A comparative study of the calculation of Co-59 NMR shielding constants of hexacoordinated diamagnetic Co(III) complexes using DFT-IGLO and DFT-GIAO methods

A comparison between the DFT-IGLO and the DFT-GIAO shielding calculation methods is carried out using Co-59 chemical shifts of hexacoordinated diamagnetic cobalt(III) complexes as probes. The results show that the DFT-GIAO method produces shielding constants in better agreement with the experimental values when the same exchange correlation (XC) functional (BECKE/PERDEW) and basis sets are used. It is also shown that the use of the B3LYP XC functional in DFT-GIAO improves the Co-59 Shielding calculation results for 13 Co(III) complexes to <30% deviation to the experimental values for the first time. The calculated chemical shielding range covers 11000 ppm. (C) 1997 Elsevier Science B.V.