TR-EPR of single and double spin labelled C<sub>60</sub>derivatives: observation of quartet and quintet excited states in solution

Franco, Lorenzo; Mazzoni, Martina; Corvaja, Carlo; Gubskaya, V. P.; Berezhnaya, L. Sh.; Нуретдинов, И. А.

doi:10.1080/00268970600577614

Cited by 27 publications

(28 citation statements)

References 19 publications

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“…A peculiar time dependence, which can only be demonstrated at higher frequencies, is observed. The results are compared with those on related systems and in particular with the earlier X-band TREPR measurements at room 40 and low temperature. 41…”

Section: Introductionmentioning

confidence: 93%

“…20 In the mid-90's, the groups of Corvaja 21 and Yamauchi 22 simultaneously demonstrated the intramolecular radical-triplet pair interaction in molecular systems composed of a chromophore and a radical linked by covalent and coordinative bonds, respectively. These results opened a new field of research in intramolecular spin interactions and dynamics in spin-labeled molecular structures such as porphyrins and phthalocyanines, [23][24][25][26][27] peptides, [28][29][30] fullerene derivatives, [31][32][33][34][35][36][37][38][39][40][41] purely organic p-conjugated systems [42][43][44] and metal-based porphyrin systems. [45][46][47][48][49][50][51][52] Many such systems have since been studied by TREPR (Transient Electron Paramagnetic Resonance).…”

Section: Introductionmentioning

confidence: 99%

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W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives

Moons

Goovaerts

Gubskaya

et al. 2011

Phys. Chem. Chem. Phys.

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We investigated by W-band (94 GHz) transient electron paramagnetic resonance (TREPR) and photoinduced absorption (PIA) spectroscopy two fullerene derivatives bearing a nitroxide radical unit. After pulsed laser photoexcitation of the molecules in liquid toluene solution, complex EPR spectra are recorded, with lines in absorption and emission. The intrinsic higher spectral and temporal resolution of the W-band frequency leads to the assignment of all the lines in the spectrum and the determination of the sign and the absolute value of the exchange coupling between the fullerene in its photoexcited triplet state (S(T) = 1) and the radical (S(R) = 1/2). The two compounds with different fullerene-nitroxide spacers show opposite-ferromagnetic and antiferromagnetic-exchange couplings. The time evolution of the spectra and the polarization of the lines are interpreted in terms of several possible spin polarization mechanisms. The EPR measurements are complemented with PIA experiments.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives

Moons

Goovaerts

Gubskaya

et al. 2011

Phys. Chem. Chem. Phys.

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“…We have previously shown that pulsed photoexcitation of a new fullerene-linked bis-nitroxide gave a compound with a wellresolved transient EPR spectrum, assigned to an excited quintet spin state generated by spin-coupling of the nitroxides and the fullerene excited triplet. 19,20 The synthesis, structure and biological activity of nitroxide methanofullerenes 2 and 4 has not been a previously described. In this paper, the synthesis, structure and biological activities of methanofullerenes containing one or two nitroxide fragments are reported.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, structure and biological activity of nitroxide malonate methanofullerenes

et al. 2007

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study has also revealed some flaws in the previous model of inter-double-helix hydrogen bonding. [1] Imberty, A.; Chanzy, H.; Pérez, S.; Buléon, A.; Tran, V. Functionally substituted fullerene derivatives are of interest since it is possible to obtain both biologically active substances and new materials for nanotechnology on their basis. The spherical platform of fullerene allows one to design molecules with various fragments, which are responsible for the specific properties. At the same time the crystal structure of such compounds is studied insufficiently, that is why Crystallographic Data Bases contain information about not more than 80 fullerene C60 derivatives structures. Interesting feature of these compounds (both derivatives and fullerene complexes) in solid state is their active participation in pi-electronic interactions between each other and with other compounds incorporating aromatic fragments. Owing to these interactions the compounds can form in a crystal the supramolecular structures of various type, that, apparently, finds reflection in their particular properties. Basing on literature structural data for organic derivative of fullerene and on our original X-ray data for the bis-and mono-adducts of the methanofullerenes and pyrrolidino-fullerenes, we have analysed the intermolecular interactions, crystal packing and supramolecular structure of these compounds from the point of view of such interactions. It was found, that in spite of the presence of large substituents in the molecules and solvate molecules in the crystals, which hinder such interactions, the fullerene fragments are closely packed with different fullerene environments-honeycomb structure, zigzag-chain,  dimers, columns and layers, and preferably interact face-to-face with the 5-and 6-membered aromatic rings. The majority of the compounds forms 2D-structures-layers of various topology with fullerenes coordination equal to 3 or 4. Presence of molecules-guests with aromatic fragments or aromatic fragments in the fullerene derivatives leads to their obligatory participation in such interactions and to the destruction of the fullerene-fullerene interactions. Recently we carried out the synthesis of malonate nitroxide metanofullerene, which shows, in combination with known anticancer drug cyclophosphamide, the high antitumor activity against leukemia P-388. It was shown by X-ray single crystal analysis that methanofullerene with two nitroxide groups has a diamond-like environment in the crystal due to fullerene-fullerene interactions [1]. In the same time the first examples of the phosphorylated mono-and bis-methano-fullerenes with large substituents have lower coordination of fragments-zigzag chains and pi-dimers. The comparative analysis of the results for the organic derivatives and for the fullerene C60 inclusion compounds is presented. The topology of the crystals is analysed additionally on the base of proposed model of localization of hydrophilic and hydrophobic regions in the crystals of organic compounds. Keywords: hydrogen...

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“…3. As it was observed for liquid solutions [13], also the frozen matrix TR-EPR spectra of Ia and Ib are different. The spectrum of Ia is characterized by a strong absorption in the center of an absorption/emission (A/E) pattern.…”

Section: Resultsmentioning

confidence: 86%

TR-EPR of single and double spin-labeled C60 derivatives in frozen matrices

et al. 2006

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Abstraet. Time-resolved electron paramagnetic resonance spectra of two single spin-labeled and two double spin-labeled C6o derivatives in frozen solution are recorded with pulsed laser excitation and 100 ns time resolution. Quartet and quintet excited species are detected which arise from the electron spin coupling of the triplet excited fullerene moiety with the unpaired spin(s) of the nitroxide label(s). Despite the similar molecular structure, in both series of single and double labeled derivatives a different behavior was found, which is due to substantial difference of the energy of exchange coupling.

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TR-EPR of single and double spin labelled C₆₀derivatives: observation of quartet and quintet excited states in solution

Cited by 27 publications

References 19 publications

W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives

W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives

Synthesis, structure and biological activity of nitroxide malonate methanofullerenes

TR-EPR of single and double spin-labeled C60 derivatives in frozen matrices

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TR-EPR of single and double spin labelled C60derivatives: observation of quartet and quintet excited states in solution

Cited by 27 publications

References 19 publications

W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives

W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives

Synthesis, structure and biological activity of nitroxide malonate methanofullerenes

TR-EPR of single and double spin-labeled C60 derivatives in frozen matrices

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TR-EPR of single and double spin labelled C₆₀derivatives: observation of quartet and quintet excited states in solution