TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - The anisotropic effect of functional groups in H-1 NMR spectra is the molecular response property of spatial NICS-the frozen conformational equilibria of 9-arylfluorenes
JF  - Tetrahedron
N2  - Rotation about the single bond adjoining the aryl and fluorene moieties in 9-arylfluorenes can be frozen out on the NMR timescale if methyl groups are located at either one or both of the ortho positions of the aryl substituent. In the ground-state of these rotamers, the planes of the aryl and fluorene moieties are perpendicular to each other and the methyl substituents are consequently positioned either above the fluorene moiety or in-plane with it; thus, the methyl protons are either shielded or deshielded, respectively, due to the ring current effect of the fluorene moiety. This anisotropic effect on the H-1 chemical shifts of the methyl protons has been quantified on the basis of through-space NMR shieldings (TSNMRS) and subsequently Delta delta(calcd) compared with the experimentally observed chemical shift differences, Delta delta(exp). In this context, the experimental anisotropic effects of functional groups in the H-1 NMR have proven to quantitatively be the molecular response property of theoretical spatial nucleus independent chemical shieldings (NICS). Differences between Delta delta(calcd) and Delta delta(exp) were, for the first time, also quantified as arising from steric compression.
KW  - Through-space NMR shieldings (TSNMRS)
KW  - Spatial NICS
KW  - Anisotropic effect
KW  - Iso-chemical-shielding surfaces (ICSS)
KW  - 9-Arylfluorenes
Y1  - 2011
U6  - https://doi.org/10.1016/j.tet.2011.06.005
SN  - 0040-4020
VL  - 67
IS  - 32
SP  - 5740
EP  - 5743
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - (Anti)aromaticity of dehydroannulenes of various ring size proved by the ring current effect in H-1 NMR spectra
JF  - Tetrahedron
N2  - The spatial magnetic properties (Through-Space NMR Shieldings-TSNMRS) of already synthesized dehydro[n]annulenes of various ring size (from C-12 to C-20) have been computed, visualized as Isochemical Shielding Surfaces (ICSS) of various size and direction, and were examined subject to present (anti)aromaticity. For this purpose the thus quantified ring current effect of the macro cycles on proximate protons in proton NMR spectra was employed.
KW  - Dehydro[n]annulenes
KW  - (Anti)aromaticity
KW  - TSNMRS
KW  - H-1 NMR spectroscopy
KW  - Anisotropic effect
KW  - Theoretical calculations
KW  - ICSS
Y1  - 2013
U6  - https://doi.org/10.1016/j.tet.2012.12.019
SN  - 0040-4020
VL  - 69
IS  - 5
SP  - 1481
EP  - 1488
PB  - Elsevier
CY  - Oxford
ER  -