Novel quinonediimines derived from amino acid-like structures 1: Characterization and DFT computational study: N,N′-bis(5′-benzimidazolyl)-1,4-quinonediimine

Density functional calculations were performed on N,N'-bis(5'-benzimidazolyl)-1,4-quinonediimine, a novel substituted aniline "trimer". This is the first reported symmetric quinonediimine with outer rings derived from amino-acid related structures. Results of the calculations were compared to experimental properties of the herein synthesized trimer. The calculated HOMO levels for isomers of the title compound range from -5.630 to -5.674 eV, and the LUMO levels from -2.889 to -2.924 eV. The calculated electron affinities range from 1.546 to 1.613 eV. The LUMO level is lowest and the electron affinity greatest in magnitude for the syn. syn (outer) isomer. Compared to the widely-studied aniline-capped aniline trimer N,N'-bis(4'-aminophenyl)-1,4-quinonediimine, the title compound has lower LUMO levels and greater electron affinity in both the emeraldine base or emeraldine dihydrochloride form, suggesting that it might be even more effective in corrosion control applications. Because the outer rings are derived from amino-acid related structures, such molecules, particularly as caps in polyanilines, could find use in biomedical applications. (C) 2011 Elsevier B.V. All rights reserved.