Theory of the Spin and Charge Distribution in Aromatic Ion Radicals; Application to the Naphthalene Negative Ion
- 1 November 1961
- journal article
- research article
- Published byĀ AIP PublishingĀ inĀ The Journal of Chemical Physics
- Vol.Ā 35Ā (5), 1873-1883
- https://doi.org/10.1063/1.1732159
Abstract
The valenceābond method is extended to positiveā and negativeāion radicals. General formulas for the required energy, overlap, spinādensity, and chargeādensity matrices are developed and specialized to pielectron systems. An application of the method to the pi electrons of the naphthalene negative ion is given. Included in the calculation are all unexcited structures with the negative charge in each of the ten possible positions. When approximate exchange and transfer integrals are used to determine the coefficients of valenceābond structures, the Ī± to Ī² position spinādensity ratio is found to be equal to 2.60, in good agreement with the ``experimental'' value of 2.65. The magnitudes of the calculated spin densities are such that a Q of ā26.3 gauss is required to obtain the measured hyperfine splittings. To test the validity of these valenceābond results, their sensitivity to the molecular integral values is examined. Also, comparisons with a variety of molecularāorbital calculations are given. It is of considerable interest that the charge distributions obtained from the valenceābond theory and the molecularāorbital theory are very different in spite of the similarity of the spin distributions calculated by the two methods.Keywords
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