NMR ¹H-Shielding Constants of Hydrogen-Bond Donor Reflect Manifestation of the Pauli Principle

Abstract

High Resolution Image Download MS PowerPoint Slide NMR spectroscopy is one of the most useful methods for detection and characterization of hydrogen bond (H-bond) interactions in biological systems. For H bonds X–H···Y, where X and Y are O or N, it is generally believed that a decrease in 1 H-shielding constants relates to a shortening of H-bond donor–acceptor distance. Here we investigated computationally the trend of 1 H-shielding constants for hydrogen-bonded protons in a series of guanine C8-substituted GC pair model compounds as a function of the molecular structure. Furthermore, the electron density distribution around the hydrogen atom was analyzed with the Voronoi deformation density (VDD) method. Our findings demonstrate that 1 H-shielding values of the hydrogen bond are determined by the depletion of charge around the hydrogen atom, which stems from the fact that electrons obey the Pauli exclusion principle.