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

Abstract

NMRspectroscopy is one of the most useful methods for detection andcharacterization 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 adecrease of 1H-shielding constants relates to a shortening of H-bondsdonor-acceptor distance. Here, we investigated computationally the trend of1H-shielding constants for hydrogen-bonded protons in a series of GuanineC8-substituted GC pair model compounds as a function of the molecularstructure. Furthermore, the electron density distribution around the hydrogenatom was analyzed with the Voronoi deformation density (VDD) method. Ourfindings demonstrate that 1H-shielding values of the hydrogen bond aredetermined by the depletion of charge around the hydrogen atom which stems fromthe fact that electrons obey the Pauli exclusion principle.