Nilasish Pal

Bent‐shaped liquid crystals containing a furan bridge in the mesogenic core

We report the synthesis and characterization of hitherto unreported bent‐shaped dimeric liquid crystals based on a furan bridge in the mesogenic core. The compound 18‐Fu2 exhibits liquid crystalline behaviour.

Synthesis, Characterization, and Mesogenic Properties of Anisotropic Imines

Two homologous series of highly anisotropic diimines containing five and six aromatic rings in the mesogenic core derived from 1,4-terephthaldehyde and 4-formylphenyl-4-formylbenzoate have been synthesized and characterized by spectroscopic methods. The liquid-crystalline phases and the phase-transition temperatures are investigated using a polarizing microscope attached to a hot stage and differential scanning calorimetry. Most of the compounds are thermally stable and exhibit smectic and nematic phases over a large thermal range. In the majority of the compounds studied, a SmC phase exists over a very broad temperature range. The importance of the alkyl chain length in competing with the size of the aromatic core in determining the phase variant and in the increase of thermal range of the mesomorphism in a homologous series is described.

Synthesis and Characterization of Unsymmetrical Five-Ring Achrial Banana-Shaped Compounds With a B2 Phase

Two series of unsymmetrical banana-shaped materials have been prepared with laterally substituted hydroxy and nitro groups. All the compounds exhibit liquid crystalline properties. The syntheses and liquid crystalline properties of these compounds are discussed.

Synthesis and Characterization of Banana-Shaped Mesogens Derived From a Benzophenone Moiety

A homologous series of Schiffs bases consisting of a benzophenone moiety as the central core has been synthesized. Schiffs bases were prepared starting from benzophenone by a sequence of reactions, viz., nitration followed by reduction and heating the resulting diamino derivative with 4-formyl-3-hydroxyphenyl 4-(alkyloxy)benzoate. Higher homologues of this series exhibit mesomorphism, but the lower homologues do not seem to possess any liquid crystalline property. The B2 mesophase was characterized by DFT study for orientation of dipole moment. Dipolar interaction and intramolecular H-bonding (N–H) have been considered to discuss the origin of the B2 phase in this homologous series of benzophenone moiety derived systems.

Synthesis of Sulphur Compounds: Regioselective Synthesis of Thieno[2,3-b]thiophenes by Sulfoxide Rearrangement

A number of thieno[2,3-b]thiophenes have been successfully synthesized in a 50–55% yield by m-chloroperoxybenzoic acid–mediated tandem cyclization involving [2, 3] and [3, 3] sigmatropic rearrangements and an intramolecular Michael addition.