Complexation of phenolic guests by endo- and exo-hydrogen-bonded receptors

Org Biomol Chem. 2003 Jul 21;1(14):2596-603. doi: 10.1039/b302836d.

Abstract

This article describes the complexation of phenol derivatives by hydrogen-bonded receptors. These phenol receptors are formed by self-assembly of calix[4]arene dimelamine or tetramelamine derivatives with 5,5-diethylbarbiturate (DEB) or cyanurate derivatives (CYA). The double rosette assemblies 3(3).(DEB)6/(CYA)6 have their phenol-binding functionalities (ureido groups) at the top and at the bottom of the double rosette (exo-receptors). The tetrarosette assemblies 4(3).(DEB)12/(CYA)12 form a cavity with binding sites between the two double rosettes for guest encapsulation (endo-receptors). An intrinsic binding constant Ka of 202 M-1 and 286 M-1 for the binding of 4-nitrophenol to the ureido functionalized exo- and endo-receptors, respectively, was observed. For the exo-receptor a 1:6 stoichiometry was observed while for the endo-receptor 1:4 binding stoichiometry was determined by Job plot and MALDI-TOF MS. The important role that the hydroxy group's acidity plays in the complexation of 4-nitrophenol is clarified by binding studies with different phenol derivatives. The hydrogen-bonded receptors showed a much smaller response towards less acidic phenol derivatives.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Barbiturates / chemistry
  • Binding Sites
  • Calixarenes*
  • Hydrogen Bonding
  • Kinetics
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Conformation
  • Phenols / chemistry*
  • Receptors, Drug / chemistry*
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods
  • Triazines / chemistry

Substances

  • Barbiturates
  • Phenols
  • Receptors, Drug
  • Triazines
  • calix(6)arene
  • Calixarenes
  • melamine