Hfcs of the C(6)H(6)Mu radical in NaY zeolites

The hyperfine interactions of the MuC(6)H(6), radical in NaY zeolites at lo w to moderate benzene loadings have been measured by both the FT-mu SR and ALC-mu SR techniques over a wide temperature range. From a preliminary inte rpretation of the data, the hyperfine coupling constants for the muon and p roton of the - CHMu methylene group in two different orientations for the r adical bound to the S-II cation site have been determined. At 322 K these v alues are: A(mu)(1)= 606 +/- 2 MNz and A(p)(1)= 108 +/- 2 MHz, for the muon on the opposite side of the ring from the cation; and A(mu)(2) = 430 +/- 2 MHz and A(p)(2) = 70 +/- 5 MHz, for the muon on the same side. These resul ts as well as their trends with temperature demonstrate that the MuC(6)H(6) radical adopts a non-planar equilibrium geometry due to the strong interac tion of the pi electron density with the Na cation. (C) 2000 Elsevier Scien ce B.V. All rights reserved.