MNDO STUDY OF CHARGED COMPLEXES OF DODECAHEDRON-SHAPED C(20) WITH LI

Singly charged complexes of dodecadedron-shaped C, with Li were studie d by means of the MNDO semiempirical method and optimal structures, en ergies and harmonic vibrations were obtained for C20, C20(2-), [C20.Li ]+ and [C20.Li]-. Two locations of the Li atom were treated (external and internal) and the external complexes were found to be thermodynami cally more stable by at least 600 kJ mol-1. The internal location is, however, kinetically stabilized by a potential barrier of about 1000 k J mol-1. The interactions with the Li atom do not produce substantial changes in the cage geometry, but they can be well seen in the vibrati onal patterns.