Liquid-crystalline properties of unsaturated piperazine-2,5-dione derivatives

Wen Ren Li, Kwo Cheng Kao, Ying Chih Yo, Chung K. Lai

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


The synthesis, characterization, and mesomorphic properties of a new type of liquid-crystalline compounds, (3Z,6Z)-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 1H- and 13C- 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(e)) 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.

Original languageEnglish
Pages (from-to)1400-1407
Number of pages8
JournalHelvetica Chimica Acta
Issue number9
StatePublished - 1999


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