Nirupam De

Advances in Metal-Free Heterocycle-Based Columnar Liquid Crystals

Liquid crystals are ordered soft materials formed by self-organized molecules and can potentially be used as new functional materials for electron-, ion- or molecular-transport; optical; and bio-active materials. In particular, the columnar liquid crystals are promising candidates used in various optical and electronic devices. For this purpose, design and synthesis of unconventional materials are essential. In this review, we have summarized several approaches for the synthesis of columnar liquid crystals composed of various heterocyclic systems. We also outline their liquid crystalline and other relevant properties, and their suitability for applications in diverse fields.

Synthesis and mesophase characterisation of a series of new triazine-based disc-shaped molecules

A series of symmetrical disc-shaped materials with a heteroaromatic 1,3,5-s-triazine core and nine alkoxy chains at the peripheral position has been designed and synthesised in a simplified way. All the compounds show hexagonal columnar mesophase. The mesomorphic properties of the compounds have been characterised with the help of polarising optical microscopy (POM), differential scanning calorimetry (DSC) and temperature controlled low angle XRD-experiments.

Palladium-Mediated Bis-Arylation of Inactivated and Activated Arenes

A simple synthetic protocol has been developed for the bis-arylation of unactivated and activated arenes by the implementation of a palladium-catalyzed intramolecular cyclization strategy. The activated arenes give either linearly fused or angularly fused bis-cyclized product depending upon the substitutent present on the nitrogen atom, whereas inactivated arenes give only linearly fused product. The reaction has been carried out in two steps under ligand-free conditions.

Synthesis of 3-iodopyrrolocoumarins via iodine-induced 5-endo-dig electrophilic cyclization

An efficient synthesis of 3-iodopyrrolocoumarins has been achieved by a simple and straightforward strategy involving palladium–copper-catalyzed Sonogashira coupling followed by iodocyclization at ambient temperature using molecular iodine as the electrophilic source. In addition, functionalization at the 3-position of the iodocyclized product is performed via Sonogashira reaction.Graphical abstract

Synthesis of New Nondisk-Shaped Thermotropic Liquid Crystalline Compounds Showing a Rectangular Columnar Mesophase

Linear- and polycatenar-type compounds possessing a cabazole moiety as a head group, linked to the trialkoxy terminal tails via a linear aromatic chain have been designed and synthesized. These compounds exhibit a liquid crystalline rectangular columnar phase. The mesomorphic nature was determined by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) in combination with powder XRD.