Structural Study of Compounds Modelling Elementary Polymer Units, 6. X-Ray Structural and Quantum-Chemical Investigation of the cis- and trans-isomeric Models of the Polynaphthoylenebenzimidazole Elementary Units

Document Type

Article

Language

eng

Publication Date

2-1994

Publisher

Wiley

Source Publication

Macromolecular Chemistry and Physics

Source ISSN

1022-1352

Abstract

The X‐ray structural investigation of the naphthoylenebis‐(benzimidazole) (1) cis‐ and trans‐isomers as models for the cis and trans elementary units of the corresponding poly(naphthoylene‐benzimidazoles) (PNBI) was carried out. The correctness of the previous identification of the isomers was confirmed, and exact geometrical parameters of the PNBI elementary units (required, in particular, for the calculation of the Kuhn segment of PNBI) were determined. Quantum‐chemical semi‐empirical calculations of the ground and excited electronic states of the isomers were carried out. Both experimental and theoretical data confirm a larger stability of the planar π‐conjugated structure of the trans‐isomer in comparison with the cis‐isomer in the ground as well as in the excited electronic state. Crystals of the cis‐ and trans‐isomers obtained from trifluoroacetic acid solutions are the solvates of bis(trifluoroacetates) of diprotonated 1 with an extremely high content of the solvating trifluoroacetic acid. This peculiarity is favourable for modelling the main characteristics of the interaction between PNBI and protonic polar solvent molecules, viz. preferred types of H‐bonding and a possibility of interaction of the electronic lone pairs of the solvent molecules with the π‐electronic systems of the elementary units of PNBI by charge transfer complexes.

Comments

Macromolecular Chemistry and Physics, Vol. 195, No. 2 (February 1994): 555-570. DOI.

Sergey V. Lindeman was affiliated with the Russian Academy of Sciences at the time of publication.

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