@article{KleinpeterKoch2021,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Dative or coordinative carbon-boron bond in boron trapped N-heterocyclic carbenes (NHCs)?},
  series = {Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry},
  volume    = {80},
  journal   = {Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2020.131787},
  pages     = {8},
  year      = {2021},
  abstract  = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of isolated as well as B-C bond length varied model compounds (BR3 trapped NHCs) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the present dative vs. coordinative bond character of the boron-carbon bond in the trapped NHCs. Results are confirmed by bond lengths and B-11/C-13 chemical shift variations in the BR3 trapped NHCs.},
  language  = {en}
}
@article{KleinpeterKoch2021,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Intramolecular carbene stabilization via 3c,2e bonding on basis of the magnetic criterion},
  series = {Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry},
  volume    = {95},
  journal   = {Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry},
  publisher = {Elsevier Science},
  address   = {Amsterdam},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2021.132357},
  pages     = {9},
  year      = {2021},
  abstract  = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of bent cyclobutylcarbene 8, 1,2-diboretane-3-ylidene 9, and some carbene analogues of boron 14-18 as most intriguing examples of carbenes, which can be stabilized as homoaromatic systems with 3c,2e bonding, have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually, ring current effect/anisotropy effects as measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the degree of present 3c,2e-homoaromaticity. Results are confirmed by geometry (bond angles and bond lengths) and spectroscopic data, the delta(B-11)/ppm data and the C-13 chemical shifts of the carbene electron-deficient centre.},
  language  = {en}
}
@article{KleinpeterKoch2018,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Paramagnetic ring current effects in anti-aromatic structures subject to substitution/annelation quantified by spatial magnetic properties (TSNMRS)},
  series = {Tetrahedron},
  volume    = {74},
  journal   = {Tetrahedron},
  number    = {7},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2017.12.020},
  pages     = {700 -- 710},
  year      = {2018},
  abstract  = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of the typically anti-aromatic cyclopentadienyl cation, cyclobutadiene, pentalene, s-indacene and of substituted/annelated analogues of the latter structures have been calculated using the CIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to visualize and quantify the dia(para) magnetic ring current effects in the studied compounds. The interplay of dia(para)magnetic ring current effects due to substitution/annelation caused by heavy exo-cyclic n,pi-electron delocalization can be qualified.},
  language  = {en}
}
@article{KleinpeterKoch2019,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Is the term "Carbene" justified for remote N-heterocyclic carbenes (r-NHCs) and abnormal N-heterocyclic carbenes (aNHCs/MICs)?},
  series = {Tetrahedron},
  volume    = {75},
  journal   = {Tetrahedron},
  number    = {11},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2019.02.005},
  pages     = {1548 -- 1554},
  year      = {2019},
  abstract  = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of typical N-heterocyclic carbenes NHCs, r-NHCs, a-NHCs and MICs have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. Prior to that both structures and 13C chemical shifts were calculated and in case of isolated carbenes the computed δ(13C)/ppm values compared (as a quality criterion for obtained structures) with the experimental ones. The TSNMRS values of the studied carbenes, which are in mesomeric equilibrium with zwitterionic (ylide/betaine/mesoionic) resonance contributors, are employed to qualify and quantify the present electronic structure and if the term carbene is still justified to denote the compounds studied. The results, thus obtained from spatial magnetic properties (TSNMRS), are compared with the geometry of the compounds, the corresponding WIBERG's bond index values, and the 13C chemical shifts especially of the carbene electron-deficient centre.},
  language  = {en}
}
@article{KleinpeterKoch2019,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Benzyne - an acetylene- or cumulene-like electronic structure?},
  series = {Tetrahedron},
  volume    = {75},
  journal   = {Tetrahedron},
  number    = {33},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2019.07.011},
  pages     = {4663 -- 4668},
  year      = {2019},
  abstract  = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzyne 1 and analogues (benzene 2, 1,2,3-cyclohexatriene 3, cyclohexen-3-yne 4, cyclohexen-4-yne 5, cyclohexyne 6) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values could be employed to compare the diatropic ring current effects of benzene and benzyne, and, when compared with the spatial magnetic properties of the analogues, to answer the question whether the benzyne electronic structure is more acetylene- or cumulene-like, supported by structural data and delta(C-13)/ppm values. (C) 2019 Published by Elsevier Ltd.},
  language  = {en}
}
@article{KleinpeterKoch2017,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Identification of mesomeric substructures by through-space NMR shieldings (TSNMRS). Trimethine cyanine/merocyanine-like or aromatic pi-electron delocalization?},
  series = {Tetrahedron},
  volume    = {73},
  journal   = {Tetrahedron},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2017.05.062},
  pages     = {4265 -- 4274},
  year      = {2017},
  abstract  = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of amino-substituted heteraromatic six-membered ring systems such as pyrylium/thiopyrylium analogues have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to quantify and visualize the existing aromaticity of the studied compounds. Due to strong conjugation of six-membered ring pi-electrons and lone pairs of the exo-cyclic amino substituents (restricted rotation about partial C,N double bonds) the interplay of still aromatic and already dominating trimethine cyanine/merocyanine-like substructures can be estimated. (C) 2017 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{KleinpeterKoch2012,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Spatial magnetic properties subject to lone pair and pi electron delocalization in benzenoid and quinoid structures are quinoid tautomers really nonaromatic?},
  series = {Arkivoc : free online journal of organic chemistry},
  journal   = {Arkivoc : free online journal of organic chemistry},
  publisher = {ARKAT},
  address   = {Gainesville},
  issn      = {1551-7004},
  pages     = {94 -- 108},
  year      = {2012},
  abstract  = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzenoid and quinoid tautomeric structures such as benzodifurantrione and phenazine-type molecules have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept of Paul von Rague Schleyer and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to quantify and visualize the partial aromaticity of the studied compounds. In the case of the surprisingly more stable quinoid tautomers, the aromaticity-synonymous with stability due to the conjugation of p electrons and lone pairs-was not found to be particularly reduced.},
  language  = {en}
}