Journal
MAGNETIC RESONANCE IN CHEMISTRY
Volume 51, Issue 10, Pages 630-635Publisher
WILEY
DOI: 10.1002/mrc.3992
Keywords
carbazole; C-13 NMR; GIAO NMR; halogen substituent; relativistic effect; HALA
Funding
- Faculty of Chemistry, University of Opole [8/WCH/2013-S]
- European Social Fund 'Uniwersytecki Program Stypendialny'
- Supercomputing and Networking Center ACK CYFRONET AGH in Krakow [MNiSW/SGI3700/UOpolski/061/2008]
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Structures of selected 3,6-dihalogeno-N-alkyl carbazole derivatives were calculated at the B3LYP/6-311++G(3df,2pd) level of theory, and their C-13 nuclear magnetic resonance (NMR) isotropic shieldings were predicted using density functional theory (DFT). The model compounds contained 9H, N-methyl and N-ethyl derivatives. The relativistic effect of Br and I atoms on nuclear shieldings was modeled using the spin-orbit zeroth-order regular approximation (ZORA) method. Significant heavy atom shielding effects for the carbon atom directly bonded with Br and I were observed ( -10 and -30ppm while the other carbon shifts were practically unaffected). The decreasing electronegativity of the halogen substituent (F, Cl, Br, and I) was reflected in both nonrelativistic and relativistic NMR results as decreased values of chemical shifts of carbon atoms attached to halogen (C3 and C6) leading to a strong sensitivity to halogen atom type at 3 and 6 positions of the carbazole ring. The predicted NMR data correctly reproduce the available experimental data for unsubstituted N-alkylcarbazoles. Copyright (c) 2013 John Wiley & Sons, Ltd.
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