@article{KleinpeterSchulenburgZugetal.2005,
  author    = {Kleinpeter, Erich and Schulenburg, Anja and Zug, Ines and Hartmann, Horst},
  title     = {The interplay of thio(seleno)amide/vinylogous thio(seleno)amide "Resonance" and the anisotropic effect of thiocarbonyl and selenocarbonyl functional groups},
  issn      = {0022-3263},
  year      = {2005},
  abstract  = {[GRAPHICS] Amino-substituted thio(seleno)acrylamides 1-4 were synthesized and their H-1 and C-13 NMR spectra assigned. Both the NMR data and the results of theoretical calculations at the ab initio level of theory were employed to elucidate the adopted structures of the compounds in terms of E/Z isomerism and s-cis/s-trans configuration. In the case of the asymmetrically N(Me)Ph-substituted compounds, ab initio GIAO-calculated ring current effects of the N-phenyl group were applied to successfully determine the preferred conformer bias. The restricted rotations about the two C-N partial double bonds were studied by DNMR and the barriers to rotation (Delta G(c)(double dagger)) determined at the coalescence temperatures, and these were discussed with respect to the structural differences between the compounds. The barriers to rotation were also calculated at the ab initio level of theory where the best results (R-2 = 0.8746) were obtained only with inclusion of the solvent at the SCIPCMHF/6-31G* level of theory. The calculations also provided means of assessing structural influences which were not available due to inaccessible rotation barriers. By means of natural bond orbital (NBO) analysis of 1-4, the occupation numbers of nitrogen lone pairs and bonding/antibonding pi/pi* orbitals were shown to quantitatively describe thio(seleno)amide/vinylogous thio(seleno)amide "resonance". Finally, the thio(seleno)carbonyl anisotropic effect was quantitatively calculated by the GIRO method and visualized by isochemical shielding surfaces (ICSS). Only marginal differences between the two anisotropic effects were calculated and are therefore of questionable utility for previous and future applications with respect to stereochemical assignments},
  language  = {en}
}
@article{KleinpeterSchulenburg2006,
  author    = {Kleinpeter, Erich and Schulenburg, Anja},
  title     = {Quantification of the push-pull effect in tolanes and a revaluation of the factors affecting the C-13 chemical shifts of the carbon atoms of the C=C triple bond},
  issn      = {0022-3263},
  doi       = {10.1021/Jo060199j},
  year      = {2006},
  abstract  = {Variously substituted tolanes were employed to show that the push-pull effect is also active in C equivalent to C triple bonds by the successful correlation of the occupation quotient pi*/pi of the pi orbital in resonance with the substituted phenyl moieties of tolanes versus the bond length of the C equivalent to C triple bond. In addition, the influences of the ortho phenyl ring substituents on the C-13 chemical shifts of the triple bond carbon atoms, which were estimated by Rubin et al.(4) to be "inapplicable for describing triple bond polarization", were re-evaluated, leading to the conclusion that, while anisotropic effects of ortho substituents are negligible, the steric ortho-substituent effects do in fact dominate the deviations obtained. A detailed theoretical NBO/NCS study has been employed to illuminate the facts of this case},
  language  = {en}
}