Anion-driven conformational polymorphism in homochiral helical coordination polymers

J Am Chem Soc. 2009 Aug 5;131(30):10452-60. doi: 10.1021/ja901154p.

Abstract

Three homochiral 3D frameworks are assembled based on periodically ordered arrays of helices built from axial chiral 3,3'-bipyridine-5,5',6,6'-tetramethyl-2,2'-dimethoxy-1,1'-biphenyl ligands and linearly coordinated Ag(I) ions. The aggregation behavior of silver salts and the ditopic ligand in solutions was investigated by a variety of techniques, including (1)H NMR, UV-vis, CD, GPC and MALDI-TOF. The cationic polymer skeleton exhibits an unprecedented conformational polymorphism in the solid-state, folding into two-, three- and four-fold helices with NO(3)(-), PF(6)(-) and ClO(4)(-) as the counteranion, respectively. The two-fold helices cross-link via argentophilic Ag-Ag interactions to form sextuple helices, which lead to a three-dimensional (3D) chiral framework. The three-fold or four-fold helices, on the other hand, self-associates in pairs to form three-dimensional tubular architectures. This anion-dependent self-assembly behavior can be rationalized by considering the sizes, geometries and binding abilities of the counteranions and subsequent chain conformation to minimize steric repulsions and maximize secondary interactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anions / chemistry*
  • Biphenyl Compounds / chemistry
  • Chromatography, Gel
  • Crystallography, X-Ray
  • Ligands
  • Models, Molecular
  • Molecular Conformation*
  • Organometallic Compounds / chemistry*
  • Polymers / chemistry*
  • Silver / chemistry
  • Spectrum Analysis
  • Stereoisomerism
  • Substrate Specificity

Substances

  • Anions
  • Biphenyl Compounds
  • Ligands
  • Organometallic Compounds
  • Polymers
  • diphenyl
  • Silver