DECOMPOSITION ANALYSES OF THE INTERMOLECULAR INTERACTION ENERGIES IN 2 PI-PI STACKING COMPLEXES - QUINHYDRONE AND N,N,N',N'-TETRAMETHYL-P-DIAMINOBENZENE-CHLORANIL COMPLEX

Although there is a similarity in the orbital interaction scheme betwe en quinhydrone and N, N,N',N' -tetramethyl-p-diaminobenzene-chloranil complex, the stacking conformations are different from each other. The former prefers the half-stacked conformation, whereas the latter pref ers the completely stacked conformation. We have done ab initio molecu lar orbital calculations and decomposition analyses of the intermolecu lar interaction energies to clarify the origin of the different stacki ng conformations. It was concluded that the main origin is the differe nce in the steric part of the interaction energies. (C) 1994 by John W iley and Sons, Inc.