Aromaticity of N-heterocyclic carbene and its analogues: Magnetically induced ring current perspective |
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Authors: | Shanti G. Patra Nilangshu Mandal |
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Affiliation: | 1. Department of Chemical Sciences, Ariel University, Ariel, Israel;2. School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, India |
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Abstract: | The N-heterocyclic carbene, imidazole-2-ylidene, and its main group (13-15) analogues contain cyclically conjugated 6π electrons. Experimental 1H nuclear magnetic resonance (NMR) spectra suggest an increase in aromaticity along a period from left to right. Whereas the order along a group is as follows: period 2 > period 5 > period 4 > period 3 due to change in structure. To understand the order of aromaticity, the magnetically induced ring currents of the molecules are calculated using aromatic ring current shielding, gauge-including magnetically induced currents (GIMIC) method and Stanger's σ-model applying the gauge-including atomic orbitals NMR technique. It is found that GIMIC best describes the order of aromaticity especially along a group where current-profile changes on the bivalent atom down a group due to change in electron density. Moreover, the GIMIC provides the visualization of current by sign modulus and the anisotropy of the induced current density plots. |
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Keywords: | ACID aromaticity GIMIC NICS ring current |
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