CNDO/2 calcns. showed that for either a Li atom or Li ion intercalated into or between the pyrrole rings, the distance between Li and pyrrole was 0.210-0.216 nm. The intercalated Li formed a polycenter bond with the C atoms. The bond order and bond energy of C:C in pyrrole decreased after intercalation, which was consistent with the disappearance of the IR absorption band at 1560 cm-1. When Li+ was intercalated into a polypyrrole (I) electrode, the LUMO energy of pyrrole changed from pos. to neg. to become an electron acceptor capable of accepting electrons from the Li electrode of the cell. The good conductivity of I was due to the delocalization of p* LUMO and p HOMO of the intercalation compounds over I.

Key words: QUANTUM CHEMISTRY, CNDO APPROXIMATION, CONJUGATED DOUBLE BOND COMPOUNDS, LITHIUM, ELECTROCHEMISTRY, POLYPYRROLE, FRONTIER ORBITAL THEORY, EMBEDDING COLLISIONS