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Which NICS Aromaticity Index for Planar π Rings Is Best?

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journal contribution
posted on 02.03.2006 by Hossein Fallah-Bagher-Shaidaei, Chaitanya S. Wannere, Clémence Corminboeuf, Ralph Puchta, Paul v. R. Schleyer
Five increasingly sophisticated aromaticity indexes, based on nucleus-independent chemical shifts (NICS), were evaluated against a uniform set of aromatic stabilization energies (ASE) for 75 mono- and polyheterocyclic five-membered rings. While acceptable statistical correlations were given by all of the NICS methods, the most fundamentally grounded index, NICS(0)πzz (based on the π contribution to the out-of-plane zz tensor component), performed best statistically (cc = 0.980) and in practice. The easily computable NICS(1)zz index is a useful alternative (cc = 0.968).