Studies of the Functionalized α-Hydroxy-<i>p</i>-Quinone Imine Derivatives Stabilized by Intramolecular Hydrogen Bond

Abstract

In this work, reactions between 6,7-dichloropyrido[1,2-a]benzimidazole-8,9-diones with different benzohydrazides were studied. Nucleophilic substitution at C(6) was followed by isomerization and led to α-hydroxy-p-quinone imine derivatives. Synthesized compounds represent a combination of several structural motifs: a benzimidazole core fused with α-hydroxy-p-quinone imine, which contains a benzamide fragment. X-ray crystallography analysis revealed the formation of dimers linked through OH···O interactions and stabilization of the imine form by strong intramolecular NH···N hydrogen bonds. The protonation/deprotonation processes were investigated in a solution using UV–Vis spectroscopy and a 1H NMR titration experiment. Additionally, the electrochemical properties of 6,7-dichloropyrido[1,2-a]benzimidazole-8,9-dione and its α-hydroxy-p-quinone imine derivative as cathode materials were investigated in acidic and neutral environments using cyclic voltammetry measurements. Cathode material based on 6,7-dichloropyrido[1,2-a]benzimidazole-8,9-dione could act as a potentially effective active electrode in aqueous electrolyte batteries; however, further optimization is required.

Keywords

• quinone
• quinone imine
• hydrogen bonding
• X-ray crystallography
• NMR titration
• redox