Synthesis, structural characterization and complexation properties of the first "crowned" dipyrrolylquinoxalines

Gregory J. Kirkovits, Rebecca S. Zimmerman, Michael T. Huggins, Vincent M. Lynch, Jonathan L. Sessler

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

The synthesis of four crown-substituted dipyrrolylquinoxalines 1-4 is reported. The key step in the synthesis is reaction of a 1,2-diaminobenzocrown with 1,2-bis(1H-pyrrol-2-yl)ethanedione (20). A single crystal X-ray diffraction analysis of the 18-crown-6-dipyrrolylquinoxaline 1 revealed that this molecule forms a tetramer centered around a single molecule of water, with no fewer than 10 hydrogen bonds holding the supramolecular structure together. In the case of the 15crown-5-dipyrrolylquinoxaline 2, however, X-ray diffraction analysis revealed that this species exists as a dimeric pair in the solid state, with the NH protons of one pyrrole lying within hydrogen-bonding distance of two oxygen atoms on an adjacent crown ether. A second single crystal structure of 2 was solved; it demonstrated that this system is able to coordinate a potassium cation, thereby forming an intermolecular sandwich complex, at least in the solid state. In [D6]acetone solution receptor 2 and congeners 1, 3 and 4 were also found to complex sodium and potassium cations within the crown diethyl ether binding sites, in a 1:1 manner as judged by 1H NMR spectroscopic analyses. Although systems 1-4 appear to bind fluoride anion as well as cations, the inability to obtain quantitative binding affinities of 1-4 with fluoride anion rendered the evaluation of the systems for cooperative binding impossible.

Original languageEnglish
Pages (from-to)3768-3778
Number of pages11
JournalEuropean Journal of Organic Chemistry
Issue number22
DOIs
StatePublished - Nov 2002
Externally publishedYes

Scopus Subject Areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry

Keywords

  • Crown compounds
  • Host-guest chemistry
  • Hydrogen bonds
  • Supramolecular chemistry

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