A comparison of the binding of linear chain-linked nitroxides to cyclodextrins and cucurbiturils

Abstract

This study reports the synthesis of six new nitroxides with a paramagnetic moiety attached to a linear alkyl chain, their analyses by electron paramagnetic resonance spectroscopy, and their interaction with two classes of host molecules: cyclodextrins (α- and β-CD) and cucurbiturils (CB[n], n = 6–8). The series of new nitroxides consists of two PROXYL radicals, two TEMPO radicals and two β-phosphorylated nitroxides. As evidenced by changes in the hyperfine coupling constants, the PROXYL and TEMPO spin probes form complexes with CDs by threading of the alkyl chain and/or by inclusion of the paramagnetic moiety. The binding constants of the host–guest complexes, evaluated from the variation in the rotational correlation time with the concentration of the host, fall in the range of 102–103 M−1. The β-phosphorylated nitroxides present low water solubility but are solubilised by interaction with CDs at high concentrations, while complexation with CB[n] has not been evidenced for either probe. The interaction of the cationic nitroxides CAT1 and CAT16 with CDs and CB[n] was also considered in order to elucidate the role played by charged species in the complexation. Both CAT1 and CAT16 form complexes with CB[n]. In the particular case of CAT1/CB[6], the initial association of the complexes at high concentrations of CB[6] was evidenced by the appearance of the spin–spin interaction, followed by oxidation of iodine and separation of red crystals characterized by X-ray diffraction

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BibTeX

@article{joly2026comparison,
  title = {{A comparison of the binding of linear chain-linked nitroxides to cyclodextrins and cucurbiturils}},
  author = {Jean-Patrick Joly and Alexandru-Gabriel Bucur and Iulia Matei and Sevasti Matsia and Muhammed Alkali and Alexandru Vincentiu Florian Neculae and Gerard Audran and Sylvain R A Marque and Anamaria Hanganu and Augustin Madalan and Gabriela Ionita},
  journal = {Organic \& Biomolecular Chemistry},
  year = {2026},
  month = sep,
  doi = {10.1039/d6ob00813e},
  url = {https://hal.science/hal-05743749v1},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - A comparison of the binding of linear chain-linked nitroxides to cyclodextrins and cucurbiturils
AU  - Jean-Patrick Joly
AU  - Alexandru-Gabriel Bucur
AU  - Iulia Matei
AU  - Sevasti Matsia
AU  - Muhammed Alkali
AU  - Alexandru Vincentiu Florian Neculae
AU  - Gerard Audran
AU  - Sylvain R A Marque
AU  - Anamaria Hanganu
AU  - Augustin Madalan
AU  - Gabriela Ionita
PY  - 2026
DA  - 2026/09/09
JO  - Organic & Biomolecular Chemistry
DO  - 10.1039/d6ob00813e
UR  - https://hal.science/hal-05743749v1
AB  - This study reports the synthesis of six new nitroxides with a paramagnetic moiety attached to a linear alkyl chain, their analyses by electron paramagnetic resonance spectroscopy, and their interaction with two classes of host molecules: cyclodextrins (α- and β-CD) and cucurbiturils (CB[n], n = 6–8). The series of new nitroxides consists of two PROXYL radicals, two TEMPO radicals and two β-phosphorylated nitroxides. As evidenced by changes in the hyperfine coupling constants, the PROXYL and TEMPO spin probes form complexes with CDs by threading of the alkyl chain and/or by inclusion of the paramagnetic moiety. The binding constants of the host–guest complexes, evaluated from the variation in the rotational correlation time with the concentration of the host, fall in the range of 102–103 M−1. The β-phosphorylated nitroxides present low water solubility but are solubilised by interaction with CDs at high concentrations, while complexation with CB[n] has not been evidenced for either probe. The interaction of the cationic nitroxides CAT1 and CAT16 with CDs and CB[n] was also considered in order to elucidate the role played by charged species in the complexation. Both CAT1 and CAT16 form complexes with CB[n]. In the particular case of CAT1/CB[6], the initial association of the complexes at high concentrations of CB[6] was evidenced by the appearance of the spin–spin interaction, followed by oxidation of iodine and separation of red crystals characterized by X-ray diffraction
SN  - 1477-0520
SN  - 1477-0539
ER  -

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