NOVEL-APPROACH TO MOLECULAR SIMILARITY - 2ND-ORDER SIMILARITY INDEXESFROM GEMINAL EXPANSION OF PAIR DENSITIES

The recently introduced second-order similarity index g(AB) was genera lized by using the geminal and/or spingeminal expansion of pair densit ies that they are derived from. The comparison with previous related s tudies confirms that the generalization does increase the information content of new indices, especially in providing the information about the difference in the spin recoupling of pure singlet and triplet stat es of electron pairs. Analogously, as in previous studies, the approac h was applied to the analysis of several selected pericyclic reactions and possible mechanistic implications arising from the increased info rmation content are briefly discussed. (C) 1994 John Wiley & Sons, Inc .