@article{KleinpeterKoch2013,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {(Anti)aromaticity of dehydroannulenes of various ring size proved by the ring current effect in H-1 NMR spectra},
  series = {Tetrahedron},
  volume    = {69},
  journal   = {Tetrahedron},
  number    = {5},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2012.12.019},
  pages     = {1481 -- 1488},
  year      = {2013},
  abstract  = {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.},
  language  = {en}
}
@article{KleinpeterWernerKoch2013,
  author    = {Kleinpeter, Erich and Werner, Peter and Koch, Andreas},
  title     = {Push-pull allenes-conjugation, (anti)aromaticity and quantification of the push-pull character},
  series = {Tetrahedron},
  volume    = {69},
  journal   = {Tetrahedron},
  number    = {11},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2013.01.027},
  pages     = {2436 -- 2445},
  year      = {2013},
  abstract  = {Structures, H-1/C-13 chemical shifts, and pi electron distribution/conjugation of an experimentally available and theoretically completed set of push-pull allenes Acc(2)C=C=CDon(2) (Acc=F, CHO, CF3, C N; Don=t-Bu, OMe, OEt, SMe, SEt, NCH2R) have been computed at the OFT level of theory. Both orthogonal linear and orthogonal bent structures have been obtained. In the latter case the push-pull character could be quantified by the quotient method. The C-13 chemical shift of the central allene carbon atom C-2 and chemical shift differences Delta delta(C-1, C-2) and Delta delta(C-2, C-3) of allene carbon atoms proved to be a quantitative alternative. TSNMRS of ring-closed push-pull allenes have been computed in addition and were employed to identify polar, carbene-like and carbone-like canonical structures of these molecules.},
  language  = {en}
}
@article{NeuvonenNeuvonenKochetal.2013,
  author    = {Neuvonen, Kari and Neuvonen, Helmi and Koch, Andreas and Kleinpeter, Erich},
  title     = {Nature of the steric Omega(S), E-R and E-S ' substituent constants - comparison with the aid of NBO and STERIC analysis},
  series = {Computational and theoretical chemistry},
  volume    = {1015},
  journal   = {Computational and theoretical chemistry},
  number    = {4},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2210-271X},
  doi       = {10.1016/j.comptc.2013.03.025},
  pages     = {34 -- 43},
  year      = {2013},
  abstract  = {The nature of the major steric substituent constant scales for alkyl substituents, i.e. Omega(S), E-R and E-S' scales, was studied with the aid of the NBO and the natural steric (STERIC) analyses. Cyclohexyl esters R-3-CCOOC6H11 (R = alkyl or H) were used as the model compounds. Special emphasis was laid on the potential contribution of the polar component in these steric substituent parameters. In the light of our model the Omega(S) scale seems to be dominantly a steric substituent constant scale as is seen on the strengths of the good correlation between the Omega(S) constants of the CR3 group and the total steric exchange energy values E-TSEE for the model compounds. However, the Omega(S) values also seem to include a minor electronic component due to the varying electrostatic effect via the C alpha atom. On the other hand, E-R and E-S' parameters largely hinge on the size dependent polar effect of the CR3 alkyl group. By way of our model this repulsive interaction can be quantified by descriptor Delta q(OCO), the natural charge difference q(C)(C=O) - Sigma qO for the O-C(=O) functional group. Delta q(OCO) depends on the E-TSEE values, on qC alpha and on the polarization coefficients of the oxygen hybrid in the NBO of the pi(C=O) bond. The size sensitivity of the kinetic E-S' constants can be connected to variation of the Burgi-Dunitz angle in the transition state for the standard reaction used. A comparison is made for the q(C)(C=O) or Delta q(OCO) values computed on the one hand with the NBO formalism and on the other hand with the Hirshfeld formalism. A practical novel substituent constant q(C)(C=O) for the size of the alkyl groups is introduced.},
  language  = {en}
}
@article{SzatmariHeydenreichKochetal.2013,
  author    = {Szatmari, Istvan and Heydenreich, Matthias and Koch, Andreas and Fulop, Ferenc and Kleinpeter, Erich},
  title     = {Unexpected isomerization of new naphth[1,3]oxazino[2,3-a] isoquinolines in solution, studied by dynamic NMR and supported by theoretical DFT computations},
  series = {Tetrahedron},
  volume    = {69},
  journal   = {Tetrahedron},
  number    = {35},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2013.06.094},
  pages     = {7455 -- 7465},
  year      = {2013},
  abstract  = {Through the reactions of 1-aminomethyl-2-naphthol and substituted 1-aminobenzyl-2-naphthols with 3,4-dihydroisoquinoline or 6,7-dimethoxy-3,4-dihydroisoquinoline under microwave conditions, naphth[1,2-e][1,3]oxazino[2,3-a]-isoquinoline derivatives were prepared in good yields. The latter reaction was extended by using 2-aminoarylmethyl-1-naphthols, leading to isomeric naphth-[2,1-e][1,3]oxazino[2,3-a] isoquinolines. Beside the detailed NMR spectroscopic and theoretical study of both stereochemistry and dynamic behaviour of these new conformational flexible heterocyclic ring systems an unexpected dynamic process between two diastereomers was observed in solution, studied by variable temperature H-1 NMR spectroscopy and the mechanism proved by theoretical DFT computations.},
  language  = {en}
}
@article{RasovicKochKleinpeteretal.2013,
  author    = {Rasovic, Aleksandar and Koch, Andreas and Kleinpeter, Erich and Markovic, Rade},
  title     = {Studies of the regioselective ring-opening closing mode of functionally different thiazolidine type enaminones - en route to the synthesis of trithiaazapentalene derivatives},
  series = {Tetrahedron},
  volume    = {69},
  journal   = {Tetrahedron},
  number    = {51},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2013.10.088},
  pages     = {10849 -- 10857},
  year      = {2013},
  abstract  = {Trithiaazapentalene derivatives were prepared by the reaction of 2-alkylidene-4-oxothiazolidines with Lawesson's reagent. They are classified as two structurally different trithiaazapentalene compounds that have different contributions of monocyclic 1,2-dithiole and 1,2,4-dithiazole structures and degrees of aromaticity of the bicyclic trithiaazapentalene system. The electron-donating ability of substituents at the C(5) position of the trithiaazapentalene system is recognized as the main cause for changes in pi-Celectron distribution. This is the first complete study of substituent effects on the structure of trithiapentalenes. (C) 2013 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?},
  issn      = {1551-7004},
  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}
}
@article{CsuetoertoekiSzatmariKochetal.2011,
  author    = {Cs{\"u}t{\"o}rt{\"o}ki, Ren{\´a}ta and Szatm{\´a}ri, Istv{\´a}n and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc},
  title     = {Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives},
  issn      = {0040-4020},
  year      = {2011},
  language  = {en}
}
@article{KleinpeterKoch2011,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Chelatoaromaticity-existing: yes or no? An answer given by spatial magnetic properties (through space NMR shieldings-TSNMRS)},
  issn      = {1463-9076},
  year      = {2011},
  language  = {en}
}
@article{KleinpeterKoch2011,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {The anisotropic effect of functional groups in 1H NMR spectra is the molecular response property of spatial NICS-the frozen conformational equilibria of 9-arylfluorenes},
  issn      = {0040-4020},
  year      = {2011},
  abstract  = {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 protons are either shielded or deshielded, respectively, due to the ringe current effect of the fluorene moiety. This anisotropic effect on the 1H chemical shifts of the methyl protons has been quantified on the basis of through- space NMR shieldings (TSNMRS) and subsequently _______ compared with the experimentally observed chemical shift differences _____. In this context, the experimental anisotropic effects of functional groups in the !H NMR have proven to quantitatively be the molecular response property of theoretical spatial nucleus independent chemical shieldings (NICS). Differences between _______ and _____ were, for the first time, also quantified as arising from steric compression.},
  language  = {en}
}
@article{KleinpeterHeydenreichKochetal.2012,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Koch, Andreas and Linker, Torsten},
  title     = {Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer},
  issn      = {0040-4020},
  year      = {2012},
  abstract  = {The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by 1H and 13C NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial/equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount.},
  language  = {en}
}
@article{KleinpeterCsuetoertoekiSzatmarietal.2012,
  author    = {Kleinpeter, Erich and Cs{\"u}t{\"o}rt{\"o}ki, Ren{\´a}ta and Szatm{\´a}ri, Istv{\´a}n and Koch, Andreas and Fulop, Ferenc},
  title     = {Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-ones},
  year      = {2012},
  abstract  = {The syntheses of naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-one derivatives (3a-f) were achieved by the solvent-free heating of benzyloxycarbonyl-protected intermediates (2a-f) with MeONa. For intermediates 2a-f, prepared by the reactions of substituted aminonaphthols with benzyl N-(2-formylphenyl)carbamate, not only the expected trans ring form B and chain form A1, but also the rearranged chain form A2 as a new tautomer were detected in DMSO at room temperature. The quantity of A2 in the tautomeric mixture was changed with time. Conformational analyses of the target heterocycles 3a-f by NMR spectroscopy and accompanying theoretical calculations at the DFT level of theory revealed that the oxazine ring preferred a twisted chair conformation and the quinazolone ring was planar. Besides the conformations, both the configurations at C-7a and C-15 and the preferred rotamers of the 1-naphthyl substituent at C-15 were assigned, which allowed evaluation of the aryl substituent-dependent steric hindrance in this part of the molecules. Configurational assignments were corroborated by quantifying the ring current effect of 15-aryl in terms of spatial NICS.},
  language  = {en}
}
@article{KleinpeterCsuetoertoekiSzatmarietal.2012,
  author    = {Kleinpeter, Erich and Cs{\"u}t{\"o}rt{\"o}ki, Ren{\´a}ta and Szatm{\´a}ri, Istv{\´a}n and Heydenreich, Matthias and Koch, Andreas and Starke, Ines and Fulop, Ferenc},
  title     = {Novel piperidine-fused benzoxazino- and quinazolinonaphthoxazines-synthesis and conformational study},
  issn      = {0040-4020},
  year      = {2012},
  abstract  = {The reactions of 1-(amino(2-hydroxyphenyl)methyl)-2-naphthol (3) and 1-(amino(2-aminophenyl)methyl)-2-naphthol (6) with glutardialdehyde resulted in the formation of piperidine-fused benzoxazinonaphthoxazine 4 and quinazolinonaphthoxazine 7, respectively, both in diastereopure form. The full conformational search protocols of 4 and 7 were successfully carried out by NMR spectroscopy and accompanying molecular modelling; the global minimum-energy conformers of all diastereomers were computed, and the assignments of the most stable stereoisomers, Gtct1 for 4 and Gtct1 for 7, were corroborated by spatial NOE information relating to the H7a-H10a-H15b and H,H coupling patterns of the protons in the flexible part of the piperidine moiety. Additionally, mass spectrometric fragmentation was investigated in collision-induced dissociation experiments. The elemental compositions of the ions were determined by accurate mass measurements.},
  language  = {en}
}
@article{KleinpeterBalciYaparetal.2012,
  author    = {Kleinpeter, Erich and Balci, Kubilay and Yapar, G. and Akkaya, S. and Akyuz, S. and Koch, Andreas},
  title     = {A conformational analysis and vibrational spectroscopic investigation on 1,2-bis(o-carboxyphenoxy) ethane molecule},
  year      = {2012},
  abstract  = {The minima on the potential energy surface of 1,2-bis(o-carboxyphenoxy) ethane (CPE) molecule in its electronic ground state were searched by a molecular dynamics simulation performed with MM2 force field. For each of the found minimum-energy conformers, the corresponding equilibrium geometry, charge distribution, HOMO-LUMO energy gap, force field, vibrational normal modes and associated IR and Raman spectral data were determined by means of the density functional theory (DFT) based electronic structure calculations carried out by using B3LYP method and various Pople- style basis sets. The obtained theoretical data confirmed the significant effects of the intra- and inter-molecular hydrogen bonding interactions on the conformational structure, force field, and group vibrations of the molecule. The same data have also revealed that two of the determined stable conformers, both of which exhibit pseudo-crown structure, are considerably more favorable in energy to the others and accordingly provide the major c ntribution to the experimental spectra of CPE. In the light of the improved vibrational spectral data obtained within the "SQM FF" methodology and "Dual Scale Factors" approach for the monomer and dimer forms of these two conformers, a reliable assignment of the fundamental bands observed in the experimental room-temperature IR and Raman spectra of the molecule was given, and the sensitivities of its group vibratb20s to conformation, substitution and dimerization were discussed.},
  language  = {en}
}
@article{KleinpeterBranacStojanoviKoch2012,
  author    = {Kleinpeter, Erich and Branac-Stojanovi, Marija and Koch, Andreas},
  title     = {Is the Conventional Interpretation of the Anisotropic Effects of CC Double Bonds and Aromatic Rings in NMR Spectra in Terms of the -Electron Shielding/Deshielding Contributions Correct?},
  issn      = {1521-3765},
  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;{\AA} 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 ;-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.},
  language  = {en}
}
@article{KleinpeterNeuvonenNeuvonenetal.2011,
  author    = {Kleinpeter, Erich and Neuvonen, Kari and Neuvonen, Helmi and Koch, Andreas},
  title     = {NBO analysis of polar and steric effect using the axial-equatorial equilibrium of cyclohexyl acetates as a probe},
  issn      = {2210-271X},
  year      = {2011},
  language  = {en}
}
@article{KleinpeterNeuvonenNeuvonenetal.2012,
  author    = {Kleinpeter, Erich and Neuvonen, Kari and Neuvonen, Helmi and Koch, Andreas},
  title     = {Taft equation in the light of NBO computations : Introduction of a novel polar computational substituent constant scale for alkyl groups},
  issn      = {2210-271X},
  year      = {2012},
  language  = {en}
}
@article{KleinpeterPihlajaSinkkonenetal.2011,
  author    = {Kleinpeter, Erich and Pihlaja, Kalevi and Sinkkonen, Jari and St{\´a}jer, Gez{\´a} and Koch, Andreas},
  title     = {1-Oxo-1,3-dithiolanes{\`u}synthesis and stereochemistry},
  issn      = {0749-1581},
  year      = {2011},
  abstract  = {1-Oxo-1,3-dithiolane (4) and its cis- andtrans-2-methyl (5,6), -4-methyl (7,8) and -5-methyl (9,10) derivatives were prepared by oxidizing the corresponding 1,3-dithiolanes (1-3) with NaIO4 in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with 1H and 13C NMR spectroscopy and molecular modelling. The sulfoxides 4-6 and 8-10 attain two S(1) type envelopes (sometimes slightly distorted) the S=Oax envelope greatly dominating. Cis-4-methyl-1-oxo-1,3-dithiolane is a special case exhibiting both two closely related S=Oax (30 and 27\%) as well as S=Oeq (21 and 22\%) forms [S(1) and C(4) envelopes, respectively]. The relative energies of these conformations, the values of 1H-1H coupling constants and 1H and 13C chemical shifts were estimated by computational methods and they support well the conclusions based on the experimental data.},
  language  = {en}
}
@book{KleinpeterKlodKoch2008,
  author    = {Kleinpeter, Erich and Klod, Sabrina and Koch, Andreas},
  title     = {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},
  doi       = {10.1021/jo702316h},
  year      = {2008},
  abstract  = {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.},
  language  = {en}
}
@article{KleinpeterKochSeidl2008,
  author    = {Kleinpeter, Erich and Koch, Andreas and Seidl, Peter R.},
  title     = {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},
  doi       = {10.1021/Jp801063t},
  year      = {2008},
  abstract  = {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.},
  language  = {en}
}
@article{KleinpeterKochSahooetal.2008,
  author    = {Kleinpeter, Erich and Koch, Andreas and Sahoo, Himansu S. and Chand, Dillip Kumar},
  title     = {Anisotropic effect of the nitrate anion-manifestation of diamagnetic proton chemical shifts in the 1H NMR spectra of NO3-coordinated complexes},
  doi       = {10.1016/j.tet.2008.03.063},
  year      = {2008},
  abstract  = {The anisotropic effect of the planar nitrate anion NO3- has been ab initio calculated employing the Nucleus- Independent Chemical Shift (NICS) concept of von Ragu{\´e} 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.},
  language  = {en}
}
@article{deAraujoChaconCarneiroetal.2010,
  author    = {de Araujo, Martha T. and Chacon, Eluzir P. and Carneiro, Jos{\´e} W. de M. and Koch, Andreas and Kleinpeter, Erich},
  title     = {Analysis of anisotropic effects in trinuclear metal carbonyl compounds by visualization of through-space NMR shielding},
  issn      = {1610-2940},
  doi       = {10.1007/s00894-010-0662-3},
  year      = {2010},
  abstract  = {Through-space NMR shieldings were calculated for trinuclear metal-carbonyl compounds [M-3(CO)(12)] (M = Fe, Ru, Os), employing the nucleus-independent chemical shift approach. The through-space shieldings were visualized as a contour plot of iso-chemical shielding surfaces, and were applied to quantify the overall anisotropic effect of the carbonyl groups, as well as to identify the influence of the transition metal on the scopes of the corresponding anisotropy cones. The shielding surfaces show that the anisotropic effect of the carbonyl groups at equatorial positions changes depending on the metal. This effect was associated with pi-backdonation from the metal to the carbonyl groups in that position, in agreement with geometric data as well as calculated NMR parameters. Therefore, visualization of the through-space NMR shieldings of trinuclear metal-carbonyl compounds of group 8 is able to reflect the distinct arrangements of the carbonyl groups in these organometallic compounds.},
  language  = {en}
}
@article{AwadConradKochetal.2010,
  author    = {Awad, Duha Jawad and Conrad, Franziska and Koch, Andreas and Schilde, Uwe and Poeppl, Andreas and Strauch, Peter},
  title     = {1,10-phenanthroline-dithiolate mixed ligand transition metal complexes : synthesis, characterization and EPR spectroscopy},
  issn      = {0020-1693},
  doi       = {10.1016/j.ica.2010.01.021},
  year      = {2010},
  abstract  = {A series of new N2S2 mixed ligand transition metal complexes, where N-2 is phenanthroline and S-2 is 1,2- dithiooxalate (dto) or 1,2-dithiosquarate (dtsq), has been synthesized and characterized. IR spectra reveal that the 1,2- dithiolate ligands are coordinated via the sulfur atoms forming a N2S2 coordination sphere. The copper(II) complex [Cu(phen)(dto)] was studied by EPR spectroscopy as a diamagnetically diluted powder. The diamagnetic dilution resulted from doping of the copper complex into the isostructural host lattice of the nickel complex [Ni(phen)(dto)]. The electronic situation in the frontier orbitals of the copper complex calculated from the experimental data is compared to the results of EHT and DFT calculations. Furthermore, one side product, chlorobis(1,10-phenanthroline)copper(I) ethanol solvate hydrate [(phen)(2)CuCl]center dot C2H5OH center dot H2O, was formed by a reduction process and characterized by X-ray diffraction. In the crystal packing one-dimensional columns of dimers are formed, stabilized by significant pi-pi interactions.},
  language  = {en}
}
@article{BoehmTomašcikovaImrichetal.2009,
  author    = {Boehm, Stanislav and Tomašcikov{\´a}, Jana and Imrich, J{\´a}n and Danihel, Ivan and Kristian, Pavol and Koch, Andreas and Kleinpeter, Erich and Klika, Karel D.},
  title     = {Computational study to assign structure, tautomerism, E/Z and s-cis/s-trans isomerism, pi-delocalization, partial aromaticity, and the ring size of 1,3-thiazolidin-4-ones and 1,3-thiazin-4-ones formed from thiosemicarbazides},
  issn      = {0166-1280},
  doi       = {10.1016/j.theochem.2009.09.019},
  year      = {2009},
  abstract  = {A set of structures encompassing 1-(9-acridinyl)thiosemicarbazide and its 2-methyl derivative together with their various tautomeric structures; the 5-membered ring 1,3-thiazolidin-4-one products resulting from the reaction of 1- (9-acridinyl)thiosemicarbazide and its 2-methyl derivative with dimethyl acetylenedicarboxylate (DMAD) together with the alternative 6-membered ring isomeric reaction products as well as other potential isomeric structures; and the 6- membered ring 1,3-thiazin-4-one product resulting from the reaction of 2-methyl-1-(9-acridinyl)thiosemicarbazide with methyl propiolate (MP) together with the alternative 5-membered ring isomeric reaction product were all extensively studied by molecular modeling calculations using DFT at the B3LYP/6-31G(d,p) level of theory. The ring-chain tautomerism of the thiosemicarbazides, the regio- and stereoselectivity of the reactions, the adopted conformations and E/Z configurations of the products, the prototropic tautomerism of all the compounds, and the reasons for the predominance of the s-cis conformation of the Z configuration of the 1,3-thiazolidin-4-one product in particular were all extensively analyzed. Comparison of the modeled structures were also made to the 1,3-thiazolidin-4-one and 1,3-thiazin-4-one structures of the methyl derivative as well as 1-(9-acridinyl)thiosemicarbazide available from X-ray crystallographic analysis. Tactics utilizing spectroscopic methods {1R frequencies (nu) and NMR chemical shifts (delta), scalar coupling constants (J), and NOEs (eta)} in conjunction with molecular modeling calculations of the spectral parameters (frequency calculations (v) and NMR 6 using the GIAO method and J by calculation of the Fermi contact term) were evaluated in terms of proving 5- or 6-membered ring formation.},
  language  = {en}
}
@article{BalciKochKleinpeter2006,
  author    = {Balci, Kubilay and Koch, Andreas and Kleinpeter, Erich},
  title     = {A comparative vibrational spectroscopic investigation of free mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers based on DFT calculations},
  issn      = {0022-2860},
  doi       = {10.1016/j.molstruc.2005.10.048},
  year      = {2006},
  abstract  = {A successful assignment for the fundamental bands observed in the experimental IR spectra of mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers was achieved by the aid of the density functional theory (DFT) based quantum mechanical calculations carried out at the 133LYP/6-31G(d) and B3LYP/6-31 + G(d) level of theory. Two different scaling approaches, '(i) scaled quantum mechanics force field (SQM FF) methodology', and (ii) the 'scaling frequencies with dual empirical scale factors', were used in order to fit the calculated harmonic frequencies to the experimental ones. Potential energy distribution (PED) calculations were carried out to define the internal coordinate contributions to each normal mode and to define the corresponding normal modes of the molecules. The effects of the conformational differences onto the IR active normal modes of the two isomeric molecules and their corresponding experimental frequencies were discussed in the light of the calculated spectral data.},
  language  = {en}
}
@article{ShainyanUshakovKochetal.2006,
  author    = {Shainyan, Bagrat A. and Ushakov, Igor A. and Koch, Andreas and Kleinpeter, Erich},
  title     = {Stereodynamics of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane: Experimental and theoretical analysis},
  doi       = {10.1021/Jo061112x},
  year      = {2006},
  abstract  = {Dynamic NMR of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane reveals the existence of three conformers and two dynamic processes: ring inversion and rotation about the N-S bond, both processes having Delta G(double dagger) = 13.5 kcal/mol. An unprecedented large reverse Perlin effect (J(CHax) > J(CHeq)) was found experimentally and calculated theoretically.},
  language  = {en}
}
@article{KleinpeterBoelkeKoch2010,
  author    = {Kleinpeter, Erich and Boelke, Ute and Koch, Andreas},
  title     = {Subtle Trade-off Existing between (Anti)Aromaticity, Push-Pull Interaction, Keto-Enol Tautomerism, and Steric Hindrance When Defining the Electronic Properties of Conjugated Structures},
  issn      = {1089-5639},
  year      = {2010},
  language  = {en}
}
@article{KleinpeterKoch2010,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Identification of benzenoid and quinonoid structures by through-space NMR shieldings (TSNMRS)},
  issn      = {1089-5639},
  year      = {2010},
  language  = {en}
}
@article{KleinpeterKoch2010,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Probing the exohedral magnetic properties of C20 derivatives by through space NMR shieldings (TSNMRS)},
  issn      = {0166-1280},
  doi       = {10.1016/j.theochem.2009.09.018},
  year      = {2010},
  abstract  = {The through space NMR shieldings (TSNMRS) of dodecahedrane C20H20, of the isomeric hydrocarbons C20H12, of the ions C20H122+ and C20H122- of the fluxional fullerene C20 and of its dication C202+ have been ab initio calculated employing the NICS concept on basis of MP2/6-31G* geometries and visualized as iso-chemical-shielding/deshielding surfaces (ICSSs). TSNMRS values were employed to study the exohedral magnetic properties of the compounds studied. Hereby, the curved It-conjugation in the compounds studied could be quantified.},
  language  = {en}
}
@article{KleinpeterKlodKoch2007,
  author    = {Kleinpeter, Erich and Klod, Sabrina and Koch, Andreas},
  title     = {Visualization of through space NMR shieldings of aromatic and anti-aromatic molecules and a simple means to compare and estimate aromaticity},
  issn      = {0166-1280},
  doi       = {10.1016/j.theochem.2007.02.049},
  year      = {2007},
  abstract  = {Through space NMR shieldings of aromatic (benzene, mono-substituted and annelated benzenes, ferrocene, [14]- and [18]-annulenes, phenylenes and tetra- to heptahelicene) and anti-aromatic molecules (cyclobutadiene and pentalene) were assessed by ab initio molecular-orbital calculations. Employing the nucleus-independent chemical shifts (NICS) concept, these through space NMR shieldings were visualized as iso-chemical-shielding surfaces (ICSSs) and can be applied quantitatively to determine the stereochemistry of proximal nuclei. In addition, the distances in {\AA} at ICSS values of ±0.1 ppm in-plane and perpendicular-to-center of the aromatic ring system were employed as a simple means to compare and estimate qualitatively the aromaticity of the systems at hand.},
  language  = {en}
}
@article{KleinpeterKoch2009,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {Visualization of homoaromaticity in cations, neutral molecules and anions by spatial magnetic properties (through space NMR shieldings) - an 1H/13C NMR chemical shift study},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2009.04.063},
  year      = {2009},
  abstract  = {Prototypes for homoaromaticity in cations, neutral molecules, and anions are theoretically studied at the MP2 level of theory. For the global minimum structures on the potential energy surface both 1H/13C chemical shifts and spatial magnetic properties as through space NMR shieldings (TSNMRS) were calculated by the GIAO perturbation method. The TSNMRS are visualized as iso-chemical-shielding surfaces (ICSS) of different sign and size. Coincident experimental and computed 1H/13C chemical shifts afforded the possibility to decide from the TSNMRSs at hand on both the existence and the size of homoaromaticity in the molecules studied.},
  language  = {en}
}
@article{ThothSzatmariHeydenreichetal.2009,
  author    = {Th{\´o}th, Di{\´a}na and Szatm{\´a}ri, Istv{\´a}n and Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Fulop, Ferenc},
  title     = {Synthesis and conformational analysis of naphthylnaphthoxazine derivatives},
  issn      = {0166-1280},
  doi       = {10.1016/j.molstruc.2009.04.015},
  year      = {2009},
  abstract  = {Four new primary aminonaphthols (4, 5, 9 and 10) were synthesized from 1- or 2-naphthol and 1- or 2- naphthaldehyde via naphthoxazines in modified Mannich condensations. Simple ring-closure reactions of these aminonaphthols with paraformaldehyde, 4-nitrobenzaldehyde, phosgene or 4-chlorophenyl isothiocyanate led to new heterocyclic derivatives. In these transformations, either an sp2 or an sp3 carbon was inserted between the hydroxy and amino groups. The effects of substituents and the naphthyl ring on the conformation were investigated by means of NMR measurements, employing both dipolar and scalar couplings. The structures were confirmed by DFT quantum chemical calculations involving computed coupling constants, intramolecular distances between nuclei and the relative energies of the preferred conformers.},
  language  = {en}
}
@article{BalciKochKleinpeter2009,
  author    = {Balci, Kubilay and Koch, Andreas and Kleinpeter, Erich},
  title     = {A theoretical IR spectroscopic study based on DFT calculations for free mn-15S(2)O(3) maleonitrile-dithiacrown ether compound},
  issn      = {0022-2860},
  doi       = {10.1016/j.molstruc.2008.08.027},
  year      = {2009},
  abstract  = {The theoretically possible stable conformers of free mn-15S2O3 maleonitrile-dithiacrown ether molecule were searched by means of a conformational study which consists of molecular dynamics and energy minimization calculations performed with MM2 force field and successive geometry optimization + frequency calculations performed first at B3LYP/3- 21G and then at B3LYP/6-31G(d) levels of theory. The obtained calculation results have clearly indicated that the free molecule in electronic ground state is very flexible and accordingly has many possible stable conformers of different conformational properties at room temperature; among them, the one having a macrocyclic ring structure in which all of the ether units oriented toward the center of the ring was determined the energetically most preferable conformer. In addition, the equilibrium geometrical parameters, vibrational normal modes and associated IR spectral data of the determined most stable three conformers of the molecule were calculated at B3LYP/6-31+G(d) and B3LYP/6-31++G(d,p) levels of theory. A successful assignment of the fundamental bands observed in the recorded experimental solid phase and solution phase IR spectra of the molecule was achieved in the light of the theoretical data obtained from these DFT calculations. To fit the calculated harmonic wavenumbers to the experimental ones, two different scaling procedures, referred to as "Scaled Quantum Mechanical Force Field (SQM FF) methodology" and "Scaling wavenumbers with empirical dual scale factors", were proceeded independently.},
  language  = {en}
}
@article{KleinpeterKoch2009,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {pi-delocalization in oligoalkynes induced by push-pull substituents and 1,3-conjugation : a combined 13C NMR and computational study ; dedicated to Prof. Alan R. Katritzky},
  issn      = {1089-5639},
  doi       = {10.1021/Jp905873f},
  year      = {2009},
  abstract  = {13C chemical shifts of the push;pull oligoalkynes Don-(C;C)n-Acc (n = 1;4; Don = morpholino; Acc = COMe, COOMe) were computed at the DFT (B3LYP/6-311+G(d,p) level of theory compared with the experimental ; values and the agreement employed as a measure of quality for the underlying structures. For the global minima structures, the occupation quotients of antibonding ;* and bonding ; orbitals (;*C;C/ ;C;C) and the bond lengths (dC;C) of the various C;C triple bonds were also computed and correlated to each other. The linear dependence obtained for the two parameters dC;C and ;*C;C/ ;C;C quantifies changes in ;-delocalization induced by the push;pull effect of the substituents and 1,3-conjugation (1,3,5- and 1,3,5,7-, respectively) of the C;C bonds in the oligoalkynes studied. A critical comparison of the push;pull effect, attenuated with increasing n, and the conjugative stabilization of the oligoalkynes, increasing with n, as concluded from dC;C and ;*C;C/;C;C of the oligoalkynes and the reference compounds Me-(C;C)n-Me, Don-(C;C)n-Me, and Me-(C;C)n-Acc), respectively (Don = morpholino; Acc = COMe, COOMe), is affiliated.},
  language  = {en}
}
@article{SzatmariTothKochetal.2006,
  author    = {Szatmari, Istvan and Toth, Diana and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc},
  title     = {Study of the substituent-influenced anomeric effect in the ring-chain tautomerism of 1-alkyl-3-aryl-naphth[1,2- e][1,3]oxazines},
  doi       = {10.1002/ejoc.200600563},
  year      = {2006},
  abstract  = {The stabilities of the trans (B) and cis (C) tautomeric ring forms that are experimentally observed in the ring- chain tautomeric interconversion of 1-alkyl-3-aryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines has been investigated. Stability differences are explained by the analysis of the natural bond orbital results for the lone pairs of electrons that are on the heteroatoms in the oxazine ring system and by regression analysis of the calculated 13C NMR chemical shift values.},
  language  = {en}
}
@article{SarodnickLinkerHeydenreichetal.2009,
  author    = {Sarodnick, Gerhard and Linker, Torsten and Heydenreich, Matthias and Koch, Andreas and Starke, Ines and F{\"u}rstenberg, Sylvia and Kleinpeter, Erich},
  title     = {Quinoxalines XV : convenient synthesis and structural study of pyrazolo[1,5-alpha]quinoxalines},
  issn      = {0022-3263},
  doi       = {10.1021/Jo802398g},
  year      = {2009},
  abstract  = {A series of aryloxymethylquinoxaline oximes, hitherto unknown and synthesized from the corresponding aldehydes, afforded in only one step pyrazolo[1,5-;]quinoxalines in the presence of acetic anhydride at high temperatures. A formal [3,5]-sigmatropic rearrangement was proposed as the mechanistic rationale for this unprecedented transformation. Saponification with potassium hydroxide furnished the free phenol derivatives which were studied by NMR spectroscopy and accompanying theoretical DFT calculations, establishing intramolecular hydrogen bonding and the spatial magnetic properties. Additionally, mass spectrometric fragmentation was investigated by B/E-linked scans and collision-induced dissociation experiments. The fragmentation pattern devoted a new gas phase rearrangement process, which proved to be unique and characteristic for pyrazolo[1,5-;]quinoxalines.},
  language  = {en}
}
@article{BoehmTomaszcikovaImrichetal.2009,
  author    = {B{\"o}hm, Stanislav and Tomaszcikov{\´a}, Jana and Imrich, J{\´a}n and Danihel, Ivan and Kristian, Pavol and Koch, Andreas and Kleinpeter, Erich and Klika, Karel D.},
  title     = {Computational study to assign structure, tautomerism, E/Z and s-cis/s-trans isomerism, pi-delocalization, partial aromaticity, and the ring size of 1,3-thiazolidin-4-ones and 1,3-thiazin-4-ones formed from thiosemicarbazides},
  issn      = {0166-1280},
  year      = {2009},
  abstract  = {A set of structures encompassing 1-(9-acridinyl)thiosemicarbazide and its 2-methyl derivative together with their various tautomeric structures; the 5-membered ring 1,3-thiazolidin-4-one products resulting from the reaction of 1- (9-acridinyl)thiosemicarbazide and its 2-methyl derivative with dimethyl acetylenedicarboxylate (DMAD) together with the alternative 6-membered ring isomeric reaction products as well as other potential isomeric structures; and the 6- membered ring 1,3-thiazin-4-one product resulting from the reaction of 2-methyl-1-(9-acridinyl)thiosemicarbazide with methyl propiolate (MP) together with the alternative 5-membered ring isomeric reaction product were all extensively studied by molecular modeling calculations using DFT at the B3LYP/6-31G(d,p) level of theory. The ring-chain tautomerism of the thiosemicarbazides, the regio- and stereoselectivity of the reactions, the adopted conformations and E/Z configurations of the products, the prototropic tautomerism of all the compounds, and the reasons for the predominance of the s-cis conformation of the Z configuration of the 1,3-thiazolidin-4-one product in particular were all extensively analyzed. Comparison of the modeled structures were also made to the 1,3-thiazolidin-4-one and 1,3-thiazin-4-one structures of the methyl derivative as well as 1-(9-acridinyl)thiosemicarbazide available from X-ray crystallographic analysis. Tactics utilizing spectroscopic methods {IR frequencies (;) and NMR chemical shifts (;), scalar coupling constants (J), and NOEs (;)} in conjunction with molecular modeling calculations of the spectral parameters {frequency calculations (;) and NMR ; using the GIAO method and J by calculation of the Fermi contact term} were evaluated in terms of proving 5- or 6-membered ring formation.},
  language  = {en}
}
@article{KleinpeterSzatmariLazaretal.2009,
  author    = {Kleinpeter, Erich and Szatm{\´a}ri, Istv{\´a}n and L{\´a}z{\´a}r, L{\´a}szl{\´o} and Koch, Andreas and Heydenreich, Matthias and Fulop, Ferenc},
  title     = {Visualization and quantification of anisotropic effects on the 1H NMR spectra of 1,3-oxazino[4,3- alpha]isoquinolines - indirect estimates of steric compression},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2009.07.038},
  year      = {2009},
  abstract  = {The anisotropic effects of the phenyl, alpha- and beta-naphthyl moieties in four series of 1,3-oxazino[4,3- a]isoquinolines on the H-1 chemical shifts of the isoquinoline protons were calculated by employing the Nucleus Independent Chemical Shift (NICS) concept and Visualized as anisotropic cones by a through-space NMR shielding grid. The signs and extents of these spatial effects on the H-1 chemical shifts of the isoquinoline protons were compared with the experimental H-1 NMR spectra. The differences between the experimental delta (H-1)/ppm values and the calculated anisotropic effects of the aromatic moieties are discussed in terms of the steric compression that occurs in the Compounds studied.},
  language  = {en}
}
@article{StarkeKochUhlemannetal.1995,
  author    = {Starke, Ines and Koch, Andreas and Uhlemann, Erhard and Kleinpeter, Erich},
  title     = {Nuclear-magnetic-resonance studies and molecular modelling of the solution structure of some dibenzo crown- ethers and their complexes},
  year      = {1995},
  language  = {en}
}
@article{StarkeKochHoldtetal.1995,
  author    = {Starke, Ines and Koch, Andreas and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich},
  title     = {1H, 13C, and 15N NMR study of the solution structure of metabridged bis(benzo-15-crown-5-ether)s},
  year      = {1995},
  language  = {en}
}
@article{KleinpeterKochHeydenreichetal.1995,
  author    = {Kleinpeter, Erich and Koch, Andreas and Heydenreich, Matthias and Chatterjee, S. K. and Rudorf, Wolf-Dieter},
  title     = {Study of the pi-electron distribution in push-pull alkenes by 1H and 13C NMR spectroscopy, IV : the conformation and dynamic behaviour of substituted N-Phenyl-2,3-dihydro-4(1H)-pyridones},
  year      = {1995},
  language  = {en}
}
@article{KochStarkeKleinpeter1995,
  author    = {Koch, Andreas and Starke, Ines and Kleinpeter, Erich},
  title     = {Conformational study of Dibenzo crown ethers and their complexation with Li+ and Na+},
  year      = {1995},
  language  = {en}
}
@article{KochKleinpeter1995,
  author    = {Koch, Andreas and Kleinpeter, Erich},
  title     = {Ab-initio study and semiempirical calculations of keto-enol tautomerism of triazolopyrimidines},
  year      = {1995},
  language  = {en}
}
@article{KleinpeterHeydenreichKalderetal.1997,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Kalder, L. and Koch, Andreas and Henning, Dietrich and Kempter, Gerhard and Benassi, Rois and Taddei, F.},
  title     = {NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution},
  year      = {1997},
  language  = {en}
}
@article{KochKleinpeter1997,
  author    = {Koch, Andreas and Kleinpeter, Erich},
  title     = {Study of the tautomerism by experimentally and theoretically estimated 13C and 15N chemical shifts},
  year      = {1997},
  language  = {en}
}
@article{HeydenreichKochKleinpeteretal.1997,
  author    = {Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Zimmermann, Thomas},
  title     = {Dynamic NMR study of the flexibility of 2-amino-3-aroyl-4,6-diaryl-pyrylium salts},
  issn      = {0937-0633},
  doi       = {10.1007/s002160050205},
  year      = {1997},
  language  = {en}
}
@article{KochKleinpeter1997,
  author    = {Koch, Andreas and Kleinpeter, Erich},
  title     = {Restricted rotation about particial C, N Double Bond},
  year      = {1997},
  language  = {en}
}
@article{KleinpeterKochFischeretal.1997,
  author    = {Kleinpeter, Erich and Koch, Andreas and Fischer, G. and Askolin, C.-P.},
  title     = {13 C NMR, 15 N NMR and quantum-chemical study of the tautomerism of 2-substituted 5-ME-7-OH-1,2,4-triazolo[1,5- a]pyrimidines},
  year      = {1997},
  language  = {en}
}
@article{KalliesKochMitzner1997,
  author    = {Kallies, Bernd and Koch, Andreas and Mitzner, Rolf},
  title     = {Competitive resonance at the carbonyl group as visualized by the natural bond orbital analysis},
  year      = {1997},
  language  = {en}
}
@article{KleinpeterHeydenreichKalderetal.1997,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Kalder, L. and Koch, Andreas and Henning, Dietrich and Kempter, Gerhard},
  title     = {NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution},
  year      = {1997},
  language  = {en}
}
@article{KochThomasKleinpeter1997,
  author    = {Koch, Andreas and Thomas, Steffen and Kleinpeter, Erich},
  title     = {Ab-initio study, semi-empirical calculation and NMR spectroscopy of keto-enol tautomerism of triazolopyrimidines},
  year      = {1997},
  language  = {en}
}