Synthesis, mesomorphic properties and nonlinear optical studies of alkyl and alkoxy phenylacetylene containing phenazine fused extended triphenylene discotic liquid crystalline dyes. (January 2019)

• Record Type: Journal Article
• Authors: Gowda, Ashwathanarayana; Jacob, Litwin; Patra, Alakananda; George, Agnes; Philip, Reji; Kumar, Sandeep
• Is Part Of: Dyes and pigments. Volume 160(2019)
• Page Start: 128
• Page End: 135
• Publication Date: 2019-01
• Subjects: Discotic liquid crystals -- Triphenylene -- Sonogashira coupling -- Columnar phase -- Nonlinear optical transmission; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2018.07.052
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: Herein, we have reported the alkyl and alkoxy phenylacetylene containing phenazine fused triphenylene discotic liquid crystals (DLCs) which are obtained by the condensation reaction of triphenylene-1, 2-diquinone with 1, 2-diamino-4, 5-dibromobenzene, followed by Sonogashira C–C coupling reaction with 4-alkyl-phenylacetylene or 4-alkoxy-phenylacetylene. Six novel derivatives were synthesized and evaluated for their thermal and optical properties. They show a broad range of hexagonal columnar phase and retain their mesophase up to room temperature upon cooling from the isotropic liquid. Thermotropic liquid crystalline properties of all the compounds were studied by polarised optical microscopy (POM), differential scanning calorimetry (DSC). The self-assembly of mesophase structure was investigated by X-ray diffraction (XRD) studies. Thermogravimetric analysis of all the mesogens shows good thermal stability over a broad temperature range. The photophysical properties of newly synthesized compounds were measured using UV–Vis absorption and photoluminescence emission spectroscopy in anhydrous chloroform solvent. The π-extended conjugation in these mesogens exhibit strong absorption bands falling around 270–487 nm and corresponding emission band at 657–663 nm respectively. The high delocalization of π– electrons in extended discotic mesogens show high nonlinear optical properties when measured under excitation by nanosecond laser pulses at 532 nm. These materials may find distinctive applications in the semiconducting devices. Graphical abstract: Image 1