1,3-Dimethyl-5-(3,4,5-tris(alkoxy)benzoyl) barbituric acid derivatives and their liquid crystalline difluoroboron complexes: Synthesis, characterization and comparative investigations of mesomorphic, thermotropic and thermo-morphologic properties

•Mesogenic barbituric acid difluoroboron complexes were synthesized for the first time.•Effect of the chain length on mesomorphic properties has been found.•Mesomorphic, thermotropic and thermo-morphologic properties have been investigated.•Typical textures and microphotographs of the heterophase regions are presented.

A series of 1,3-dimethyl-5-(3,4,5-tris(alkoxy)benzoyl) barbituric acid derivatives 1a–4a with various chain length were synthesized by our group for the first time through the addition of 1,3-dimethyl barbituric acid to 3,4,5-tris(alkoxy)benzoyl chloride at room temperature in presence of pyridine. For preparation of their difluoroboron complexes, the derivatives 1a–4a reacts with borontrifluoride in the presence of triethylamine affording 1b–4b in moderate yields. All derivatives and complexes have been fully characterized by MS, FT-IR and multinuclear NMR spectroscopy. We also explored their liquid crystal properties by using POM, OM, CTW and DSC techniques. The results show that 3b and 4b with longer alkyl chain are monomorphic mesogens and exhibited enantiotropic thermotropic liquid crystalline mesophases. Investigation of their mesomorphic, thermo-morphologic and thermotropic properties is presented in this work.

Graphical abstractA series of 1,3-dimethyl-5-(3,4,5-tris(alkoxy)benzoyl) barbituric acid derivatives and their difluoroboron complexes are synthesized. The mesomorphic, thermotropic and thermo-morphologic properties of these compounds were studied by POM, CTW and DSC techniques.Figure optionsDownload full-size imageDownload as PowerPoint slide