TY  - JOUR
A1  - Baranac-Stojanovic, Marija
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Density Functional Calculations of the Anisotropic Effects of Borazine and 1,3,2,4-Diazadiboretidine
JF  - ChemPhysChem : a European journal of chemical physics and physical chemistry
N2  - On the basis of the nucleus-independent chemical shift (NICS) concept, the anisotropic effects of two inorganic rings, namely, borazine and planar 1,3,2,4-diazadiboretidine, are quantitatively calculated and visualized as isochemical shielding surfaces (ICSSs). Dissection of magnetic shielding values along the three Cartesian axes into contributions from s and p bonds by the natural chemical shieldingnatural bond orbital (NCSNBO) method revealed that their appearance is not a simple reflection of the extent of (anti)aromaticity.
KW  - anisotropic effects
KW  - aromaticity
KW  - B,N heterocycles
KW  - density functional calculations
KW  - NMR spectroscopy
Y1  - 2012
U6  - https://doi.org/10.1002/cphc.201200732
SN  - 1439-4235
VL  - 13
IS  - 17
SP  - 3803
EP  - 3811
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Baranac-Stojanovic, Marija
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Is the conventional interpretation of the anisotropic effects of C=C double bonds and aromatic rings in NMR spectra in terms of the p-electron shielding/deshielding contributions correct?
JF  - Chemistry - a European journal
N2  - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 angstrom away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C?C double bond or the aromatic ring should not be explained in terms of the conventionally accepted p-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
KW  - ab initio calculations
KW  - anisotropic effects
KW  - NMR spectroscopy
KW  - nucleus-independent chemical shift
KW  - pi interactions
Y1  - 2012
U6  - https://doi.org/10.1002/chem.201101882
SN  - 0947-6539
VL  - 18
IS  - 1
SP  - 370
EP  - 376
PB  - Wiley-Blackwell
CY  - Malden
ER  -