Enantiomeric recognition of chiral organic ammonium guests by chiral pyridino-18-crown-6 type ligands in alcohol/dichloroethane solvent mixtures

Xian Xin Zhang, Reed M. Izatt, Jerald S. Bradshaw, P. Huszthy

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Methanol (MeOH), ethanol (EtOH), 2-propanol (iPrOH), and 2-methyI-2-propanol (tBuOH) in binary solvent mixtures of alcohol/1.2-dichloroethane were shown to have a significant effect on enantiomeric recognition of organic ammonium perchlorates by chiral pyridino-18-crown-6 type ligands. Rigid macrocyclic ligands display better recognition in the binary solvents containing small (MeOH and EtOH) than in those containing large (iPrOH and tBuOH) solvent molecules, while a flexible macrocycle (4) shows essentially the same degree of recognition in the four binary solvents. Linear relationships between binding constants of host-guest interactions and reciprocal dielectric constants of the binary solvents are found for the flexible macrocycles, but such relationships do not hold for the rigid crown ethers. Log K, A// and AS values determined by calorimetric titration suggest that the solvent molecules affect the extent of enantiomeric recognition by regulating the conformation of the diastereomeric complexes. The conformations of diastereomeric complexes of the rigid hosts need to be modified in some binary solvents in order to fit the large solvent molecules. This modification results in a decreased degree of enantiomeric recognition. Thus, increased enantiomeric recognition can be obtained by using solvents containing small molecules.

Original languageEnglish
Pages (from-to)64-69
Number of pages6
JournalAnales de Quimica
Volume92
Issue number2
Publication statusPublished - 1996

Fingerprint

Ethylene Dichlorides
Ammonium Compounds
Alcohols
Ligands
Molecules
2-Propanol
Conformations
Crown Ethers
18-crown-6
Titration
Methanol
Permittivity
Ethanol

Keywords

  • Binding constants
  • Chiral crown ethers
  • Enantiomeric recognition
  • Enthalpy
  • Entropy
  • Organic ammonium enantiomers

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Enantiomeric recognition of chiral organic ammonium guests by chiral pyridino-18-crown-6 type ligands in alcohol/dichloroethane solvent mixtures. / Zhang, Xian Xin; Izatt, Reed M.; Bradshaw, Jerald S.; Huszthy, P.

In: Anales de Quimica, Vol. 92, No. 2, 1996, p. 64-69.

Research output: Contribution to journalArticle

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