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 low 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 interpretation of the data, the hyperfine coupling constants for the muon and proton of the - CHMu methylene group in two different orientations for the radical bound to the S-II cation site have been determined. At 322 K these values 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 results 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 interaction of the pi electron density with the Na cation. (C) 2000 Elsevier Science B.V. All rights reserved.