Dynamically corrected ab initio minimum geometries and NMR chemical shifts for H bonded systems

Abstract

Anharmonic potential energy surfaces for the coordinates r(A–H) and r(A...B in the A–H...B H-bonds (H2O)2, HOHF-, and HOHOH- have been calculated ab initio. In addition, NMR nuclear shielding surfaces for the atoms A and B were calculated. The nuclear configuration interaction (CI) method was applied to achieve anharmonic vibrational states. These are the bases for the vibrationally averaged distances r(A–H) and r(A–D) as well as r(A...B) (H) and r(A...B) (D), and dynamically corrected NMR chemical shifts. Changes of interatomic distances and chemical shifts upon deuteration are presented and discussed. The maximum dynamical corrections are 0•09 Å for the OH distance in HOHOH- and 9 ppm for δ(19F) in HOHF-. The maximum deuteration effects are 0•018 Å for the OH distance and 3 ppm for the δ(19F) NMR chemical shift in HOHF-.