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  - Koch, Andreas
A1  - Mikhova, Bozhana
A1  - Kleinpeter, Erich
T1  - Ab initio MP2/GIAO/NBO study of the delta-syn-axial effect in C-13 NMR spectroscopy
N2  - The C-13 chemical shifts of 20 rigid bicyclic compounds have been calculated with ab initio HF and MP2 methods. The calculations showed very good reproducibility of the experimental values. The molecular orbital interactions in the rigid, nearly planar delta-syn-axial fragments in the isomeric groups of norbornane derivatives 1.x-4.x were studied in detail and were employed to explain the deshielding delta-syn-axial effect in C-13 NMR spectroscopy. (C) 2004 Elsevier B.V. All rights reserved
Y1  - 2004
SN  - 0022-2860
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  -