Li cation-aromatic organic radical complex in a zeolite studied by electron spin echo envelope modulation spectroscopy

The Li-7 nuclear resonance correlation spectra of a proposed Li-phenalenyl free radical complex in the interior of the supercages in Li-exchanged Y-ty pe faujasite zeolite at 15 K are presented. The spin Hamiltonian parameters , A(xx)/h = 5.23 +/- 0.02, A(yy)/h = 6 +/- 3, A(zz)/h = 167 +/- 9 (signs fr om model), \e(2)Qq\/h = 1.24 +/- 0.04 in units of MHz and \eta\ = 0.0 +/- 0 .2, are shown to be consistent with an sp(n) hybrid orbital on the Li ion, strongly associated with an aluminosilicate bridging O, to which the easily polarizable non-bonding, unpaired, a(n)(1) electron of phenalenyl is parti ally transferred. The isotropic hyperfine interaction, a/h = 59 +/- 2 MHz, implies that 16.3 +/- 0.6% of the spin is transferred to the Li 2s orbital. The anistropic hyperfine interaction, together with the quadrupole interac tion, implies that there is a substantial additional spin transferred to th e 2p orbital of Li in the O-Li bond direction. (C) 2000 Elsevier Science B. V. All rights reserved.