@article{BaranacStojanovicKochKleinpeter2012, author = {Baranac-Stojanovic, Marija and Koch, Andreas and Kleinpeter, Erich}, title = {Density Functional Calculations of the Anisotropic Effects of Borazine and 1,3,2,4-Diazadiboretidine}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {13}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {17}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201200732}, pages = {3803 -- 3811}, year = {2012}, abstract = {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.}, language = {en} } @article{BaranacStojanovicKochKleinpeter2012, author = {Baranac-Stojanovic, Marija and Koch, Andreas and Kleinpeter, Erich}, title = {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?}, series = {Chemistry - a European journal}, volume = {18}, journal = {Chemistry - a European journal}, number = {1}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0947-6539}, doi = {10.1002/chem.201101882}, pages = {370 -- 376}, year = {2012}, abstract = {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.}, language = {en} }