Theoretical investigations of the C-H...N interactions and molecular electrostatic potentials: aza derivatives of cubane

Weak C-H...N interactions, which are electrostatic in nature, in a series of aza derivatives of cubane, (CH)(8) (-) N-alpha(alpha) (alpha = 1-7) have been investigated by employing the ab initio and hybrid density functional methods. The characteristics of interactions have been analyzed using the topography of the molecular electrostatic potential, which reveal shallow minima near nitrogen on encompassing from the lowest energy isomers of azacubane to heptaazacubane. From the natural bond orbital analysis it has been shown that nitrogen lone pair localization increases on encompassing from aza to heptaazacubane. Consequent C-H stretching frequencies, particularly their red and blue shifts, have been discussed. (C) 2004 Elsevier B.V. All rights reserved.