Inclusion complexes of cyclodextrins with biradicals linked by a polyether chain--an EPR study.
Complexation of beta-cyclodextrin with flexible nitroxide biradicals linked by a polyethylene glycol chain was monitored by EPR spectroscopy. The EPR spectra of the uncomplexed biradicals show an exchange interaction due to the flexibility of the polyethylene glycol chain. Complexation with cyclodextrin leads to the disappearance of the exchange interaction in the EPR spectra. The complexation can be reversed by the addition of competing guests (e.g., adamantane derivatives). At high concentration, the inclusion complexes precipitate, and differential scanning calorimetry (DSC) of the precipitates proved the formation of complexes. Elemental analysis data revealed that the complexes contain several cyclodextrin units per biradical but that the composition was not stoichiometric.
Ionita
Gabriela
G
Laboratory of Quantum Chemistry and Molecular Structure, Institute of Physical Chemistry Ilie Murgulescu, Bucharest, Romania. gabi2ionita@yahoo.com
Meltzer
Viorica
V
Pincu
Elena
E
Chechik
Victor
V
D003497:Cyclic N-Oxides / Q000737:chemistry; D003505:Cyclodextrins / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D004987:Ethers / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D013113:Spin Labels
D003497:Cyclic N-Oxides; D003505:Cyclodextrins; D004987:Ethers; D005609:Free Radicals; D009589:Nitrogen Oxides; D013113:Spin Labels; D011092:Polyethylene Glycols; C039900:nitroxyl; C003959:TEMPO