title: Mesomorphic, micro-Raman and DFT studies of new calamitic liquid crystals; methyl 4-[4-(4-alkoxy benzoyloxy)benzylideneamino]benzoates.
abstract: The mesomorphic properties of newly synthesized homologous series of calamitic liquid crystals; methyl 4-[4-(4-alkoxy benzoyloxy)benzylideneamino]benzoates, H(2n+1)C(n)OC6H4COOC6H4C(H)=N C6H4COOCH3; n = 6, 8, 10, 12, 14, 16 (MABBAB-n) containing ester and Schiff base groups as linker have been studied by temperature dependent micro-Raman study, differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). All members of this series exhibit enantiotropic smectic A (SmA) mesophase with oily streak and focal conic textures. Analyses of Raman marker bands of phenyl rings, Schiff base and ester groups of MABBAB-10 confirm the phase transitions. The Raman study also gives an evidence of breaking of weak intermolecular hydrogen bonds associated with ester groups and formation of new hydrogen bonds through CN bond at Cr→SmA phase transition. The monomer and dimer were optimized and vibrational assignment of MABBAB-10 was also done with density functional theoretical (DFT) technique to understand the experimental results.
authors.affiliation: Department of Physics, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Rajib
authors.initials: R
authors.lastname: Nandi
authors.affiliation: Department of Chemistry, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Hemant Kumar
authors.initials: HK
authors.lastname: Singh
authors.affiliation: Department of Chemistry, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Sachin Kumar
authors.initials: SK
authors.lastname: Singh
authors.affiliation: Department of Chemistry, Banaras Hindu University, Varanasi 221005, India. Electronic address: bsinghbhu@rediffmail.com.
authors.forename: Bachcha
authors.initials: B
authors.lastname: Singh
authors.affiliation: Department of Physics, Banaras Hindu University, Varanasi 221005, India. Electronic address: ranjanksingh65@rediffmail.com.
authors.forename: Ranjan K
authors.initials: RK
authors.lastname: Singh
mesh_terms: D001565:Benzoates / Q000737:chemistry*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D013059:Spectrum Analysis, Raman
chemical_list: D001565:Benzoates
keywords: Differential scanning calorimetry; Liquid crystals; Polarizing optical microscopy; Raman spectroscopy; Smectic A mesophase