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

Abstract

The 7Li nuclear resonance correlation spectra of a proposed Li–phenalenyl free radical complex in the interior of the supercages in Li-exchanged Y-type 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 from model), |e 2Qq|/h=1.24±0.04 in units of MHz and |η|=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 1 ″ electron of phenalenyl is partially 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 interaction, implies that there is a substantial additional spin transferred to the 2p orbital of Li in the O–Li bond direction.