Supramolecular ribbons. Crystal structure and spectroscopic properties of 2, 2′-bipyrroyl

Matthew J. Bernett, Adrianne K. Tipton, Michael T. Huggins, Jonathan H. Reeder, David A. Lightner

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

A crystal structure determination of 2, 2′-bipyrroyl (1; 2, 2′-dipyrryl-diketone, bis (2-pyrrolyl)ethanedione) and its spectroscopic properties in solution are reported. In the crystal, 1 self-assembles via hydrogen bonding into supramolecular ribbons that extend indefinitely through the crystal lattice. The observed molecular conformation is one where each pyrrole ring and adjacent carbonyl group are co-planar (torsion angle ∼0.9°), with the N-H pointing in the same direction as the C=O. The two carbonyls have a transoid but not co-planar geometry with a torsion angle of ∼128°. Adjacent molecules in the crystal are linked by pairs of intermolecular hydrogen bonds, pyrrole NH to carbonyl oxygen, to form a matrix of polymeric chains that lie like neatly stacked, parallel streams of ribbons. Molecular mechanics calculations on the monomer indicate an intra-molecularly hydrogen bonded planar conformation (sp, ap, sp) at the global energy minimum. In CHCl3, 1 is monomeric according to vapor pressure osmometry (MWobs = 179±10 vs · MWcale = 188). In THF, the measured molecular weight is 340±15, which corresponds best to one molecule of 1 solvated by two THF molecules (MW= 322 for C10H8N2O4 · 2 C4H8O) rather than to a dimer.

Original languageEnglish
Pages (from-to)239-249
Number of pages11
JournalMonatshefte fur Chemie
Volume131
Issue number3
DOIs
StatePublished - 2000
Externally publishedYes

Scopus Subject Areas

  • General Chemistry

Keywords

  • Conformational analysis
  • Hydrogen bonding
  • Pyrrole
  • α-Diketone

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