Polarization effects in push-pull Buckminsterfullerenes: A semiempirical study
- Universita degli Studi di Bologna (Italy)
We predict that push-pull Buckminsterfullerenes have a high nonlinear optical response that makes pursuing their synthesis worthwhile. Three different semiempirical quantum chemical models concur to show that some isomers of push-pull C{sub 60} have a static first-order hyperpolarizability, {beta}, comparable to or larger than that of all-trans 4-(dimethylamino)-4`-nitrodiphenyloctatetraene. Because of the geometrical structure of push-pull Buckminsterfullerenes, standard models that explain the high response in planar conjugated systems cannot be used. Rather, it is found that conjugation and inductive effects contribute at the same time to {beta} and the separation between the nitrogen-containing groups cannot fully simulate the results of the calculations. A simple perturbation approach based on icosahedral C{sub 60} further confirms the results obtained by the correlations and warrants the search of a topological model able to account for the response. In is found that a linear relation exists between {beta} and the shortest resonant paths between the grafting groups. Two types of resonant structures contribute. They are described in terms of single-double bond alternation. The first resonant structure starts and finishes with hexagon-hexagon alternation (i.e., double bonds) and contributes positively, the second starts and finishes with pentagon-hexagon (i.e., double bonds) and contributes negatively. The ratio of their contributions is roughly two to one. 19 refs., 2 figs., 3 tabs.
- OSTI ID:
- 535461
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 101, Issue 16; Other Information: PBD: 17 Apr 1997
- Country of Publication:
- United States
- Language:
- English
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