Aromaticity of ionic structures: Investigation and application of nics value and 4n = 2 rule

Abstract

At DFT/B3LYP/6-31G** theoretical level, C 6H 6 N and C 6 n (n = 0, ±2, and =2), C 6H 6 n and C 6 n (n = 0, =2, ±4, and ±6), C 6Hn n=6 (n = 0-6), as well as C 6H 6-A and C 6-A (A = Be, B, N, O, Mg, Al, Si, S, and Fe) structures were investigated. Comparing NICS values of C 6H 6 n and C 6 n (n = 0, ±2, and +2), we discovered that C 6H 6-2l ,C 6H 6+2 were antiaromatic, and C 6H 6,C 6,C 6-2 ,C 6+2 had aromaticity with negative NICS values. According to research of C 6H 6 n and C 6 n (n = 0, ±2, ±4, ±6), C 6Hn n -6 (n = 0-6), we sustained that their & and π orbit were different and the locations of electrons were dif?cult to con?rm in ionic structures. Thus, neither 4n + 2 rule nor NICS values can precisely estimate the aromaticity of ionic structures. Besides, through WBI (NBO) research of C 6H 6-A and C 6-A (A = Be, B, N, O, Mg, Al, Si, S, and Fe) structures, e found that C 6H 6 was easy to accept electrons, contrarily, C 6 was prone to bestowing electrons. Moreover, C 6H 6 took the symmetrical carbon atoms form feeble interaction or bond, and C 6 used all carbon atoms to impact with other atom. C 6H 6 generated two contrapuntal single bonds with oxygen, sulfur, and nitrogen atoms, whereas C 6 molecule formed double bond with oxygen and nitrogen atoms, two conjoint single bonds with sulfur atom. © 2009 Wiley Periodicals, Inc 2010.