141
C O M M U N I C A T I O N S T O THE E D I T O R
hyperfine components were so well resolved that even the low abundant l16Sn3+ ions could be detected and Pb3+Complexes i n y-Irradiated Stannous, (Figure 1). Two factors distinguish these centers from those Plumbous, and Plumbic Salts previously described:1$2one is that the magnitudes of Publication costs borne completely by T h e Journal of the hyperfine coupling constants are definitely dePhysical Chemistry pendent upon environment, and the other is the fact that pure salts give good yields of ions that can, forSir: Exposure of tin and lead salts or their aqueous mally, be described as nsl species. solutions t o O0Co y-rays at 77'K gave centers whose The former result, although to be expected, was not esr spectra were characterized by features in the y = found for other ions of this class, even though it was 2 region (-3200 G) together with features in the 5000 G sought. For example, thallous and thallic ions gave region assignable t o the high-field hyperfine components of the doublets from lI7Sn, l19Sn, and 207Pb. T12+ having identical properties.2 The problem is complicated by the fact that several centers show a These are assigned to Sn3+ and Pb3+ centers having marked anisotropy in the high-field components, such Aisoin the region 8550 G (Sn3+)and 12000 G (Pb3+).
Electron Spin Resonance Detection of Sn3+
I
I
I
11 6
VI
Figure 1. High-field hyperfine components in the esr spectrum of ?-irradiated SnS04.
I n the light of our success in preparing and detecting by esr nsl cations such as Cd+, Hg+, and T12+,lJwe have investigated various stannous, plumbous and plumbic salts and their aqueous solutions, and find that in most cases species having the properties expected for Sn3+ and pb3+ ions are formed I). In the particular case of stannous sulfate, the high-field
as that for the magnetic tin isotopes in Figure 1. If this is interpreted as a hyperfine anisotropy, as has been done in Table I, and as one would normally do in such cases, the resulting anisotropy is, apparently, (1) R. 5. Eachus and
(2) M.
M. C. R. Symons, J . Chem. Soc. A , 3080 (1970).
c. R.Symons and J. K. Yandell, ibid., A , 760 (1971). T h e Journal of Physical Chemistry, Vol. 76, No. 1, 1972
COMMUNICATIONS TO THE EDITOR
142 Table I: Esr parameters of Sn3+and Pbsf Field value for highfield linea, G
A value, G
zo7Pb*+
5500 (isotropic)
14,052
2.00
207pb3 f 207Pb 3 +
5348 (isotropic) 5393 (isotropic)
12,400 13,150
2.00 2.006
/I
1
11
1
11ssn3+
5007 5231 4976 5186 4916 5098 4780 (isotropic)
10,480 9,883 8,830 6,251
8,677 8,338 7,722
I . 993
2,029
5255 (isotropic) 5215
10,246 9,733
Material
Pb(NO& in frozen 2.5 M aq HN03 Solid PbCOa Pbe+ doped into CdS
Speoies
I/ Solid SnSOa Solid SnClz Solid SnIa
117Sn3+ l16SnSf Sn8+(separate components not resolved) llQSn3f 117SnS+ ( W n s f not resolved)
far too large for any reasonable admixture of an outer p-orbital, induced, for example, by ligand bonding. We are not yet clear why this should be, and the factors governing the form and magnitude of these large hyperfine couplings are presently being assessed. The latter result is unexpected, as was stressed p r e v i ~ u s l y . ~Thus one might have expected Sna+, for example, to be just a crude representation of an electron in the conduction band or a hole in the valence band, or at least that it would be highly mobile. This
The Journal of Physical Chemistry, Val. 76,No. 1, 2978
1
g
value
2.00 2.00
indicates that there is a considerable modification of the environment around the M3+ units so that a relatively deep trapping center results. Thus these two factors are probably closely linked. (3) R.S. Eachus and M. C . R. Symons, Chem. Commun., 70 (1970).
DEP.4RTMENT
OF
CHEMISTRY
THEUNIVERSITY LEICESTER, LE1 7RH, ENGLAND
R. J. BOOTH H. C . STARICIE M. C . R. SYMONS*
RECEIVED AUGUST6, 1971
