Three-dimensional molecular illustrations II: Isoelectrostatic energy contour spheres of influence applied to narcotic molecules.

A computer-generated method using quantum mechanics was applied to the calculation and subsequent plotting of nonperspective three-dimensional illustrations of molecules in vacuo. The purpose was to generate isoelectrostatic energy contour spheres for larger molecules and current drugs. The molecules chosen, morphine, meperidine, and alphaprodine, possess similar pharmacological properties. Minor configurational manipulation of meperidine and alphaprodine molecules was made to approximate the spatial configuration of the rigid morphine molecule so that direct comparisons were possible. Common areas of reactivity, potential energy minima, net atomic charges, spatial regions, and near neighbor influences are considered.

Three-dimensional molecular illustrations I: Isoelectron density contours and isoelectrostatic energy contours.

A method of depicting dimensional illustrations of molecules in vacuo that are sensitive to small electronic perturbations was attempted. This method would be useful in determining the effects of either perturbing groups from other molecules or changes produced by the addition or modification of an existing atom or chemical group on the same molecule. Isoelectron density contours for small molecules such as benzene, ammonia, and formaldehyde were first considered using the CNDO/2 molecular approximation method and then extended to the use of deorthogonalized CNDO/2 eigenvectors. These methods were similar in molecular projections but insensitive to electronic alterations. Therefore, the electrostatic potential energy was considered in developing contour surfaces of several of the molecules studied. In this case, acute and visually discernible changes were evidenced by electron exchange in the three-dimensional illustration of formaldehyde. The effect on the two-dimensional contour map of ammonia was strikingly altered by the addition of a proton, further substantiating the sensitivity of electrostatic contours to perturbing influences. These methods are considered and amplified in this report.