Abstract
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) and γ-cyclodextrin (γ-CD) were investigated by EPR spectroscopy. In the presence of cyclodextrins (i.e., γ-CD, M-β-CD and H-β-CD), host-guest complexes of CT02-VT are formed where the nitroxide and linker parts possibly interact with the cyclodextrins' cavities. Complexation with cyclodextrins leads to suppression of the intramolecular through-space spin-spin exchange coupling in CT02-VT, thus allowing the determination of the through-bond spin-spin exchange coupling which was calculated to be 1.6 G using EPR simulations. Different types of cyclodextrins have different binding affinities with CT02-VT in the order of γ-CD (95 M-1) > M-β-CD (70 M-1) > H-β-CD (32 M-1). In addition, the effect of the linkers in TN biradicals on the host-guest interactions was also investigated. Among the three TN biradicals studied, CT02-VT has the highest association constant with one designated cyclodextrin derivative. On the other hand, the complexes of CT02-GT (∼22 G) and CT02-AT (7.7-9.0 G) with cyclodextrins have much higher through-bond spin-spin exchange couplings than those of CT02-VT (1.6 G) due to the shorter linkers than those of CT02-VT. Furthermore, the stability of TN biradicals towards ascorbate was significantly enhanced after the complexation with CDs, with an almost 2-fold attenuation of the second-order rate constants for all the biradicals. Therefore, the supramolecular host-guest interactions with cyclodextrins will be an alternative method to modulate the magnitude of the spin-spin interactions and redox sensitivity of TN biradicals, and the resulting complexes are promising as highly efficient DNP polarizing agents as well as EPR redox probes.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1694-1701 |
| Number of pages | 8 |
| Journal | Organic and Biomolecular Chemistry |
| Volume | 14 |
| Issue number | 5 |
| DOIs | |
| State | Published - Feb 7 2016 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Biochemistry
Cite this
Supramolecular host-guest interaction of trityl-nitroxide biradicals with cyclodextrins : Modulation of spin-spin interaction and redox sensitivity. / Tan, Xiaoli; Song, Yuguang; Liu, Huiqiang; Zhong, Qinwen; Rockenbauer, Antal; Villamena, Frederick A.; Zweier, Jay L.; Liu, Yangping.
In: Organic and Biomolecular Chemistry, Vol. 14, No. 5, 07.02.2016, p. 1694-1701.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Supramolecular host-guest interaction of trityl-nitroxide biradicals with cyclodextrins
T2 - Modulation of spin-spin interaction and redox sensitivity
AU - Tan, Xiaoli
AU - Song, Yuguang
AU - Liu, Huiqiang
AU - Zhong, Qinwen
AU - Rockenbauer, Antal
AU - Villamena, Frederick A.
AU - Zweier, Jay L.
AU - Liu, Yangping
PY - 2016/2/7
Y1 - 2016/2/7
N2 - 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) and γ-cyclodextrin (γ-CD) were investigated by EPR spectroscopy. In the presence of cyclodextrins (i.e., γ-CD, M-β-CD and H-β-CD), host-guest complexes of CT02-VT are formed where the nitroxide and linker parts possibly interact with the cyclodextrins' cavities. Complexation with cyclodextrins leads to suppression of the intramolecular through-space spin-spin exchange coupling in CT02-VT, thus allowing the determination of the through-bond spin-spin exchange coupling which was calculated to be 1.6 G using EPR simulations. Different types of cyclodextrins have different binding affinities with CT02-VT in the order of γ-CD (95 M-1) > M-β-CD (70 M-1) > H-β-CD (32 M-1). In addition, the effect of the linkers in TN biradicals on the host-guest interactions was also investigated. Among the three TN biradicals studied, CT02-VT has the highest association constant with one designated cyclodextrin derivative. On the other hand, the complexes of CT02-GT (∼22 G) and CT02-AT (7.7-9.0 G) with cyclodextrins have much higher through-bond spin-spin exchange couplings than those of CT02-VT (1.6 G) due to the shorter linkers than those of CT02-VT. Furthermore, the stability of TN biradicals towards ascorbate was significantly enhanced after the complexation with CDs, with an almost 2-fold attenuation of the second-order rate constants for all the biradicals. Therefore, the supramolecular host-guest interactions with cyclodextrins will be an alternative method to modulate the magnitude of the spin-spin interactions and redox sensitivity of TN biradicals, and the resulting complexes are promising as highly efficient DNP polarizing agents as well as EPR redox probes.
AB - 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) and γ-cyclodextrin (γ-CD) were investigated by EPR spectroscopy. In the presence of cyclodextrins (i.e., γ-CD, M-β-CD and H-β-CD), host-guest complexes of CT02-VT are formed where the nitroxide and linker parts possibly interact with the cyclodextrins' cavities. Complexation with cyclodextrins leads to suppression of the intramolecular through-space spin-spin exchange coupling in CT02-VT, thus allowing the determination of the through-bond spin-spin exchange coupling which was calculated to be 1.6 G using EPR simulations. Different types of cyclodextrins have different binding affinities with CT02-VT in the order of γ-CD (95 M-1) > M-β-CD (70 M-1) > H-β-CD (32 M-1). In addition, the effect of the linkers in TN biradicals on the host-guest interactions was also investigated. Among the three TN biradicals studied, CT02-VT has the highest association constant with one designated cyclodextrin derivative. On the other hand, the complexes of CT02-GT (∼22 G) and CT02-AT (7.7-9.0 G) with cyclodextrins have much higher through-bond spin-spin exchange couplings than those of CT02-VT (1.6 G) due to the shorter linkers than those of CT02-VT. Furthermore, the stability of TN biradicals towards ascorbate was significantly enhanced after the complexation with CDs, with an almost 2-fold attenuation of the second-order rate constants for all the biradicals. Therefore, the supramolecular host-guest interactions with cyclodextrins will be an alternative method to modulate the magnitude of the spin-spin interactions and redox sensitivity of TN biradicals, and the resulting complexes are promising as highly efficient DNP polarizing agents as well as EPR redox probes.
UR - http://www.scopus.com/inward/record.url?scp=84956998780&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84956998780&partnerID=8YFLogxK
U2 - 10.1039/c5ob02450a
DO - 10.1039/c5ob02450a
M3 - Article
C2 - 26700002
AN - SCOPUS:84956998780
VL - 14
SP - 1694
EP - 1701
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
SN - 1477-0520
IS - 5
ER -