Title:Ammonium Calixarene Complexes
Volume: 18
Issue: 4
Author(s): Márcio Lazzarotto*
Affiliation:
- Departamento de Qumica Organica, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500-Porto Alegre - Rio Grande do Sul, CEP 91501-970; C.P.: 15003,Brazil
Keywords:
Ammonium cations, calixarenes, host-guest chemistry, inclusion compounds, molecular recognition, supramolecular
chemistry.
Abstract: Calixarenes are macrocyclic compounds that form complexes with ions and neutral molecules.
Association with ammonium cations and calixarenes is directed by coulombic forces, hydrogen
bonding, N+-C-H---π interactions and van der Waals interactions. Calixarenes are stronger acids
than corresponding phenols and react with aliphatic amines by proton-transfer and the ammonium
cations can be placed as exo or endo-calix. The type of aggregate and the association constants are
related to the branching of the chain, the basic character of amine, and the size of the calix. Trimethylammonium
cations, like choline, bind sulfonate calix[4 and 6]arenes and calix[6]arenes by coulombic
and N+-C-H---π interactions. Interaction of calixarenes and ammonium cations has been used
for biological sensors for neurotransmitters and peptide hormones.
