TY - BOOK A1 - Kleinpeter, Erich A1 - Klod, Sabrina A1 - Koch, Andreas T1 - Endohedral and external through-space shieldings of the fullerenes C50, C60, C60-6, C70, and C70-6- visualization of (Anti)aromaticity and their effects on the chemical shifts of encapsulated nuclei N2 - Endohedral and external through-space NMR shieldings (TSNMRS) and the magnetic susceptibilities of the fullerene carbon cages of C50, C60, C60-6, C70, and C70-6 were assessed by ab initio molecular orbital calculations. Employing the nucleus-independent chemical shift (NICS) concept, these TSNMRS were visualized as isochemical shielding surfaces (ICSS) and were applied to quantitatively estimate either the aromaticity or the anti-aromaticity on the fullerene surface pertaining to the five- or six-membered ring moieties and the shielding of any nuclei enclosed within the carbon cages. Differences between the NICSs calculated at the center of the fullerene carbon cages and the experimental chemical shifts of encapsulated NMR-active nuclei as well as experimental shieldings observed for different encapsulated nuclei were able to be understood readily for the first time. Y1 - 2008 UR - http://pubs.acs.org/doi/full/10.1021/jo702316h U6 - https://doi.org/10.1021/jo702316h ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Seidl, Peter R. T1 - Visualization and quantification of the anisotropic effect of C=C double bonds on 1H NMR spectra of highly congested hydrocarbons-indirect estimates of steric strain N2 - The anisotropic effect of the olefinic C=C double bond has been calculated by employing the NICS (nucleus independent chemical shift) concept and visualized as an anisotropic cone by a through space NMR shielding grid. Sign and size of this spatial effect on 1H chemical shifts of protons in norbornene, exo- and endo-2-methylnorbornenes, and in three highly congested tetracyclic norbornene analogs have been compared with the experimental 1H NMR spectra as far as published. 1H NMR spectra have also been calculated at the HF/6-31G* level of theory to get a full, comparable set of proton chemical shifts. Differences between ;(1H)/ppm and the calculated anisotropic effect of the C=C double bond are discussed in terms of the steric compression that occurs in the compounds studied. Y1 - 2008 UR - http://pubs.acs.org/doi/full/10.1021/jp801063t U6 - https://doi.org/10.1021/Jp801063t ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Sahoo, Himansu S. A1 - Chand, Dillip Kumar T1 - Anisotropic effect of the nitrate anion-manifestation of diamagnetic proton chemical shifts in the 1H NMR spectra of NO3-coordinated complexes N2 - The anisotropic effect of the planar nitrate anion NO3- has been ab initio calculated employing the Nucleus- Independent Chemical Shift (NICS) concept of von Ragué Schleyer and visualized as Iso-Chemical-Shielding Surfaces (ICSSs) of various (de)shieldings. Complexation-induced shifts in the 1H NMR spectra of nitrate/metal complexes or nitrate/receptor supramolecules can be separated now into anisotropic influences of the suitably coordinated nitrate anions and effects originating from differential sources. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040402008005814 U6 - https://doi.org/10.1016/j.tet.2008.03.063 ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Fettke, Anja A1 - Kleinpeter, Erich T1 - Push-pull vs captodative aromaticity N2 - Vinylogs of fulvalenes with cyclopropenyl and cyclopentadienyl moieties attached either to different carbon atoms (c-C3H2-CH-CH=C5H4-c, 7) or to the same carbon atom [X=C(c-C3H2)(c-C5H4), 10] [X = CH2; C(CN)2; C(NH2)2; C(OCH2)2; O; c-C3H2; c-C5H4; SiH2; CCl2] of the double bond inserted between the two rings are examined theoretically at the B3LYP/ 6;311G(d,p) level. Both types of compounds are shown to possess aromaticity, which was called "push;pull" and "captodative" aromaticity, respectively. For the captodative mesoionic structures X=C(c-C3H2)(c-C5H4), the presence of both the two aromatic moieties and the C=C double bond is the necessary and sufficient condition for their existence as energetic minima on the potential energy surface. Aromatic stabilization energy (ASE) was assessed by the use of homodesmotic reactions and heats of hydrogenation. Spatial magnetic criteria (through space NMR shieldings, TSNMRS) of the two types of vinylogous fulvalenes 7 and 10 have been calculated by the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept of Paul von Ragué; Schleyer, and visualized as iso-chemical-shielding surfaces (ICSS) of various sizes and directions. TSNMRS values can be successfully employed to visualize and quantify the partial push;pull and captodative aromaticity of both the three- and five-membered ring moieties. In addition, the push;pull effect in compounds 7 and 10 could be quantified by the occupation quotient ;*C=C/;C=C of the double bond inserted between the two rings. Y1 - 2008 UR - http://pubs.acs.org/loi/jpcafh U6 - https://doi.org/10.1021/jp804999m SN - 1089-5639 ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Quantification of the (Anti)Aromaticity of Fulvalenes Subjected to -Electron Cross-Delocalization N2 - Fulvalenes 3-12 were theoretically studied at the ab initio level of theory. For the global minima structures, the occupation of the bonding (pi)C=C orbital of the interring C=C double bond obtained by NBO analysis quantitatively proves pi-electron cross-delocalization resulting in, at least partially, 2- or 6pi-electron aromaticity and 8pi- electron antiaromaticity for appropriate moieties. The cross-conjugation was quantified by the corresponding occupation numbers and lengths of the interring C=C double bonds, while the aromaticity or antiaromaticity due to cross- delocalization of the pi-electrons was visualized and quantified by through-space NMR shielding surfaces. Y1 - 2008 UR - http://pubs.acs.org/doi/full/10.1021/jo701520j U6 - https://doi.org/10.1021/Jo701520j ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Mikhova, Bozhana A1 - Stamboliyska, Bistra A. A1 - Kolev, Tsonko M. T1 - Quantification of the push-pull character of the isophorone chromophore as a measure of molecular hyperpolarizability for NLO applications N2 - The push-pull character of a series of para-phenyl substituted isophorone chromophores has been quantified by the 13C chemical shift difference of the three conjugated partial C=C double bonds and the quotient of the occupations of both the bonding and anti-bonding orbitals of these C=C double bonds as well. The correlations of the two push-pull quantifying parameters, and to the corresponding bond lengths, strongly recommend ;*c=c/ ;c=c as the general parameter to estimate charge alternation and as a very useful indication of the molecular hyperpolarizabilities for NLO application of the compounds studied. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040403907025877 U6 - https://doi.org/10.1016/j.tetlet.2007.12.107 SN - 0040-4039 ER - TY - JOUR A1 - Neuvonen, Helmi A1 - Fulop, Ferenc A1 - Neuvonen, Kari A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Electronic effects of heterocyclic ring systems as evaluated with the aid of 13C and 15N NMR chemical shifts and NBO analysis N2 - The electronic effects of the 5- and 6-membered heterocyclic rings on the C=N-N unit of five different hydrazone derivatives of pyridine-2-, -3- and -4-carbaldehydes, pyrrole-2-carbaldehyde, furan-2- and -3-carbaldehydes and thiophene-2- and -3-carbaldehydes have been studied with the aid of 13C and 15N NMR measurements together with the natural bond orbital (NBO) analysis. As model compounds are used the corresponding substituted benzaldehyde derivatives. The polarization of the C=N unit of the hydrazone functionality of the heteroaryl derivatives occurs in an analogous manner with that of phenyl derivatives. The electron-withdrawing heteroaryl groups destabilize and the electron-donating groups stabilize the positive charge development at the CN carbon while the effect on the negative charge development is opposite. The 15N NMR chemical shift of the C=N and C=N-N nitrogens and the NBO charges at C=N-N unit can be correlated with the replacement substituent constants of the heteroaryl groups. 13C NMR shifts of the C=N carbon of N,N- dialkylhydrazones of the heteroarenecarbaldehydes can be correlated with a dual parameter equation possessing the polar substituent constant ;* of the heteroaryl group and the electronegativity of the heteroatom as variables. Y1 - 2008 UR - http://onlinelibrary.wiley.com/doi/10.1002/poc.1271/pdf U6 - https://doi.org/10.1002/Poc.1271 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Fettke, Anja T1 - Quantification of the (anti)aromaticity of fulvenes subject to ring size N2 - Tria-, penta-, hepta- and nonafulvenes (1-4) have been studied theoretically at the MP2 ab initio level of theory. For the global minimum structures, the occupation of the bonding ;C=C orbital of the exocyclic C=C double bond, obtained by NBO analysis, quantitatively proves ;-electron delocalization which can reveal partial 2-, 6- and 10-;-electron aromaticity, and 4-, 8- and 12-;-electron antiaromaticity of the ring moieties. Beside the corresponding occupation number, this conjugation was quantified by the length of the exocyclic C=C double bond whilst the (anti)aromaticity of the ring moieties of 1-4 was visualized and quantified by through space NMR shielding surfaces (TSNMRS). Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040403908003766 U6 - https://doi.org/10.1016/j.tetlet.2008.02.137 SN - 0040-4039 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Bölke, Ute A1 - Frank, Andrea T1 - Polar substituent effect of the ester group on conformational equilibria of O-mono-substituted cyclohexanesùthe para-substituent effect in cyclohexyl benzoates N2 - Together with the nonsubstituted reference compound, para-methoxy- and para-nitro cyclohexyl benzoates have been synthesized and their conformational equilibria studied by low temperature NMR spectroscopy and theoretical DFT calculations. The free energy differences ;G° between axial and equatorial conformers were examined with respect to polar substituent influences on the conformational equilibrium of O-mono-substituted cyclohexane. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040402008013082 U6 - https://doi.org/10.1016/j.tet.2008.07.024 ER - TY - JOUR A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Szatmári, István A1 - Fulop, Ferenc A1 - Kleinpeter, Erich T1 - Synthesis and conformational analysis of naphth[1,2-e][1,3]oxazino[4,3-a][1,3]isoquinoline and naphth[2,1- e][1,3]oxazino[4,3-a]isoquinoline derivatives N2 - Through the cyclization of 1-(;-hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinoline and 1-(;- hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinoline with formaldehyde, phosgene, p-nitrobenzaldehyde or p-chlorophenyl isothiocyanate, 8-substituted 10,11-dihydro-8H,15bH-naphth[1,2-e][1,3]oxazino[4,3-a]isoquinolines (3 and 4) and 10,11- dihydro-8H,15bH-naphth[2,1-e][1,3]oxazino[4,3-a]isoquinolines (15 and 16) were prepared. Conformational analysis of both the piperidine and the 1,3-oxazine moieties of these heterocycles by NMR spectroscopy and an accompanying theoretical study revealed that these two conformationally flexible six-membered ring moieties prefer twisted chair conformers. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040402008009150 U6 - https://doi.org/10.1016/j.tet.2008.05.025 ER -