Santanu Chakravorty

Cholesterol-based unsymmetrical Schiff's base dimer terminated with 4-alkoxy-5-phenylthiophene unit: synthesis and characterisation

A series of unsymmetrical cholesterol based dimers have been synthesised and characterised. All the dimers possess a cholesterol unit connected with a 4-alkoxy-5-phenylthiophene unit through Schiffs base linkage. The length of the terminal alkyl and the alkyl spacer has been varied. All the dimers exhibit mesomorphism. Four dimers possess only the cholesteric (chiral nematic, N*) phase. One of the dimers showed smectic A (SmA) and N* phases whereas the other dimer displayed SmA, smectic chiral C (SmC*), N* and twist grain boundary (TGB) phases.

New Efficient RCM-Mediated Synthesis of Pyrrolidine Derivatives

Abstract Fast and effective ring-closing olefin metathesis (RCM) of diallyamine derivatives of coumarin, quinolone, pyridine, and substituted benzene, using first-generation RCM ruthenium-based catalyst, leads to corresponding pyrrolidine derivatives in 70–95% yields under very mild conditions.

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 and characterisation of unsymmetrical six-aromatic ring containing bent-shaped compounds

A new series of achiral unsymmetrical six-aromatic ring banana-shaped compounds has been synthesised and characterised by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. The lower homologue (C6) exhibits an intercalated B6 phase. The middle homologues (C10, C12) form only a B1 phase while higher homologues (C14, C16, C18) exhibit a B2 mesophase.

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 and Characterization of Cholesterol-Based Tetramers

Novel symmetrical liquid-crystal tetramers were designed and synthesized. The length of the central spacer and the outer spacers has been varied. The molecular structures of the target compounds were confirmed by Fourier transform infrared and proton nuclear magnetic resonance spectroscopy. The thermal phase behavior of the tetramers was investigated by polarizing optical microscopy and differential scanning calorimetry. All of the liquid-crystal tetramers showed either a chiral nematic mesophase or chiral nematic and smectic mesophases.

Synthesis and Characterization of Symmetrical Eight Aromatic Ring Containing Bent-Shaped Material Derived from Benzophenone

A new family of symmetrical eight aromatic ring-containing bent-shaped mesogens in which the central elbow is a ketone has been synthesized and characterized. The effect of the side chain on the mesomorphism has been studied. All the bent derivatives were found to exhibit mesomorphism. The higher homologues of the series exhibit the B1 phase and the lower homologues of the series show the B6 phase.