Harnessing aromaticity and intramolecular hydrogen bonding to tailor organosuperbases by using 2,4,6-cycloheptatriene-1-imine scaffold

被引:0
作者
Maryam Gilani
Hamid Saeidian
Zohreh Mirjafary
机构
[1] Islamic Azad University,Department of Chemistry, Science and Research Branch
[2] Payame Noor University (PNU),Department of Science
来源
Structural Chemistry | 2020年 / 31卷
关键词
DFT calculations; Cycloheptatriene-1-imine; Organosuperbase; Aromaticity index; Intramolecular hydrogen bonding; Proton affinity;
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摘要
The density functional theory (DFT) calculations at B3LYP/6-31 + G(d,p) level were performed for a series of new 2,4,6-cycloheptatriene-1-imine scaffolds which have potential to introduce as organosuperbases. In the present study, we have exploited the 2,4,6-cycloheptatriene-1-imines which strategically substituted at 2 and 7 positions by two potential anchoring arms having lone pair possessing atoms. The designed organic superbases were found to have the higher basicity than the benchmarked molecule, 1,8-bis(dimethylamino)-naphthalene. The proposed superbase B14 bearing guanidine and aniline groups possesses the highest proton affinity value as 1143.8 kJ mol−1. The protonation enthalpy, Gibbs free energy, harmonic oscillator model of aromaticity (HOMA), and nucleus-independent chemical shift (NICS) were used for the basicity comparison. After the protonation of the designed molecules, the positive charge on the conjugate acid is expected to be delocalized in the cycloheptatriene ring and led to its aromatization. The results indicate that the HOMA and NICS values of the ring in the conjugate acid are strongly elevated. On the other hand, very strong intramolecular hydrogen bonding is formed after protonation. These two factors enhance the stability of the conjugate acids and thereby increase the basicity of the designed molecules.
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页码:1545 / 1551
页数:6
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