The structure and electronic state of photoexcited fullerene linked with a nitroxide radical based on an analysis of a two-dimensional electron paramagnetic resonance nutation spectrum

Abstract

An electron paramagnetic resonance ͑EPR͒ study of 3,4-fulleropyrrolidine-2-spiro-4Ј-͓2Ј,2Ј,6Ј,6Ј-tetramethyl͔piperidine-1Ј-oxyl ͑1͒ was performed on the photoexcited quartet state in toluene glass. The spectrum of the ͉S,M s͘ϭ͉3/2,Ϯ3/2͘⇔͉3/2,Ϯ1/2͘ transitions was observed selectively by using a two-dimensional ͑2D͒ nutation method and analyzed with a spectral simulation in a randomly oriented system. A position of the nitroxide moiety was determined with respect to the zero-field splitting ͑zfs͒ axes of excited triplet fullerene (3 C 60) by taking into account of the dipolar-dipolar interaction between the radical and 3 C 60 , the hyperfine coupling, the anisotropic g-value of the nitroxide radical, and the zfs of the 3 C 60 moiety. It was found that none of the zfs axes of the 3 C 60 moiety coincide with the local C 2 axis of the molecule which is defined by the position of addition. A symmetry of the electronic structure in 3 C 60 is discussed on the basis of the result.

Excited quartet and doublet states in the complex of tetraphenylporphine zinc (II) and a nitroxide radical in solution: X- and W-band time-resolved EPR studies

“…This might be explained by virtue of broadening effects, but also effects of spin polarization should be taken into account for a quantitative understanding. At any rate, the transition probability for the Q 1 transition is higher by a factor of 4 than that of the D i transition [3,4,8] (see below). Furthermore, the observed g-value of the D 1 state (2.0005) appears to be somewhat larger than that calculated from Eq.…”

“…These Q, and D, states stem from an intramolecular coupling of a stable radical such as nitroxide spin labels and an excited triplet state which is generated by optical excitation of a diamagnetic chromophore such as C60 [1][2][3][4], porphyrin [5][6][7][8], or phthalocyanine [9,10]. There are two interesting situations in these systems; one is an excited spin-multiplet state and the other a radical-triplet pair in photochemical reactions.…”

Direct observation of localized excitation in the lowest excited triplet state of fullerene dimers C120 and C120O by means of time-resolved electron paramagnetic resonance

“…100 ps). As the zfs principal axes of the two units are not parallel each other in the dimer [21], the fast transfer induces an average of D and fast spin relaxations, which is not a case.…”

“…The point charge approximation [19] and spin density distribution of sin 2 h [20] in each unit are utilized for the C 120 structure obtained from X-ray analysis [12]. Here h denotes an angle between the principal z-axis of zfs for the mono-radical-adduct [21] and a radius vector of the particular C atom on the C 120 surface. The calculated D and jEj values are +0.12 and 0.028 GHz.…”

Vector magnetometry based onS=32electronic spins

“…We will present V Si spins in SiC as a model system and also a novel magnetometry scheme using the magic angle. The discussion in this report is also applicable to other S = 3/2 systems which have been found in fullerene [30][31][32][33][34] , organic molecules [35][36][37] , Ni impurities in diamond 38 , and calcium oxide crystals 39 .…”