Halogen effect on structure and 13C NMR chemical shift of 3,6-disubstituted-N-alkyl carbazoles

Klaudia Radula-Janik, Teobald Kupka, Krzysztof Ejsmont, Zdzislaw Daszkiewicz, Stephan P. A. Sauer

22 Citationer (Scopus)

Abstract

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 13C 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.

OriginalsprogEngelsk
TidsskriftMagnetic Resonance in Chemistry
Vol/bind51
Udgave nummer10
Sider (fra-til)630-635
Antal sider6
ISSN0749-1581
DOI
StatusUdgivet - okt. 2013

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  • Det Natur- og Biovidenskabelige Fakultet

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