NMR CHEMICAL-SHIFTS - 1 - THE ROLE OF RELATIVE ATOMIC ORBITAL PHASE IN DETERMINING THE SIGN OF THE PARAMAGNETIC TERMS - CLF, CH3F, CH3NH3-CF(, FNH3+, AND HC)

Authors
WIBERG KB HAMMER JD ZILM KW CHEESEMAN JR KEITH TA
Citation
Kb. Wiberg et al., NMR CHEMICAL-SHIFTS - 1 - THE ROLE OF RELATIVE ATOMIC ORBITAL PHASE IN DETERMINING THE SIGN OF THE PARAMAGNETIC TERMS - CLF, CH3F, CH3NH3-CF(, FNH3+, AND HC), The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 102(45), 1998, pp. 8766-8773
Citations number
15
Categorie Soggetti
Chemistry Physical
Journal title
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory → ACNP
ISSN journal
10895639
Volume
102
Issue
45
Year of publication
1998
Pages
8766 - 8773
Database
ISI
SICI code
1089-5639(1998)102:45<8766:NC-1-T>2.0.ZU;2-1
Abstract
The shielding of several nuclei for molecules in magnetic fields was e xamined via B3LYP/6-311+G(3df, 3pd) calculations using the MP2/6-31G geometries. Both the gauge-invariant atomic orbital (GIAO) and individ ual gauges for atoms in molecules (IGAIM) methods were employed, and t he molecules were the isoelectronic series F-2, ClF, CH3F, CH3NH3+, FN H3+, and FC=CH. The main paramagnetic contributions arose from the pi and pi' molecular orbitals (MOs) interacting with the sigma MO. The p i interaction leads to deshielding in all cases. However, for the pi' MO in which the two p atomic orbitals have opposite phase, one nucleus is deshielded but the other is shielded. This appears to be a general phenomenon.