π-Molecular complexes: A modified CNDO study of the benzene-borazine system

Abstract

The standard CNDO/2 method is shown to be unable to produce meaningful potential curves for n-n-type molecular complexes. A modification of this method in which pairs of atoms associated with the same molecule and with different molecules are differentiated leads to reduced intermolecular bonding and provides reasonable stabilization energies and intermolecular separations. Calculations based on this modified method indicate that benzene-borazine and borazine-borazine complexes in which the molecules are symmetrically disposed in parallel planes can exist in the ground state. The stabilization energies are calculated to be in the range 2-5 kcal/mole for benzene-borazine and 5-18 kcal/mole for borazine-borazine, with interplanar separations near 3 A. in both cases.

Determination of resonance integrals for transanular interactions within semiempirical theories

“…( 2). This explains why Grein and Weiss [21] were forced to reduce in magnitude the interring resonance integrals with respect to the intraring integrals in a CNDO [22] study of the benzene-borazine complex in order to get sensible results. A CNDO study of [2.2] (1, 4)cyclophane by Duke et al [23] yielded the b3, orbital as highest one, quite in contrast to the experimental assignment [16].…”

Ab initiocalculations of multipole moments, polarizabilities and long-range interaction coefficients for the azabenzene molecules

“…Benzene, which has been studied frequently as a donor molecule in chargetransfer complexes with the aid of semi-empirical methods (for example, bondbond interactions [91,92], CNDO [93][94][95], PCILO [96]), has received less attention as a Van der Waals dimer, benzene-benzene. Except for the crystal studies [8,9,17] there exist the empirical model treatment of [18], the gas and liquid phase studies based on a six-centred Lennard-Jones potential of [97,98], the PCILO treatment of [19], which left some serious unsettled PCILO connected problems, and the ~r-rr calculations reported in [4,5,14].…”