Selective self-organization of guest molecules in self-assembled molecular boxes.
This article describes the synthesis and binding properties of highly selective noncovalent molecular receptors 1(3).(DEB)6 and 3(3).(DEB)6 for different hydroxyl functionalized anthraquinones 2. These receptors are formed by the self-assembly of three calix[4]arene dimelamine derivative molecules (1 or 3) and six diethylbarbiturate (DEB) molecules to give 1(3).(DEB)6 or 3(3).(DEB)6. Encapsulation of 2 occurs in a highly organized manner; that is, a noncovalent hydrogen-bonded trimer of 2 is formed within the hydrogen-bonded receptors 1(3).(DEB)6 and 3(3).(DEB)6. Both receptors 1(3).(DEB)6 and 3(3).(DEB)6 change conformation from staggered to eclipsed upon complexation to afford a better fit for the 2(3) trimer. The receptor selectivity toward different anthraquinone derivatives 2 has been studied using 1H NMR spectroscopy, X-ray crystallography, UV spectroscopy, and isothermal microcalorimetry (ITC). The pi-pi stacking between the electron-deficient center ring of the anthraquinone derivatives 2a-c and 2e-g and the relatively electron-poor melamine units of the receptor is the driving force for the encapsulation of the guest molecules. The selectivity of the hydrogen-bonded host for the anthraquinone derivatives is the result of steric interactions between the guest molecules and the calix[4]arene aromatic rings of the host.
Kerckhoffs
Jessica M C A
JM
Laboratory of Supramolecular Chemistry and Technology, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
ten Cate
Mattijs G J
MG
Mateos-Timoneda
Miguel A
MA
van Leeuwen
Fijs W B
FW
Snellink-Ruël
Bianca
B
Spek
Anthony L
AL
Kooijman
Huub
H
Crego-Calama
Mercedes
M
Reinhoudt
David N
DN
D000880:Anthraquinones / Q000737:chemistry*; D001463:Barbiturates / Q000737:chemistry; D047250:Calixarenes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D010636:Phenols / Q000138:chemical synthesis* / Q000737:chemistry; D014227:Triazines / Q000138:chemical synthesis* / Q000737:chemistry
D000880:Anthraquinones; D001463:Barbiturates; D010636:Phenols; D014227:Triazines; C121325:calix(4)arene; D047250:Calixarenes; C011907:melamine