Acid Dissociation Constants of the Benzimidazole Unit in the Polybenzimidazole Chain: Configuration Effects.

The acid dissociation constant of three benzimidazoles, namely 2,2'-bibenzo[d]imidazole, 2,5'-bibenzo[d]imidazole, and 5,5'-bibenzo[d]imidazole, have been investigated by means of density functional theory calculations in gas phase and in aqueous solution. The theoretical approach was validated by the comparing of predicted and experimentally determined p values in imidazole, benzimidazole, and 2-phenylbenzimidazole. From the studied compounds, 2,2'-bibenzo[d]imidazole was found to be the most acidic, which made it a valuable candidate as a material for polymer electrolyte membrane fuel cells.

Effect of benzimidazole configuration in polybenzimidazole chain on interaction with phosphoric acid: a DFT study.

Polybenzimidazole doped with phosphoric acid (PA) is a candidate for polymer electrolyte membranes in fuel cells. Understanding the interaction of benzimidazole in polybenzimidazole with PA is important for fuel-cell applications. Herein, the interaction of a PA-benzimidazole complex was investigated using density functional theory, with calculations performed at the ωB97X-D/6-311G(d,p) level of theory, with an aim to investigate the effects of bibenzimidazole configuration on the interaction energy.

Structural analysis of a banana-liquid crystal in the B4 phase by solid-state NMR.

In this paper, we present a structural investigation of 1,3-phenylene bis[4-((4-10-decyloxyphenyl)iminomethyl)-benzoate], known as a banana-liquid crystal, in the B4 phase, which was performed by solid-state nuclear magnetic resonance (NMR) methodology combined with quantum chemical calculations. The present solid-state NMR measurements including (13)C CPMAS, 2D TOSS-deTOSS, dipole-dephase, 1D and 2D EXSY, and MAS-j-HMQC provided accurate spectral assignments and unambiguous NMR parameters such as (13)C chemical shift tensors, which were used for construction of the three-dimensional structure with the aid of density functional theory calculations. In the obtained molecular structure, two arms of the bent-core molecule are asymmetrically expanded such that the direction of the dipole moment is off alignment with respect to the middle line of the center benzene ring.