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Absolute magnetic shielding

Nuclear-independent chemical shift (NICS) is the negative value of absolute magnetic shielding calculated at revealing points in or near an aromatic system. Rings with negative NICS and NICS(l) values computed at the center... [Pg.442]

One of the well-accepted magnetic criteria of aromaticity is the nucleus independent chemical shift (NICS) which is defined as the negative value of the absolute magnetic shielding calculated at some selective points. The NICS(O) and NICS(l) values are computed at the centre and lA above the aromatic ring respectively. Aromatic systems possess negative NICS values as that indicates the presence of an induced diatropic ring current. Positive NICS values refer to paratropicity and are present in antiaromatic... [Pg.51]

Nucleus-independent chemical shifts (NICS) provide a useful criterion of aromaticity/antiaromaticity. Absolute magnetic shieldings are computed at ring centers (nonweighted mean of the heavy atom coordinates) and correspond to the NMR chemical shift convention the signs are reversed, so that negative NICS values denote aromaticity and positive NICS values denote antiaromaticity. [Pg.3]

Wasylishen, R. E. and Bryce, D. L. (2002). A revised experimental absolute magnetic shielding scale for oxygen. J. Chem. Phys., 117, 10061. [Pg.295]

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See also in sourсe #XX -- [ Pg.151 ]



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