EPR spectrum of the Y@C82 metallofullerene isolated in solid argon matrix: hyperfine structure from EPR spectroscopy and relativistic DFT calculations.

The EPR spectrum of the Y@C(82) molecules isolated in solid argon matrix was recorded for the first time at a temperature of 5 K. The isotropic hyperfine coupling constant (hfcc) A(iso) = 0.12 +/- 0.02 mT on the nucleus (89)Y as derived from the EPR spectrum is found in more than two times greater than that obtained in previous EPR measurements in liquid solutions. Comparison of the measured hfcc on a metal atom with that predicted by density-functional theory calculations (PBE/L22) indicate that relativistic method provides good agreement between experiment in solid argon and theory. Analysis of the DFT calculated dipole-dipole hf-interaction tensor and electron spin distribution in the endometallofullerenes with encaged group 3 metal atoms Sc, Y and La has been performed. It shows that spin density on the scandium atom represents the Sc d(yz) orbital lying in the symmetry plane of the C(2v) fullerene isomer and interacting with two carbon atoms located in the para-position on the fullerene hexagon. In contrast, the configuration of electron spin density on the heavier atoms, Y and La, is associated with the hybridized orbital formed by interaction of the metal d(yz) and p(y) electronic orbitals.

Infrared spectroscopic observation of the radical *XeF3 generated in solid argon.

Xenon trifluoride radicals were generated by the solid-state chemical reaction of mobile fluorine atoms with XeF(2) molecules isolated in a solid argon matrix. On the basis of spectroscopic and kinetic FTIR measurements and performed quantum chemical calculations, two infrared absorption bands at 568 (strong) and 523 (very weak) cm(-1) have been assigned to asymmetric and symmetric Xe-F stretching vibrational modes of radical (*)XeF(3), respectively. Chemical reaction of fluorine atom with XeF(2) in a solid argon cage obeys specific kinetic behavior indicating the formation of a long-lived intermediate complex under the condition that the diffusing fluorine atom is attached to isolated XeF(2) at temperatures 20 K < T < 27 K. Subsequent thermally activated conversion in the complex is the main source of novel xenon-containing radical species (*)XeF(3). The rate constant and energy barrier are estimated for the reaction in an argon cage, [XeF(2)-F] --> (K(r)) [XeF(3)], as K(r) approximately 7 x 10(-5) c(-1) at 27 K and E approximately 1.2 kcal/mol, respectively. Quantum chemistry calculations reveal that radical (*)XeF(3) has a planar C(2v) structure. DFT calculations show that formation of the third Xe-F bond in the (*)XeF(3) radical is exothermic, and the binding energy of the third Xe-F bond is 8-20 kcal/mol.