosphate triesters. Its higher effectiveness, however, seems to vanish as the substrate becomes less reactive.

Original languageEnglish
Pages (from-to)6235-6241
Number of pages7
JournalLangmuir
Volume12
Issue number26
Publication statusPublished - Dec 25 1996

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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    Scrimin, P., Ghirlanda, G., Tecilla, P., & Moss, R. A. (1996). Comparative reactivities of phosphate ester cleavages by metallomicelles. Langmuir, 12(26), 6235-6241.