The electron paramagnetic resonance of a number of alternant methylene compounds has been observed, and zero‐field splitting parameters have been obtained. The results are and The interpretation of the data is based upon the observed spin‐density distribution in the alternant free radicals having structures similar to the above triplet molecules. Thus, propargylene, H–↑C↑–C≡C–H, is discussed in terms of a superposition of two π‐electron systems having the same spin‐density distribution as in the allyl radical. Both positive and negative triplet spin densities are required to account for the observed magnitude of D. The lower values of D obtained for the phenyl‐substituted alternant methylenes reflect the delocalization of one of the two triplet electrons into a π orbital of the phenyl group. This effect is more important in the case of phenylpropargylene where a nonzero value of E was obtained. The linear geometry of the alternant methylene chain is responsible for the cases where zero values of E were obtained. The trends in D and trends in linewidths are given qualitative explanations. The discussion assumes that all of the molecules studied have a spectroscopic splitting factor equal to the free‐electron value.
REFERENCES
1.
C. A.
Hutchison
Jr. and B. W.
Mangum
, 34
, 908
(1961
)., J. Chem. Phys.
2.
3.
W.
Yager
, E.
Wasserman
, and R. M. R.
Cramer
, J. Chem. Phys.
37
, 1148
(1962
).4.
R. W.
Murray
, A. M.
Trozzolo
, E.
Wasserman
, and W. A.
Yager
, J. Am. Chem. Soc.
84
, 3213
(1962
).5.
E.
Wasserman
, A. M.
Trozzolo
, W. A.
Yager
, and R. W.
Murray
, J. Chem. Phys.
40
, 2408
(1964
).6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
E. Wasserman, L. Barash, and W. A. Yager (to be published).
16.
E. Wasserman, J. Chem. Phys. (to be published).
17.
R. A. Bernheim (unpublished results).
18.
E.
Wasserman
, L. C.
Snyder
, and W. A.
Yager
, J. Chem. Phys.
41
, 1763
(1964
).19.
R. A.
Bernheim
, R. J.
Kempf
, P. W.
Humer
, and P. S.
Skell
, J. Chem. Phys.
41
, 1156
(1964
).20.
21.
P. S. Skell and J. Klebe, presented at the 137th American Chemical Society Meeting, Cleveland, Ohio, 1960.
22.
P. S. Skell and J. Klebe, presented at the 141st American Chemical Society Meeting, Washington, D.C., 1962.
23.
J. V. Gramas, Ph.D. thesis, The Pennsylvania State University (1965).
24.
This content is only available via PDF.
© 1965 American Institute of Physics.
1965
American Institute of Physics
You do not currently have access to this content.
