Supramolecular host–guest interaction of trityl-nitroxide biradicals with cyclodextrins: modulation of spin–spin interaction and redox sensitivity

• DOI: 10.1039/c5ob02450a
• Publication Date: 2015-12-18T10:32:09Z
• Authors: Xiaoli Tan; Yuguang Song; Huiqiang Liu; Qinwen Zhong; Antal Rockenbauer; Frederick A. Vill...; Jay L. Zweier; Yangping Liu
• Keywords: Modulation (music)

Supramolecular host-guest interactions of trityl-nitroxide (TN) biradicals CT02-VT, CT02-AT and CT02-GT with methyl-β-cyclodextrin (M-β-CD), hydroxypropyl-β-cyclodextrin (H-β-CD) γ-cyclodextrin (γ-CD) were investigated by EPR spectroscopy. In the presence cyclodextrins (i.e., γ-CD, M-β-CD H-β-CD), complexes CT02-VT are formed where nitroxide linker parts possibly interact cyclodextrins' cavities. Complexation leads to suppression intramolecular through-space spin-spin exchange coupling in thus allowing determination through-bond which was calculated be 1.6 G using simulations. Different types have different binding affinities order γ-CD (95 M(-1)) > (70 H-β-CD (32 M(-1)). addition, effect linkers TN on also investigated. Among three studied, has highest association constant one designated cyclodextrin derivative. On other hand, (∼ 22 G) (7.7-9.0 much higher couplings than those (1.6 due shorter CT02-VT. Furthermore, stability towards ascorbate significantly enhanced after complexation CDs, an almost 2-fold attenuation second-order rate constants for all biradicals. Therefore, supramolecular will alternative method modulate magnitude redox sensitivity biradicals, resulting promising as highly efficient DNP polarizing agents well probes.