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Halogen effect on structure and 13 C NMR chemical shift of 3,6‐disubstituted‐ N ‐alkyl carbazoles
Author(s) -
RadulaJanik Klaudia,
Kupka Teobald,
Ejsmont Krzysztof,
Daszkiewicz Zdzislaw,
Sauer Stephan P. A.
Publication year - 2013
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.3992
Subject(s) - chemistry , halogen , chemical shift , electronegativity , substituent , alkyl , density functional theory , carbon 13 nmr , computational chemistry , atom (system on chip) , crystallography , medicinal chemistry , stereochemistry , organic chemistry , computer science , embedded system
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 13 C 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 ~−30 ppm 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 © 2013 John Wiley & Sons, Ltd.