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Liquid‐Crystalline Properties of Unsaturated Piperazine‐2,5‐dione Derivatives
Author(s) -
Li WenRen,
Kao KwoCheng,
Yo YingChih,
Lai Chung K.
Publication year - 1999
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19990908)82:9<1400::aid-hlca1400>3.0.co;2-0
Subject(s) - chemistry , piperazine , differential scanning calorimetry , crystallography , alkoxy group , molecule , hydrogen bond , crystallinity , intermolecular force , liquid crystal , carbon 13 nmr , phase (matter) , infrared spectroscopy , organic chemistry , stereochemistry , alkyl , physics , optics , thermodynamics
The synthesis, characterization, and mesomorphic properties of a new type of liquid‐crystalline compounds, (3 Z ,6 Z )‐3,6‐bis(3,4‐dialkoxybenzylidene)piperazine‐2,5‐diones are reported. These compounds were derived from unsaturated piperazine‐2,5‐dione as the core group, and were prepared by condensation reactions of 1,4‐diacetylpiperazine‐2,5‐dione and 3,4‐dialkoxybenzaldehydes. The products were characterized by 1 H‐ and 13 C‐NMR spectroscopy, and elemental analysis, and the phase behavior of these compounds was characterized and studied by differential scanning calorimetry (DSC) and polarization microscopy. The results indicate that these rod‐like compounds exhibit smectic C (S c ) phases. However, for the derivatives with two flexible alkoxy side chains, highly ordered smectic G (S G ) phases were also formed and confirmed by X‐ray powder diffraction. The liquid crystallinity of these molecules was attributed to the presence of intermolecular hydrogen bonds involving the NH groups of the heterocyclic rings. The correlation of phase behavior and molecular shape is also discussed.