Model calculations of the interaction of two parallel antiaromatic 4n pi-electron systems.

The nature of the interaction between decks of a pentalene dimer and an s-indacene dimer has been studied by semi-empirical MNDO/1 and MINDO/3 calculations for distances between decks of from 5 A to 2 A. In contradiction to qualitative predictions from a frontier orbital analysis, it is found that the 4n-4n pi-electron interaction between decks for such dimers is destabilizing for distances exceeding about 2.5 A.