Nandi Rajib, Singh Hemant Kumar, Singh Sachin Kumar, Singh Bachcha, Singh Ranjan K
Department of Physics, Banaras Hindu University, Varanasi 221005, India.
Department of Chemistry, Banaras Hindu University, Varanasi 221005, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2014 Jul 15;128:248-56. doi: 10.1016/j.saa.2014.02.112. Epub 2014 Mar 6.
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.
新合成的一系列含酯基和席夫碱基团作为连接基的棒状液晶——4-[4-(4-烷氧基苯甲酰氧基)亚苄基氨基]苯甲酸甲酯，H(2n+1)C(n)OC6H4COOC6H4C(H)=N C6H4COOCH3；n = 6、8、10、12、14、16（MABBAB-n）的介晶性质，已通过变温显微拉曼光谱研究、差示扫描量热法（DSC）和偏光显微镜（POM）进行了研究。该系列的所有成员均呈现出具有油纹和焦锥织构的近晶A（SmA）相。对MABBAB-10的苯环、席夫碱和酯基的拉曼标记带的分析证实了相变。拉曼光谱研究还提供了证据，表明在Cr→SmA相变过程中，与酯基相关的弱分子间氢键断裂，并通过CN键形成了新的氢键。对MABBAB-10的单体和二聚体进行了优化，并采用密度泛函理论（DFT）技术进行了振动归属，以理解实验结果。
