TY  - JOUR
A1  - Koch, Andreas
A1  - Stamboliyska, Bistra
A1  - Mikhova, Bozhana
A1  - Breznica-Selmani, Pranvera
A1  - Mladenovska, Kristina
A1  - Popovski, Emil
T1  - Calculations of C-13 NMR chemical shifts and F-C coupling constants of ciprofloxacin
JF  - Magnetic resonance in chemistry
N2  - 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.
KW  - C-13 chemical shifts
KW  - ciprofloxacin
KW  - DFT calculations
KW  - F-C coupling constants
KW  - NMR
Y1  - 2019
U6  - https://doi.org/10.1002/mrc.4827
SN  - 0749-1581
SN  - 1097-458X
VL  - 57
IS  - 4
SP  - 75
EP  - 84
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stamboliyska, Bistra A.
T1  - Hyperpolarizability of donor-acceptor azines subject to push-pull character and steric hindrance
N2  - 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.
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2009.09.026
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stamboliyska, Bistra A.
T1  - Quantification of the Push-Pull Character of Donor-Acceptor Triazenes
N2  - 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.
Y1  - 2008
UR  - http://pubs.acs.org/doi/full/10.1021/jo8013758
U6  - https://doi.org/10.1021/Jo8013758
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  -