@article{KochStamboliyskaMikhovaetal.2019,
  author    = {Koch, Andreas and Stamboliyska, Bistra and Mikhova, Bozhana and Breznica-Selmani, Pranvera and Mladenovska, Kristina and Popovski, Emil},
  title     = {Calculations of C-13 NMR chemical shifts and F-C coupling constants of ciprofloxacin},
  series = {Magnetic resonance in chemistry},
  volume    = {57},
  journal   = {Magnetic resonance in chemistry},
  number    = {4},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0749-1581},
  doi       = {10.1002/mrc.4827},
  pages     = {75 -- 84},
  year      = {2019},
  abstract  = {Ciprofloxacin is a widely used fluoroquinolone antibiotic. In this work, a comprehensive evaluation of MP2 and DFT with different functionals and basis sets was carried out to select the most suitable level of theory for the study of the NMR properties of ciprofloxacin. Their relative predictive capabilities were evaluated comparing the theoretically predicted and experimental spectral data. Our computational results indicated that in contrast to the solid state, the molecule of ciprofloxacin does not exist as a zwitterion in gaseous state. The results of the calculations of the chemical shifts most close to the experimental were obtained with B3LYP/aug-cc-pVDZ. The F-C coupling constants were calculated systematically with different DFT methods and several basis sets. In general, the calculations of the coupling constants with the BHandH computational method including the applied in this work 6-311++G**, EPRII, and EPRIII basis sets showed a good reproducibility of the experimental values of the coupling constants.},
  language  = {en}
}
@article{KleinpeterStamboliyska2009,
  author    = {Kleinpeter, Erich and Stamboliyska, Bistra A.},
  title     = {Hyperpolarizability of donor-acceptor azines subject to push-pull character and steric hindrance},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2009.09.026},
  year      = {2009},
  abstract  = {The push-pull character of two series of donor-acceptor azines has been quantified by C-13, N-15 chemical shift differences of the partial C(1)=N(1) and N(2)=C(2) double bonds in the central linking C(1)=N(1)-N(2)=C(2) unit and by the quotient of the occupations of the bonding pi and anti-bonding pi* orbitals of these bonds. Excellent correlation of the latter push-pull parameter with the corresponding bond lengths d(C=N) strongly recommend both the occupation quotients pi*/pi and the corresponding bond lengths as reasonable sensors for quantifying the push, pull character along the C=N-N=C linking unit, for the donor-acceptor quality of the two series of azines and for the molecular hyperpolarizability beta(0) of these compounds. Within this context, reasonable conclusions concerning the interplay of steric hindrance in the chromophore, push-pull character and hyperpolarizability of the azines and their application as NLO materials will be drawn.},
  language  = {en}
}
@article{KleinpeterStamboliyska2008,
  author    = {Kleinpeter, Erich and Stamboliyska, Bistra A.},
  title     = {Quantification of the Push-Pull Character of Donor-Acceptor Triazenes},
  doi       = {10.1021/Jo8013758},
  year      = {2008},
  abstract  = {The Push-pull character of two series of donor-acceptor triazenes has been quantified by C-13 and N-15 chemical shift differences of the partial N(1)=N(2) and N(3)=C(4) double bonds in the central linking C=N-N=N-C unit and by the quotient of the occupations of both the bonding pi and antibonding orbitals pi* of these partial double bonds. Excellent correlations of the two estimates, to quantify the push-pull effect, with the bond lengths strongly recommend the occupation quotients pi*/pi, the N-15 chemical shift differences Delta delta[N(l),N(2)], and the corresponding bond lengths as reasonable sensors for quantifying charge alternation along the C=N-N=N-C linking unit, for the donor- acceptor quality of the triazenes 1 and 2 and for the molecular hyperpolarizability beta(0) of these compounds. Within this context, certain Substances can be strongly recommended for NLO application.},
  language  = {en}
}
@article{KleinpeterKochMikhovaetal.2008,
  author    = {Kleinpeter, Erich and Koch, Andreas and Mikhova, Bozhana and Stamboliyska, Bistra A. and Kolev, Tsonko M.},
  title     = {Quantification of the push-pull character of the isophorone chromophore as a measure of molecular hyperpolarizability for NLO applications},
  issn      = {0040-4039},
  doi       = {10.1016/j.tetlet.2007.12.107},
  year      = {2008},
  abstract  = {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.},
  language  = {en}
}