Relation between the substituent effect and aromaticity in imidazole derivatives: A comparative study

• Published in: Computational and theoretical chemistry Vol. 994; pp. 97 - 104
• Main Authors: Chermahini, Alireza Najafi, Hosseinzadeh, Behzad, Beni, Alireza Salimi, Teimouri, Abbas
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2012
• Subjects: HOMA; Imidazolate; Imidazole; NBO; NICS; Protonated imidazole; Imidazolate; Protonated imidazole; NBO; HOMA; Imidazole; NICS
• ISSN: 2210-271X
• DOI: 10.1016/j.comptc.2012.06.024

Relation between the substituent effect and aromaticity in imidazole derivatives: a comparative study. [Display omitted] ► The aromaticity character of imidazole derivatives at 2, 4 and 5 positions calculated using various methods. ► The effect of substituent on aromaticity investigated. ► The aromaticities were compared with each other. ► The aromaticity character of imidazolate anions and imidazolium cations calculated and compared. The energies and aromaticity of a series of R substituted imidazoles [R=NH2, OH, H, CH3, F, Cl, CN, NO, NO2], their anions and protonated forms in the gas phase have been calculated with the DFT/B3LYP and MP2 methods at the 6-311++G(d,p) level. We have analyzed the change of local aromaticity using several aromaticity indicators (Pozharsky Index, HOMA, NICS, ASE and pEDA) and found a considerable ring aromaticity for imidazoles, imidazolate anions and their protonated forms. In each class anion forms have the most aromaticity and in neutral forms, 1-H imidazoles have less aromaticity character. The HOMA and structural AI show good correlation with each other but NICS (0) values showed a poor correlation with other scales. The geometrical indices seem to be better correlate with substituent effect.