Premium
Thermal Effects and Vibrational Corrections to Transition Metal NMR Chemical Shifts
Author(s) -
Grigoleit Sonja,
Bühl Michael
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400256
Subject(s) - vanadium , chemical shift , chemistry , transition metal , titanium , density functional theory , metal , manganese , computational chemistry , electromagnetic shielding , ligand (biochemistry) , bond length , molecule , inorganic chemistry , materials science , organic chemistry , biochemistry , receptor , catalysis , composite material
Both zero‐point and classical thermal effects on the chemical shift of transition metals have been calculated at appropriate levels of density functional theory for a number of complexes of titanium, vanadium, manganese and iron. The zero‐point effects were computed by applying a perturbational approach, whereas classical thermal effects were probed by Car–Parrinello molecular dynamics simulations. The systematic investigation shows that both procedures lead to a deshielding of the magnetic shielding constants evaluated at the GIAO‐B3 LYP level, which in general also leads to a downfield shift in the relative chemical shifts, δ . The effect is small for the titanium and vanadium complexes, where it is typically on the order of a few dozen ppm, and is larger for the manganese and iron complexes, where it can amount to several hundred ppm. Zero‐point corrections are usually smaller than the classical thermal effect. The pronounced downfield shift is due to the sensitivity of the shielding of the metal centre with regard to the metal–ligand bond length, which increase upon vibrational averaging. Both applied methods improve the accuracy of the chemical shifts in some cases, but not in general.