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

Autor: Hamid Saeidian, Zohreh Mirjafary, Maryam KamalZade Gilani
Rok vydání: 2020
Předmět:
Zdroj: Structural Chemistry. 31:1545-1551
ISSN: 1572-9001
1040-0400
DOI: 10.1007/s11224-020-01520-0
Popis: 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.
Databáze: OpenAIRE
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