Abstract

Neda Samiei Soofi and Majid Monajjemi

DOI : http://dx.doi.org/10.13005/ojc/320504

There are no theoretical or mathematical reports of a statistical approach in NMR shielding and nucleus independent chemical shifts, while the asymmetry (η) and skew (κ) parameters are fluctuated in short distances and are alternative in long distances. In the case of axially symmetric tensor, σ₂₂ equals either σ₁₁ or σ₃₃, skew is κ= ±1 and by changing asymmetry between 0 ≤ η ≤ +1 skew will be changed between -1 ≤ κ ≤ +1 , meanwhile the parameter “κ” is zero when σ₂₂ = σ_iso. In this work, we have investigated a statistical method by computing of Nucleus-Independent Chemical Shifts (S-NICS) in point of probes motions in a sphere of shielding and deshielding spaces of SiO₂ rings. Monajjemi in the previous work [24], has  investigated a new method as the name “ S-NICS” which this method is  suitable for calculation the aromaticity in the non-benzene rings such as SiO₂ rings which is a famous catalyst for organic chemical synthesize and reaction. Although S-NICS values for some molecules such as benzene, borazine and naphthalene can be indicated as the aromaticity criterion, for other cases such as B_nN_nH_x and their hydrogenated derivatives, these values indicate electromagnetic index. Finally, we have introduced a schematic diagram of statistical-nucleus independent chemical shifts for ab-initio calculations in Gaussian program, Games or other software.

naphthalene; electromagnetic index; NMR shielding

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