Complexation of phenolic guests by endo- and exo-hydrogen-bonded receptors.
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.
Kerckhoffs
Jessica M
JM
Laboratory of Supramolecular Chemistry and Technology, MESA Research Institute, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands.
Ishi-i
Tsutomu
T
Paraschiv
Vasile
V
Timmerman
Peter
P
Crego-Calama
Mercedes
M
Shinkai
Seiji
S
Reinhoudt
David N
DN
D001463:Barbiturates / Q000737:chemistry; D001665:Binding Sites; D047250:Calixarenes; D006860:Hydrogen Bonding; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D010636:Phenols / Q000737:chemistry*; D011955:Receptors, Drug / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014227:Triazines / Q000737:chemistry
D001463:Barbiturates; D010636:Phenols; D011955:Receptors, Drug; D014227:Triazines; C476540:calix(6)arene; D047250:Calixarenes; C011907:melamine